All roofs can be conditionally divided into two categories: roofs with different types of attics and non-attic (combined). These combined roofs are divided into several more varieties: those that are not ventilated and those that are ventilated. In ventilated roofs, there are special voids-layers in which air is exchanged, all this happens under the influence of wind pressure and heat. Attic roofs are divided into three categories, and these are roofs with open, warm and cold attics.
Let's talk about them.
Cold attic
In the 50s of the 20th century, roofs with cold attics began to appear in Moscow. Such roofs were used to equip many residential buildings, other public buildings, and were much more practical than the short-lived bituminous roofs. At this time, semi-passage attics appeared in the city, corresponding to the design of the roofs. Cold loft roofs are designed to allow air from vents to flow directly into the environment. Such vents were called and are called ventilation ducts, they were combined with the help of boxes into small systems in order to reduce the number of partitions, voids in the roof structure, it is more expedient to use carpeted roofs. Such roofs are good in that a certain temperature is constantly maintained in the ventilation ducts, which makes it possible to avoid frost and condensation on the inside of the roof covering panels. Ventilation helps keep the right amount of heat within buildings.
Cold attics are good because:
Excellent waterproofing is carried out due to the small number of protruding elements of the roof, carpet is used sparingly;
Roof repairs and inspections can be carried out directly from the attic;
Attic rooms serve for domestic needs;
Heat from the house is given off in much smaller quantities, due to proper ventilation, maintaining the microclimate.
Warm attic
In such roof structures, attic spaces serve as places for heat exchange and ventilation. They perform all the functions that ventilation ducts perform in cold attics. There is a single common exhaust for warm air, which is sent straight to the atmosphere from the attic. Attic spaces are heated due to the ingress of warm air from apartments into them - the box of such attic spaces is well insulated to avoid heat loss.
Positive aspects of using warm attics:
fewer protruding ventilation elements, which makes the roof more durable;
repair and inspection of attic rooms, being warm;
overall building losses are reduced;
living on the upper floors becomes more comfortable, freezing and leaks are excluded;
the pressure in the ventilation system increases - the productivity of its work increases;
blocks of ventilation ducts are excluded, which simplifies the overall design.
It is important that the sanitary and epidemiological station prohibits the withdrawal of sewer and garbage disposal ventilation into attic rooms. Through the cast-iron exhaust shaft, such waste is removed from the house, located near the ventilation blocks.
33 Drainage from coatings. Installation of a cornice, parapet.
Drainage from roofs can be organized along external or internal drains, and unorganized, with free discharge of water from the overhang of the eaves. Unorganized drainage is allowed to be arranged from the combined roofs of buildings of no more than five floors and without balconies, as well as lawns separated from sidewalks and carriageways. At the same time, it should be taken into account that in three-story buildings and above, with free discharge of water, the moisture content of the walls increases, especially on the windward side, which adversely affects their durability. With the runoff of melt water, ice and icicles form on the overhangs of the cornices, the removal of which often damages the rolled carpet and cornices. In the case when the device of unorganized water removal from the roof is not allowed, a system of organ-bath spillway through gutters and downpipes is arranged. However, in areas with an estimated outdoor air temperature of -5°С, icing forms on overhangs due to the slight slope of the combined roofs. A more perfect constructive solution to this issue is the organization of an internal spillway. This eliminates the possibility of frost on the funnels and ice plugs in the drainpipes due to the presence of ascending flows of warm air in the pipes of the internal drainage system. Internal drains are connected to the storm sewer network or arrange the release of water to the outside. Drainage funnels are located in such a way that the maximum length of the path of water flowing into the funnel does not exceed 24 m and the spillway area per one funnel (with a diameter of the outlet pipe MO mm) does not exceed 80 m2. In any case, there must be at least two funnels on the roof of the building. Drains must be located in such a way that the drainage rough passes next to the partition or wall of auxiliary premises (bathrooms, kitchens, etc.). Eaves are called horizontal profiled protrusions of the wall, designed to drain water falling on the building envelope. The cornice, located on the top of the wall, is called the crowning (or main). The crowning cornice gives the building a finished look. The shapes and designs of the main cornices depend on the architectural design of the building and its dimensions. With small protrusions of the cornice beyond the wall surface (up to 30 cm), it is arranged by gradually releasing several rows of bricks of 5 ... 6 cm each row. Intermediate cornices, which have a smaller extension, are usually arranged at the level of interfloor ceilings, and sometimes under window and door openings. In the latter case, they have an even smaller offset and are called belts. Sometimes separate cornices are arranged above the openings of windows and doors - sandriks, which are usually made from prefabricated prefabricated blocks. If the wall of the building is displayed slightly higher than the crowning cornice, then this part of the wall is called the parapet. The parapet usually has a height of 0.5 ... 1.0 m and can enclose the roof along the entire perimeter or on two or three sides. The device of the parapet allows you to hide the chimneys, ventilation shafts, dormer windows and other superstructures brought to the roof and makes the appearance of the building more attractive.
Central Order of the Red Banner of Labor
research and design institute
standard and experimental design of a dwelling
(TsNIIEP housing) G osgrazhdanstroya
M Moscow Stroyizdat 1986
The thermotechnical calculation of a roof with a warm attic is stated; the areas and conditions of its application are indicated; the technical and economic indicators of the design and the requirements for operation are given.
For engineering and technical workers of design and research institutes.
TsNIIEP developed the dwellings of Gosgrazhdanstroy (Candidate of Technical Sciences A.N. Mazalov). The materials of TsNIIEP of the dwelling of Gosgrazhdanstroy and the results of research by MNIITEP (Candidate of Technical Sciences I.I. Staroverova, engineer I.S. Svidersky) were used.
1. GENERAL PROVISIONS
1.1. A fundamentally new solution for a reinforced concrete roof - the so-called "warm attic" * - was first used in Moscow on residential buildings built according to MNIITEP projects. The attic space of the roof is used in it as a prefabricated ventilation plenum, into which all the ventilation ducts of the residential premises open and the air from which is removed through a common exhaust shaft. The advantages of a roof with a warm attic are: improved ventilation of the upper floors; increasing the reliability of the roof; reduction of heat loss of the upper floor; simplification of the coating design; accessibility for inspection and repair.
* Auth. certificate No. 460365 - "Discoveries, inventions, industrial designs, trademarks", No. 6, 1975
1.2. These Recommendations apply to the design of reinforced concrete roofs with a warm attic for residential buildings from 5 to 16 floors inclusive, built in all climatic regions, using rolled or non-rolled roofing.
1.3. The paper contains recommendations on the construction of a warm attic and the design of its enclosing structures. The design of other structures and engineering equipment, including roofing and ventilation, must be carried out in accordance with current building codes. When calculating the ventilation system, it is advisable to use the recommendations of MNIITEP.
