- Flat roof structure
- Technology advantages
- Which SIP to choose
- Armo-belt and carrier system device
- Floor installation
- What to look for
The flat roof attracts with the reduced consumption of materials and the ability to exploit additional usable area for a wide variety of purposes. Our site offers to consider one of the possible options for a flat roof – using structurally insulated panels (SIP).
Flat roof structure
It is generally accepted that the construction of walls and ceilings is the only purpose of self-supporting insulated wire. However, the strength and load