1.4. The attic space of the roof with a warm attic is used as a prefabricated ventilation chamber heated by exhaust ventilation air, therefore, thermal protection and sealing requirements are imposed on its enclosing structures.
The warm attic space should be used for the placement and maintenance of elements of the engineering equipment of the building, as well as for roof repairs.
1.5. The enclosing and load-bearing structures of a roof with a warm attic must comply with the main structures of the building in terms of the materials used, the design solution, manufacturing and installation technology.
The internal surfaces of the walls and coverings of the attic, according to sanitary requirements, are painted with white mineral dyes.
1.6. The use of technical solutions and roof structures that differ significantly from those adopted in these Recommendations is allowed after additional studies and only for experimental construction.
2. DEVICE OF A HEATED ATTIC
2.1. A roof with a warm attic consists of an interior and enclosing structures: an attic covering, external walls and an attic floor. As a rule, the coating is carried out with insulation, the overlap - without it. For a schematic diagram of a roof with various covering solutions, see fig. .
2.2. To ensure air exchange, the attic space is made in the form of a single volume within the planning section of the house. Inside a warm attic, it is not allowed to install isolated compartments with a temperature and humidity regime that differs from the conditions of a warm attic. When using solid internal structures separating the room (supporting panels, high girders, etc.), their total area should not exceed 30% of the attic cross-sectional area.
Rice. 1. Roof scheme with a warm attic
a - covering with a rolled roof; b - coating with rollless roofing;
1 - lightweight concrete covering panel under the rolled roof; 2 - exhaust ventilation shaft;
3 - protective umbrella; 4, 5 - tray panels; 6 - two-layer coating panel with rollless roofing;
7 - outer walls of the attic; 8 - head of the ventilation unit; 9 - internal drain;
10 - support panel; 11 - attic floor; 12 - catchment pan
2.3. Adjacent sections of a warm attic are separated by solid fireproof walls, in which a sealed door measuring 1.5 × 0.8 m or a hatch 0.8 × 0.8 m is arranged.
On the site of the built-in loggias, it is advisable to install the outer walls of the attic in the plane of the facade walls of the house, and lay floor slabs with a layer of thermal insulation above the loggias at the level of the attic floor.
2.5. Entrance to the attic and exit to the roof should be arranged only from the staircase through a fireproof door 1.5 × 0.8 m, installed with sealing gaskets. The entrance to the warm attic is provided in each section of the house, and the exit to the roof is provided in accordance with SNiP II-2-80 "Fire safety standards for the design of buildings and structures" - in the end sections and for every 1000 m 2 of coverage. It is not allowed to arrange access to the roof directly from the warm attic room through a hatch in the roof or through a door in the exhaust shaft.
For access to the attic and the roof, it is recommended to bring flights of stairs to the level of the attic. In buildings with an elevator, access to the roof is through a door in the wall of the staircase and elevator assembly. In buildings without an elevator (and with a lowered machine room), access to the roof is provided through a separate superstructure with a door and a hatch.
All doors and hatches in a warm attic must be equipped with special locking devices.
2.6. The exhaust parts of the sewer risers of the house are combined within the attic section and removed through the exhaust shaft. The pipe of the prefabricated ventilation riser is installed in the corner of the shaft and brought to the level of the wall.
Pipelines of engineering equipment are laid near the warm attic structures at a distance of no more than 0.4 m from the surface of the coating, floor or walls and taking into account convenient access to them.
2.7. The inlet funnel of the internal drain is installed in the middle part of the gutter or valley and is connected to the drain riser by outlet pipes. The pipes of the internal drain within the warm attic are not insulated and are painted with anti-corrosion compounds.
Drainage trays are placed along the average longitudinal axis of the coating, as a rule, at one mark. For all tray solutions, a minimum height must be provided under them (see p.). The slope of the roof towards the tray is provided by the inclined laying of the roofing panels.
2.8. It is advisable to illuminate the warm attic room with natural light through openings in the upper half of the outer wall. The light openings are filled with hollow glass blocks, which are usually installed in two rows (layers) in the plane of the wall. With a single-layer filling, the heat loss of light openings is taken into account in the heat engineering calculation. The area of the openings is taken equal to 1 - 2% of the overlap area. It is not allowed to use bindings with window glass to fill light openings.
2.9. It is not allowed to place consoles and mechanisms for suspension of repair cradles inside the warm attic. They are recommended to be installed on the attic floor, which is calculated for an additional load.
3. DEVICE OF THE VENTILATION SYSTEM
3.1. In panel buildings with a warm attic, unified ventilation units with prefabricated main ducts to the height of the building and bypass ducts to the floor height should be used. According to a similar scheme, ventilation ducts are made in brick and block houses.
The dimensions of the ventilation ducts in the blocks should be such that the maximum air flow on one floor exceeds the minimum flow on the other by no more than 1.3 times. In this case, exhaust fans for the kitchens of the upper floors are not installed.
To release air from the channels into the warm attic, special heads are installed on the ventilation blocks of the upper floor, which act as an air flow diffuser. Separate channels from the upper floor should be left in the heads.
3.3. Air is released from the warm attic into the atmosphere through a common exhaust shaft, one for all apartments in each section of the house or an isolated part of the attic. The device of a combined exhaust shaft for apartments of different sections of the house is not allowed. The exhaust shaft is located in the central part of each section of the attic, at approximately equal distances from the ventilation blocks. The shaft is installed, as a rule, on the attic floor, outside the gutter, and the shaft inlet is located at the level of the lower surface of the floor. It is not allowed to lower the walls of the shaft to the attic floor with the installation of side holes in them.
With a rectangular section of the hole in the plan, the ratio of the long side to the short side for a free-standing shaft should not exceed 1.5, and for an attached shaft - 2.
Rice. 2. Ventilation unit head for duplex installation
a - cross section; b - top view; 1 - concrete head;
2 - ventilation ducts of the upper floor; 3 - prefabricated channels from kitchens and bathrooms;
4 - attic floor panel; 5 - ventilation unit
4.4. Internal roof support structures are usually made of flat concrete panels installed above the internal load-bearing walls of the building. The support panels are made with holes of such dimensions that the opening of the structure is at least 50%.
4.5. It is recommended to attach the exhaust shaft to the wall of the machine room of the elevator, while the shaft should be 0.5 m higher than the cover of this room. When installing a free-standing shaft, its stability in the wind must be ensured. The exhaust shaft rests on the bearing structures of the roof or supporting elements of the attic.
The exhaust shaft is made in the form of a prefabricated space box of a rectangular or round shape (see Fig. ), with insulated or non-insulated walls. In the absence of a catchment pan under the shaft (see p.), its walls must have thermal protection of at least 0.7 of the calculated thermal resistance of the coating, for which it is recommended to make them from expanded clay concrete panels with a concrete layer. If there is a pallet, the walls of the shaft can be made uninsulated, but made of dense frost-resistant concrete (see p.) with a minimum wall thickness of 60 mm.
Rice. 3. Scheme of the device of the exhaust ventilation shaft
a - with a roll roof; b - with a rollless roof; 1 - covering panel with a rolled roof;
2 - junction of a rolled roof; 3 - concrete wall of the mine; 4 - non-rolled coating panel;
5 - waterproofing; 6 - protective metal apron; 7 - pallet supports;
8 - extract from sewer risers; 9 - catchment pan;
10 - twist for condensate drainage; 11 - attic floor
It is allowed to use exhaust shafts with a metal frame sheathed with sheets of asbestos cement on one side (non-insulated) or on both sides (with internal filling with heat-insulating material).
A protective umbrella made of reinforced concrete slab or asbestos-cement sheet is installed on metal racks above the shaft at a distance equal to 0.7 of the hole width, with an overlap in each direction over the edge of the shaft by 0.4 of the hole width. If necessary, additional protection of the shaft with louvered grilles or wind deflectors may be provided.
The drainage pan, welded from metal sheets and painted with anti-corrosion compounds, is installed with a gap on the ceiling along the waterproofing layer (Fig. ). The depth of the pallet is assumed to be 0.15 - 0.3 m (depending on the intensity of showers in the area), the size in the plan corresponds to the size of the shaft opening, increased by 0.3 m in each free side. It is possible to use pallets made of other durable materials, including dense waterproof concrete. The drip tray is usually not connected to the building's drainage system and water is removed from it by evaporation.
In areas with particularly unfavorable climatic conditions, it is allowed to install a catchment pan in combination with a protective umbrella.
5. LOFT COVERING STRUCTURES
5.1. The covering of a warm attic consists of panels of high factory readiness, combining load-bearing, heat-shielding and waterproofing functions and made in the form of a single structural and assembly element. The coating panels are made non-ventilated, and their normal wet state is ensured by the location of the protective layers and the limitation of the initial moisture content of the insulation (see paragraphs; and).
It is forbidden to use building-made coatings (with backfill and monolithic layers) that have low performance properties and high labor intensity.
5.2. According to their functional purpose, the coating differs: coating panels (roofing panels), forming inclined surfaces (slopes) for water drainage and tray panels (trays) for collecting and diverting atmospheric water into the internal drainage system.
The attic covering should be solved, as a rule, according to the longitudinal structural scheme, with the support of the roof panels on the gutter and the outer walls of the attic, with the panels symmetrically arranged relative to the gutter.
The design of the attic cover should provide freedom of temperature deformations at the joints of the panels and at the support nodes.
In this case, rigid connections are not placed at the top of the panels.
Cover panels and trays are designed, as a rule, to be bent according to a beam scheme, with a relative deflection of not more than 1/200 of the span. It is not recommended to use continuous structures in prefabricated roofing.
The covering panels have a constant thickness along the entire length and are usually reinforced with conventional reinforcement.
5.3. Depending on the type and method of waterproofing, the attic flooring is performed:
with rolled roofing - from layers of rolled roofing material (roofing felt), sequentially glued at the construction site;
with a mastic roof - from layers of waterproofing mastic (including reinforced) with protective properties that are not inferior to a roof from a standard roofing material;
with a rollless roof - from mastic and painting waterproofing materials that perform protective functions together with waterproof and frost-resistant concrete of the panel;
with a concrete roof - made of weather-resistant concrete that performs all protective functions without additional surface waterproofing.
Rice. 4. Coating structures with roll roofing
a - from single-layer solid panels; b - from single-layer panels with thermal inserts;
insulation; e - using ribbed roofing slabs; g - using a multi-void
flooring; 1 - panel made of load-bearing lightweight concrete; 2 - roll roofing; 3 - sealing gasket;
4 - concrete key; 5 - rigid plates of effective insulation; 6 - layers of dense concrete;
7 - lightweight concrete of low density; 8 - layers of heavy concrete; 9 - pouring thermal insulation;
10 - thermal insert of the joint; 11 - multi-hollow flooring; 12 - protective layer of concrete;
13 - ribbed roof panel
In some cases, instead of factory production of special panels (Fig. , a - d), it is advisable to manufacture panels based on the available standard designs of industrial-type ribbed roofing slabs (Fig. , e) or multi-hollow flooring (Fig. , g), on top of which in polygon conditions heat-insulating and protective layers with the above characteristics are laid. When the thickness of the concrete shelf of the supporting roofing slab (Fig. , e) is less than 40 mm, a vapor barrier layer of roofing felt or film is glued under the insulation.
Rice. 5. Coating structures with rollless roofing
a - from two-layer solid panels; b - from panels with thermal inserts;
c - from three-layer panels with low-density concrete; g - from three-layer panels with effective
insulation; e - from multi-hollow panels with different thermal insulation; 1 - roofing layer of concrete;
2 - a layer of load-bearing lightweight concrete; 3 - concrete flashing; 4 - sealing gasket;
5 - rigid plates of effective insulation; 6 - a layer of dense concrete;
7 - lightweight concrete of low density; 8 - layer of heavy concrete; 9 - transverse voids;
10 - pouring thermal insulation
At the joints of panels for rolled roofing (Fig. ), it is recommended to make a concrete key in the lower third of the panel thickness and install a sealing gasket on the mastic at the mouth of the joint with filling the middle part of the joint with a heat-insulating insert.
In a three-layer panel with porous expanded clay concrete (Fig. , c), its density is assumed to be 800 - 900 kg / m 3, and the strength of the lower layer must be at least B-15.
The concrete of the lower layer and load-bearing ribs of a three-layer panel with effective insulation should have the same minimum strength (Fig. , d). To reduce thermal inhomogeneity, the thickness of the insulation in the panel (Fig. , d) is assumed to be at least 100 mm when using materials according to the type (Fig. , b).
For the future, a coating solution is proposed from multi-hollow panels (Fig. , e), which, with a unified design solution, can have a different amount of thermal protection. The latter is provided by internal air voids, filled, if necessary, with monolithic thermal insulation made of efficient materials (foaming foam). The voids are placed in the expanded clay concrete layer of the two-layer panel according to (Fig. , a).
A reliable solution for the joint of rollless panels is to cover it with a U-shaped reinforced concrete lining for the entire length of the panel (Fig. ) Sealing seals are installed in the lower and upper parts of the joint, the middle part of the joint is filled with soft insulation. Other joint protection and sealing solutions must pass production and operational testing.
5.7. Drainage trays, which are an integral part of the rollless coating, are usually solved in the form of trough-shaped panels, in which the slope of the bottom to the drain funnel is formed by a variable thickness (60 - 150 mm) of the concrete roofing layer. Lateral longitudinal ribs carry the load from the roofing panels, and the end ribs serve to form a joint and organize overflow, for which the middle part of the end rib is lowered or a notch is made in it. The upper part of the tray (bottom and ribs) is made of the concrete of the roof layer, while the lower part repeats the decision of the type of roofing panel in which the tray is used.
Overlapping gutter solutions (“cascading” gutter solutions) do not provide maximum attic dimensions and increase the product range.
The minimum width of the tray is determined by the width of its open area (between the drain fins at least 900 mm) and, with the decisions of the tray assembly (see p. ), is 1800 mm.
The minimum value of the indicator (brand) at
rollless roofing (paint waterproofing)
concrete roof (without surface waterproofing)
Compressive strength class
Tensile strength class
Waterproof brand
Water absorption by mass
Frost resistance grade above -15 °С:
in the outdoor range from -15° to -35 °С
five-day temperatures below -35 °С
In addition, concrete of the roofing layer without surface waterproofing must have increased crack resistance (shrinkage and temperature); moisture resistance (moisture-drying cycles) in hot and humid areas; heat resistance (heating - cooling cycles) in hot dry areas, as well as corrosion resistance in the atmosphere of industrial cities.
Waterproofing applied at the factory on the top surface of non-rolled panels must meet the following requirements:
compressive strength not less than 0.5 MPa;
adhesion to concrete at a shear of at least 1.0 MPa;
frost resistance not less than 100 cycles;
water resistance at a pressure of at least 8 atm;
heat resistance (on a vertical surface) not lower than 90 °C;
relative elongation at 20 °C not less than 200%.
Rice. 6. Solutions for cornice and tray assembly in rollless coating
a - eaves knot; b - tray assembly; 1 - end rib; 2 - concrete flashing;
3 - sealing gasket; 4 - drain rib of the panel; 5 - drainage tray;
6 - supporting console of the tray; 7 - cover panel; 8 - outer wall;
9 - trimming the panel (with a single wall height)
It is also recommended to carry out the eaves assembly with the overlapping of the covering panel on the outer wall, with the protection of the end of the panel by a cantilever extension of the roofing layer with an increase in the end rib (Fig. ). If necessary, the cornice unit is made with a parapet 200 - 600 mm high, which is formed by a continuation of the wall panel, covered from above with a reinforced concrete L-shaped stone.
In order to maintain a constant mark of supporting platforms on the walls in the cornice unit and a uniform slope of the coating when changing the width of the body, it is recommended to cut the lower layer on the supporting section of the coating panels, which for existing projects does not exceed 90 mm.
5.10. The non-rolled covering of a warm attic can be designed on the basis of other constructive solutions and insulating materials, in compliance with the proven principles of the device (see paragraphs ; ; ). Such pavement structures must undergo production and operational testing in experimental construction.
The main direction of the subsequent improvement of the attic coating should be the maximum lightening of structures through the use of effective structural and heat-insulating materials. It is advisable to cover solutions with single-layer concrete panels on porous aggregates, which have increased strength, heat-insulating and waterproofing properties, including panels on tension cement. Panels with internal voids filled with monolithic thermal insulation, including panels made of extruded asbestos cement, as well as reinforced cement sheets, can be considered promising designs.
6. THERMAL ENGINEERING CALCULATION OF A HEATED ATTIC
6.1. The heat engineering scheme of a warm attic is a mobile interconnected system, the calculation of which is carried out according to winter conditions to determine the minimum heat loss of the building or the minimum heat protection of the coating.
The basis of the heat engineering calculation is the provision of sanitary and hygienic conditions of the dwelling, the observance of the heat balance of the unheated attic space and the inadmissibility of condensation on the inner surface of its external fences.
The heated air of the exhaust ventilation of the house and the heat coming through the attic floor should be taken as heat sources. If necessary, heat emissions from heating and hot water pipelines are also taken into account. Attic heat loss is calculated through the coating and external walls.
according to the condition of ensuring the sanitary and hygienic condition of the premises of the upper floor, the minimum allowable air temperature in the attic is found
At a low temperature of the inner surface of the coating, it is necessary to determine the air temperature in the attic according to the condition of inadmissibility of condensate:
In the calculation formulas () - () the following designations are accepted:
Heat transfer resistance of the attic floor and the outer wall of the attic, m 2 ·°C / W;
- heat transfer coefficient of the inner surface of the ceiling and coating, W/(m °C);
D t n - normative temperature difference at the inner surface of the attic floor, °С;
t in ; t n - temperature of internal and external air, °С;
t veins - temperature of the air entering the attic from the ventilation ducts, °С;
q veins - specific heat input to the attic with ventilation air, W / m 2 · ° С;
F st - reduced area of the outer walls of the attic.
1. SNiP II-L.1-71*. residential buildings;
The heat transfer coefficient of the inner surface of the coating when calculating according to the condition of inadmissibility of condensate is recommended to be taken according to the experimental values given in Table. .
table 2
|
Coating inner surface |
Floors of the house |
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|
Ribbed |
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|
With partitions |
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When constructing a gutter, the values of the coefficients should be taken according to clause 3 of the table. .
Rice. 7. Design temperature of the inner surface
t until- main cover; t cold- cold area
The average temperature of the coldest five-day period with a probability of 0.92 is taken as the design temperature of the outside air (SNiP 2.01.01-82. Construction climatology and geophysics). When calculating a warm attic for residential buildings of 12 floors or more, according to the condition of inadmissibility of condensate, the calculated outside temperature can be taken according to the average temperature of the coldest period (SNiP 2.01.01-82. Building climatology and geophysics). In this case, the required temperature regime is provided due to the large thermal inertia of the roof with a warm attic.
The temperature of the inner surface of the coating is determined from the condition of the inadmissibility of condensate at the calculated outdoor temperature and depending on the moisture content of the air in the attic (see p.). The permissible minimum temperature value is recommended to be taken according to the graph in fig. .
The temperature of the air coming from the ventilation ducts is recommended to be increased by 1 ° C relative to the calculated air temperature in living rooms according to (SNiP II-L.1.-71 *. Residential buildings).
Specific heat inputs with ventilation air are defined as the ratio of the product of air consumption (according to the norms of exhaust from residential premises SNiP II-L.1.-71 *. Residential buildings), (m 3 / h) and its heat capacity of 1 kJ / (kg ° С ) and density (1.21 kg / m 3) to the attic area (m 2). For preliminary and general calculations, it is recommended to take the value according to Table. (with security 0.8)
The area of the outer walls of the warm attic is determined according to the design data and is reduced to 1 m 2 of coverage. For preliminary and general calculations, you can take the value of the reduced area equal to 0.4, which corresponds to the end section with a wall height of 1.75 m.
Table 3
|
Specific heat inputs with ventilation air in houses (W / m 2 ° С) |
|||
|
gasified |
electrified |
||
|
Thermal resistance of the snow layer, m 2 ° C / W |
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Intermediate values are interpolated and, taking them into account, the actual heat transfer resistance of the cold section is determined, according to which the temperature of the inner surface of the coating is checked. With snow cover, condensation on the surface of the cold area is excluded.
The calculation of enclosing structures for this case is carried out according to the condition of inadmissibility of condensate in the following sequence:
in accordance with the established procedure (see p. ) using the formulas () and (), the resistance to heat transfer of the coating is found, for which, according to the formula (), the minimum air temperature in the attic is calculated according to the condition of inadmissibility of condensate; in this case, the outside temperature is entered with a value that cannot be lower than the initial value by more than 10 °C;
at the minimum temperature in the attic, the refined heat transfer resistance of the insulated attic floor is determined
(7)
When installing additional insulation on the floor, the thickness of the layer of a given material is found by the formula
(8)
where l ut - coefficient of thermal conductivity of the insulation material (according to the "A" condition), W/m °C.
The calculation ends with a check using the formulas () and () of the actual air temperatures in the attic and outside with the performance, if necessary, of repeated clarifying calculations.
The thermal capabilities of a 5-storey building allow, by insulating the attic floor, to reduce the estimated outside temperature by 10-15 ° C, which, on average, does not reach the required temperature level for the attic of a 9-storey building by 3 ° C on average. Therefore, the use of a unified coating panel is not always possible.
6.7. The thermal efficiency of a roof with a warm attic is expressed by a decrease in the heat loss of the attic floor relative to the normalized (SNiP II-L.1-71 *. Residential buildings) value of 35 W / m 2 (30 kcal / m 2 h).
If it is necessary to reduce the total heat loss of the building to the control ones (Gosgrazhdanstroy. Target indicators of specific heat consumption for heating residential buildings - Order No. 419 of 12/28/83) or specified indicators, the heat engineering calculation of the roof is carried out with minimal heat loss, for which the reduced value of the heat flow through the ceiling is determined:
(9)
where ∆ q F - a given value for reducing the specific heat consumption relative to the control indicator, W/m 2 of the total area;k- coefficient of reduction of the area of the attic floor to the total area of the house, taken 0.27 for a 5-storey building and 0.16 for a 9-storey one.
The heat flux value is entered in the formula () instead of the equivalent expression D t n α in . The resulting air temperature in the attic cannot be equal to or higher than the internal temperature, therefore, in further calculations, a value lower than the internal temperature by at least 2 °C is used. The corresponding increase in thermal protection of the coating caused by a decrease in heat loss should be checked in accordance with SNiP II-3-79. Construction heat engineering and other economic calculation at reduced costs.
I climatic region
II - III climatic regions
IV climatic region
Floors of buildings
Roof with roll roofing over attic paneling:
single-layer solid (bearing expanded clay concrete)
single-layer with effective thermal liners
using ribbed roofing slabs
using multi-hollow flooring
Roof with rollless roofing and attic paneling:
two-layer (heavy concrete and bearing expanded clay concrete)
two-layer with effective thermal liners
three-layer (with expanded clay concrete of low density)
three-layer (heavy concrete and effective insulation)
Note. The following symbols are used in the table: P - preferred use is recommended; D - it is allowed to apply when justifying; N - not allowed to use.
Table 6
|
Reduced costs, rub. |
Operating expenses, rub. |
Labor intensity, man-hour |
Consumption of materials, kg |
||||||
|
Total |
estimated cost |
capital investments |
Total |
including heating |
general |
at the construction site |
cement |
steel |
|
|
Roofs with roll roofing |
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|
Single layer 250 mm of expanded clay concrete 1100 kg / m 3 |
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Single layer 250 mm with 50 mm styrofoam thermal pads |
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Roofs with rollless roofing |
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Two-layer 250 mm with expanded clay concrete 1100 kg / m 3 |
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Double layer 250 mm with foam inserts 100 mm |
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Three-layer 250 mm with expanded clay concrete 800 kg / m 3 inside 150 mm |
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Three-layer 250 mm with foam insulation 150 mm in reinforced concrete |
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Multi-hollow 250 mm with cast foam (100 mm) |
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7.4. When choosing a design for a preliminary assessment of various solutions, it is recommended to use the technical and economic indicators of various designs for covering a warm attic, per 1 m2 of the total area of a 9-storey building, given in Table. . The types of roofs and panels adopted in it correspond to Table. and fig. 5v
By cost
By labor intensity
7.5. To ensure the design conditions for the operation of the ventilation system of the house and the enclosing structures of the warm attic, the roof must be operated in compliance with the mandatory rules for maintenance and service. In matters of technical operation of roofs, one should be guided by the instructions of these Recommendations, for which purpose the explanatory note to the project should briefly state the main conditions for their proper operation.
7.6. To exclude disturbances in the operation of the ventilation system of buildings, all doors and hatches of entrances and exits to the attic, as well as in intersection partitions, must be securely closed during ventilation. To do this, they provide for the installation of special locking devices that exclude their opening by unauthorized persons.
Lighting of the attic space must be provided at any time of the day, for which the electrical wiring of the scoop is connected to the emergency lighting network.
7.7. When accepting houses for operation, the correct installation and connection of ventilation blocks and ducts, as well as the cleanliness of the ducts and heads, should be checked. During operation, you should constantly monitor the condition of the channels and heads, preventing them from clogging with debris and dust. It is allowed to install protective nets and gratings on the heads, with cells of at least 50 mm in size.
7.8. Cleaning of the warm attic space should be carried out in case of a noticeable accumulation of dust sediment on the floor from the waste ventilation air. The frequency of cleaning is determined by the intensity of dusting. Cleaning is carried out dry - using vacuum cleaners or wet - using moistened brushes and rags. Wet cleaning of a warm attic by washing the floor and walls with water jets is not allowed, due to the lack of waterproofing and drainage devices in the ceiling.
During operation, the attic floor should be regularly cleaned of dirt, especially drainage trays and water intake funnels.
Snow removal is allowed to be carried out in separate areas only in case and place of leaks. When cleaning the coating, it is forbidden to use crowbars, steel shovels and scrapers.
7.9. Control over the technical condition of the roof should be carried out through scheduled, general and partial inspections, and, if necessary, extraordinary ones. Periodic general reviews are held in autumn and spring, inside the attic and outside the roof. Extraordinary inspections are carried out after particularly strong winds, heavy rains and snowfalls, as well as a period of extreme natural temperatures.
When inspecting roofs, the main attention should be paid to the following:
safety of the roof (rolled and non-rolled) on the coating;
the state of the surface of the roofing reinforced concrete elements (with a non-rolled roof);
tightness of joints of roofing elements;
the condition of parts and components of the coating (drain, cornice, etc.);
the condition of the drainage devices.
7.10. To eliminate concrete defects that occurred during the operation of rollless roofing elements, a partial repair of the surface is carried out by clearing the exfoliating section of concrete, treating it with a polyvinyl acetate suspension of PVA and applying a layer of polymer-cement mortar to restore the destroyed panel profile. Cracks that have appeared in concrete are also sealed with a polymer cement mortar, while a crack with an opening of more than 0.2 mm is preliminarily cleared. To seal cracks in the gutter, it is advisable to use epoxy compositions.
Restoration of paint waterproofing should be carried out at intervals and according to the technology provided for by the technical specifications for the relevant materials.
BIBLIOGRAPHY
1. Guidelines for the design and installation of reinforced concrete roofs with rollless roofing for residential and public buildings / SibZNIIEP. - M.: Stroyizdat, 1979. - 39 p.
2. Guidelines for calculating the humidity regime of building envelopes / NIISF Gosstroy USSR. - M.: Stroyizdat, 1984. - 168 p.
3. Guidelines for determining the estimated cost and labor intensity of manufacturing precast concrete structures at the design stage. Structures of residential and public buildings / NIIES, NIIZhB, TsNIIEP dwellings. - M.: Stroyizdat, 1977. - 81 p.
4. Rules and norms for the technical operation of the housing stock / Minzhilkommunkhoz RSFSR. - M.: Stroyizdat, 1977. - 260 p.
5. Reinforced concrete roofs of multi-storey residential buildings: Obzor / TSNTI. - M., 1982. - Issue. 8. Constructions of residential and public buildings. - 64 p.
All roofs according to their design features can be divided into two types: combined-non-attic and attic. Combined roofs, in turn, are divided into ventilated (with drying layers or grooves) and non-ventilated. In the cavities of the interlayers of ventilated roofs, air exchange must occur, with the help of wind and thermal pressure. All attic roofs are divided into three types: cold attic, warm attic and open attic. Let's consider each type in detail.
Cold attic roofs
Roofs with a cold attic began to be built in Moscow from the mid-fifties of the twentieth century. Roofs of this type were then erected over many residential and public buildings, since this type gave a guarantee (in comparison with bituminous) for many years of operation. Also at the same time, roofs with a semi-passage attic appeared in Moscow. The design of roofs with a cold attic provides for air from ventilation ducts to enter directly into the atmosphere. Why the channels within the sections are combined with the help of ventilation ducts to reduce the number of intersections of the roof and the rolled carpet. Thus, a certain temperature is maintained in the attic by natural ventilation, which prevents condensation and the formation of frost on the lower surface of the roof panels. Such ventilation significantly limits heat loss from the premises of the building.
The advantage of a cold attic roof:
Heated attic roofs
In this roofing system, the attic floor is not thermally insulated - the closed volume of the attic room independently performs the duties of a prefabricated static pressure ventilation chamber. Ventilation air entering the warm attic from the premises is removed into the atmosphere through a common exhaust. The entire volume of the attic is heated by warm ventilation air from the premises, which is why the enclosing structures of such an attic must have increased thermal protection and be carefully sealed.
Advantages of roofs with a warm attic:
Important! According to sanitary and hygienic requirements, exhaust pipes of the sewerage and garbage chute, channels from the technical underground are not displayed in the attic. Exhaust parts of sewer risers - to be combined within the attic with cast-iron pipes and removed with one pipe through the exhaust shaft. The exhaust shaft for the release of air into the atmosphere is installed in the middle at equal distances from the ventilation units.
Open attic roofs
In the construction of a roof with an open attic, the attic floor is thermally insulated, and outside air enters it through holes 700x300 mm in size, located along the perimeter of the attic with a step of 1 m. This air is removed through the exhaust. The principle of operation of an open attic is that a mass of dry outside air enters the attic space and removes moisture from the premises. A feature of the open attic is the combination of warm and cold attic systems.
Advantages of open attic roofs:
But a roof with an open attic, unfortunately, has a number of significant drawbacks, such as:
Such inconsistency of properties shows that roofs with an open attic are best used in southern regions. Intensive ventilation of the attic space removes overheating of the upper floors from solar radiation, when the reinforced concrete coating works as a continuous sunscreen.
A separate type of roof can be distinguished as a non-rolled reinforced concrete roof - this design has an impassable, semi-passable or walk-through attic and a coating of special reinforced concrete elements. The design of the rollless floor does not have an attic, it is replaced by a coating of reinforced concrete elements that perform enclosing and heat-insulating functions, and protects the premises from atmospheric influences. In non-rolled roofs, waterproofing compounds only protect the concrete surface of the coating from premature destruction by the atmosphere, and the water resistance of the joints of the roofing panels and their interface with the enclosing structures is solved by constructive methods. Rollless reinforced concrete pavement consists of supporting elements - trusses, frames, pitched beams, etc. and reinforced concrete slabs under mastic waterproofing insulation. Rollless reinforced concrete roofs are divided into:
According to the method of drainage- with a central drainage tray made of separate trough-shaped panels, three-sided panels and a funnel tray with a drain funnel; with water-collecting trays located at paraprtny walls; with external unorganized drainage system.
By type of mating roofing slabs- with sides located above the shelf of the roofing panel; with grooves along the edges of the roof panels.
According to the method of adjoining roofing slabs to frieze panels- with the use of additional elements; with removal along the edges of the building to the frieze panels.
Roof panel design- single-layer from heavy or light concrete; multilayer or with heat-insulating liners; with conventional reinforcement.
Description:
In the vast majority of cases, residential buildings are equipped with a natural ventilation system. It is known that the main disadvantage of these systems is the low available pressure. Therefore, as a rule, if the exhaust air is discharged through ventilation shafts, to which exhaust air from apartments is supplied through collection ducts, then a lot of problems arise with the ventilation of the upper floors: it is difficult to reconcile the available available pressure, determined by the insignificant height of the shaft (1 m above the roof), with rather large aerodynamic resistance of prefabricated channels and shafts with an umbrella. As an element of the natural exhaust ventilation system, a warm attic appeared in the 1970s.
Ventilation of residential buildings with a warm attic
Flow rates through exhaust grilles and supply valves at different outdoor temperatures and in the attic, the doors are closed
The dwelling house is served by natural ventilation systems with double-sided connection of satellites to the shaft and unregulated exhaust grilles. In all apartments, regardless of size, the same ventilation systems are installed, because in the building under consideration, even in three-room apartments, air exchange is determined not by the inflow rate (3 m 3 / h per m 2 of living space), but by the exhaust rate from the kitchen , bathroom and toilet (total 110 m 3 /h). The height of the exhaust shaft above the floor of the warm attic is 6 m.
Calculations of the air regime of the building were performed for the following outdoor temperatures: 5 °С (calculated for ventilation); -3.1 °С (average heating season in Moscow); -28 °С (calculated for heating) with wind at a speed of 0 m/s; 3.8 m/s (average for the heating period); 4.9 m/s (calculated for window density selection).
The air temperature inside the warm attic during the calculated winter period (at t n = -28 °С) was changed from 18 to 5 °С (the issues of water vapor condensation were not considered), in the middle of the heating period at an outdoor air temperature of -3.1 °С, the temperature in the attic, 19 and 10 °C were equated, and at a design temperature for ventilation of 5 °C, respectively, 20 and 12 °C.
The calculation results showed that at an attic temperature of 20 °C, during the calculation period for ventilation (t n = 5 °C and calm weather), the adopted ventilation system with ventilation units and supply valves on the upper floors does not provide standard air exchange of 110 m 3 / h (due to the narrowed sections of the ventilation network trunk and due to the installation of supply valves instead of open vents provided for by the ventilation calculation). On fig. 2 shows the change in air flow through the ventilation grills and supply valves along the height of the building in various weather conditions at various air temperatures in a warm attic. These results refer to a two-room apartment of two-way orientation.
From fig. 2 it can be seen that a moderate drop in air temperature in a warm attic (to the temperatures indicated above) has practically no effect on the air exchange of apartments on the lower floors and slightly (by 10-15% at t n = -28 ° C and by 20-25% at t h = 5 °C) reduces the air exchange of the upper floors. It is clear that with a slight available pressure for the upper floors during the calculated period for ventilation in calm weather, a reduction in available pressure due to a decrease in temperature in a warm attic is undesirable, but not fatal. With the wind, the air exchange of the apartments of the upper floors located on the windward facade and double-sided apartments increases, the decrease in the temperature of the warm attic affects much less even for the upper floors.
In a building without a warm attic, with exhaust shafts rising 3 m above the floor of a cold attic, air exchanges are slightly lower than in a building with a warm attic, as can be seen from Fig. 3.
Unauthorized opening of the doors from the staircase to the warm attic at t n = -28 °C has little effect on the operation of the ventilation system, as follows from Fig. 4. Additional opening of the doors to the apartment on the top floor, to the apartment hall, to the stairs, to the street also does not lead to significant changes. When calculated for ventilation t n \u003d 5 ° C and no wind, the effect of door opening is also small. However, when the wind appears and the door to the attic is opened, cases of overturning ventilation on the upper five floors are very likely.
 |
Figure 4 Air flow rates through exhaust grilles with different options for opening doors to the attic at an outdoor temperature of 5 °C 1 - in the absence of wind, closed doors to the attic 2 - at a wind speed of 3.8 m / s, closed doors to the attic 3 - in the absence of wind and an open door in the attic 4 - in the absence of wind, an open door to the attic, in the apartment and in the hall 5 - in the absence of wind, an open door to the attic, to the stairwell and at the entrance to the building |
These results do not cancel the desires, generally recognized for all types of natural ventilation systems, to competently design the ventilation system itself and have individual fans in individual channels for the last floors. At the same time, it is desirable to keep in mind that when installing supply valves, the resistance of the ventilation tract increases and the number of upper floors where fans are needed can increase to four.
conclusions
1. The natural ventilation system in residential buildings with a warm attic can operate without tipping over even if the air temperature in the attic drops to 5 °C during the calculated winter period (at t n = -28 ° C) and during the calculated period for ventilation at outdoor temperature 5 °С to 12 °С.
2. Opening doors to the attic has little effect on the ventilation of apartments during the entire heating period in calm weather. In the presence of wind, overturning of ventilation on the upper five floors can be observed at outdoor air temperatures above 0 °C.
Literature
1. SNiP 2.08.01-89*. Residential buildings. 1999.
2. MGSN 2.01-99. Energy saving in buildings. Standards for thermal protection and heat and water supply.
3. Biryukov S. V., Dianov S. N. Expanding the capabilities of the AIR program for calculating the air regime of a building // Modern systems of heat and gas supply and ventilation. Sat. tr. MGSU. M.: MGSU, 2003.
Page 17 of 20
7. ROOFS
Roof structures
The entrance to the attic and the exit to the roof are recommended to be arranged from the staircase through a fireproof door measuring 1.5 ´ 0.8 m. In this case, it is recommended in all cases to provide exits to the roof in the end sections.
7.2. Attic reinforced concrete roofs are divided into:
according to the thermal regime of the attic - with a cold (including open) and a warm attic;
according to the method of removing air from the exhaust ventilation of the building - on the roofs with the release of air from the ventilation to the outside (cold attic) and with the release of air from the ventilation into the attic space (warm and open attic);
according to the design of the coating - from reinforced concrete slabs (without thermal insulation or insulated slabs) of the coating;
by type of roof - rolled and non-rolled with protective mastic (painting) waterproofing or without it (with weather-resistant concrete).
In the roof with cold attic(Fig. 56) the internal space is ventilated with outside air through openings in the walls, the cross-sectional area of \u200b\u200bwhich with a reinforced concrete coating must be at least: in I and II climatic regions - 1/500, in III and IV - 1/50 of the floor area. In a roof with an open attic, the area of the ventilation openings in the walls is determined by thermal engineering calculations for winter and summer operating conditions.
Rice. 56. Roof scheme with a cold attic
a b¾ covering with rollless roofing
1 2 3 - reinforced concrete drainage tray; 4 - base panel; 5 - floor panels; 6 - a layer of insulation with a protective layer; 7 - supply and exhaust openings in the walls; 8 - block of ventilation ducts; 9 - insulated internal drain pipe
With a pitched roof made of piece materials, the attic space is ventilated through the gaps between its sheets, therefore, in climatic regions I and II, ventilation openings can be reduced to 0.01.
With a roof with a cold open attic (Fig. 57), thermal insulation is laid on the attic floor slabs. It is recommended to protect the heat-insulating layer along the perimeter of the attic to a width of at least 1 m from moisture. Ventilation shafts and hoods of sewer risers in a cold attic must be insulated above the attic floor.
Rice. 57. Roof scheme with an open attic
a- covering with a rolled roof; b
1 - reinforced concrete roofing panel for rolled roofing; 2 - reinforced concrete roofing panel with rollless roofing; 3 - reinforced concrete drainage tray; 4 - floor panels; 5 ¾ support panel; 6 7 8 - ventilation hole in the outer wall; 9 - a layer of insulation with a protective layer; 10 - insulated pipe of the internal drain
In a roof with a warm attic (Fig. 58), the attic space, which has insulated frieze outer walls and insulated roofing, is heated by warm air that comes from the exhaust ventilation of the house. To remove air from the attic space, exhaust shafts should be provided, one for each section. The attic space should be sectioned by walls into isolated compartments. Doorways in the walls, providing a through passage through the attic, must have sealed porches. To protect the exhaust ventilation shafts from atmospheric precipitation in a cold attic, it is recommended to install protective umbrellas over them.
Rice. 58. Roof scheme with a warm attic
a- covering with a rolled roof; b- covering with rollless roofing
1 - lightweight concrete covering panel for rolled roofing; 2 - the same, tray; 3 - a two-layer covering panel with a non-rolled roof; 4 - the same, tray; 5 - support panel; 6 - floor panels; 7 - solid outer walls; 8 - head of the ventilation unit; 9 - exhaust ventilation shaft; 10 - protective umbrella; 11 ¾ drainage pan; 12 - internal drain
Roofs with a cold attic are allowed to be used in residential buildings of any number of storeys. Roofs with a warm attic are recommended for use in buildings with a height of 9 or more floors.
The admissibility of using roofs with a warm attic in buildings with a height of less than 9 floors must be justified by a feasibility study. In buildings with a height of less than 5 floors, roofs with a warm attic are not recommended,
Ventilation units with channels passing through the attic with air outlet to the outside must be at least 0.7 m above the level of coverage (with a roof slope of up to 10%).
In roofs with the release of ventilated air into the attic space, which acts as a static pressure ventilation chamber, the exhaust is carried out through the exhaust shafts, and on roofs with an open attic, there are also ventilation holes in the frieze walls.
The reinforced concrete covering of the attic roof consists of pitched slabs, which form inclined surfaces for atmospheric water drainage, and tray slabs, which serve to collect and drain atmospheric water into the internal drainage system.
For roofs with an internal drain, it is recommended to install at least one drain funnel in the roof tray slabs for each section. Drainpipes and pipes within a cold attic should be insulated. In low-rise buildings with an external unorganized drain (in buildings with a height of 1 - 2 floors), it is necessary to place the building with an indent from the red line by 2 m, with the installation of canopies over the entrances and balconies.
7.3. Roofs made of piece materials are recommended to be made of asbestos-cement sheets, tiles or other similar materials.
Roll roofing is made from layers of rolled roofing materials, which are glued to the coating elements in construction conditions.
For rolled roofs, it is recommended to use roofing felt according to GOST 10923-82 (roofing felt with coarse-grained dressing, lining roofing felt with powdered or fine-grained dressing), roofing glassine (GOST 2697 - 83), glass roofing felt (GOST 15879-70), roofing felt deposited (TU 21- 27-53-76), rolled insulation (GOST 10296-79) and rolled fiberglass mesh from alkali-free glass.
The lower layer of the rolled roof is recommended to be partially glued to the base, including from perforated roofing felt (“breathing roof”). In the case of using continuous roll materials, it is recommended to glue them to the base in stripes or spots on an area of about 30% . In all cases, the roofing carpet should not be glued along the joints of the slabs on a strip 25 cm wide. When using roofing material with coarse-grained dressing in the top layer of the roofing carpet, it is allowed not to arrange a protective layer of gravel in I - III climatic regions.
In a roof with a non-rolled roof, the concrete of the roof panel performs the protective function, protected by hydromastics applied to the upper surface of the panel, as a rule, in the factory.
Waterproofing protective mastics for non-rolled roofs must have adhesion to concrete, retain strength and elasticity in the range of operating temperatures in accordance with the specifications for these materials. Mastic and painting compositions must meet the following requirements: compressive strength of at least 0.5 MPa, shear adhesion to concrete of at least 1 MPa, frost resistance of at least 100 cycles, water resistance at a pressure of at least 0.8 MPa, heat resistance of at least 90 ° С, relative elongation at 20 °С not less than 200%.
The concrete from which the panels for the rolled roof are made must meet the requirements specified in Table. 18 for panels with protective mastic paint and without surface waterproofing.
Table 18
Characteristics of concrete slabs | The minimum value of the concrete index |
|
coatings | with protective mastic coloring | without waterproofing (weather-resistant concrete) |
Compressive strength class of concrete | ||
Tensile strength concrete class | ||
Concrete grade for water resistance | ||
Concrete grade for frost resistance at the outside temperature of a cold five-day period, ° С: | ||
above minus 15 | ||
from minus 15 to minus 35 | ||
below minus 35 | ||
In roofs with a rolled roof, the slope of the slopes must be at least 5%, in the catchment trays - at least 2%. The design of the roofing panel must ensure the absence of cracks on the upper surface with a protective color under operational conditions, and for panels without waterproofing - even at the time of stripping the product. The upper front surface of roofing panels must comply with category A2 according to GOST 13015.0-83 for panels with a protective color and category A1 - for panels without waterproofing.
7.4. Reinforced concrete elements of the attic (roofing slabs and tray slabs) are recommended to be designed with support on both sides. The use of non-cut structures is not recommended.
Roof slabs are recommended to be supported on external walls and tray slabs located along the middle axis of the building. For external non-load-bearing walls in the plane of the external walls, it is recommended to provide for the installation of reinforced concrete beams supported on the load-bearing transverse walls of residential floors.
The adopted scheme of supporting the prefabricated elements of the coating must ensure the freedom of thermal deformations of the coating or its parts. At the same time, the stability of the roof structures should be ensured.
7.5. With roll roofing, roofing slabs are designed with a smooth top surface. At the joints of the slabs, it is recommended to provide for the installation of concrete dowels.
7.6. In case of rollless roofing, it is recommended to design joints of roofing slabs with side ribs at least 10 cm high, covered with concrete flashings. In places where roofing slabs rest on the gutter, it is recommended to form a cantilever overhang at least 30 cm long with a drain rib along the edge. In case of rollless coating, it is recommended to support the roof panels on the outer walls with the formation of an overhang. If necessary, the cornice unit is made with a concrete parapet.
Prefabricated elements are recommended to be manufactured in an inverted position (“face down”) and transferred to the working position with the help of tilters. To ensure the required performance of concrete in terms of frost resistance and water resistance, it is recommended to use vibro-impact technology for the manufacture of roofing elements and provide for heat and moisture treatment according to the "soft mode".
7.7. Roof slabs with a cold attic are recommended to be designed in the form of thin-walled reinforced concrete ribbed panels: ribs down - with a rolled roof and ribs up - with a rolled roof. The thickness of the roof slab flange is recommended to be at least 40 mm, and the thickness of the rollless tray is at least 60 mm.
Warm attic floor slabs with roll-free roofing must have an upper roofing layer of at least 40 mm made of dense concrete and side ribs 100 mm high. Plates are recommended to be designed in two layers, including those with heat-insulating inserts.
It is recommended to design roof slabs of a warm attic under a rolled roof as single-layer lightweight concrete, including those with thermal inserts or three-layer ones.
7.8. Attic floor slabs are recommended to be designed similar in design to interfloor ceilings.
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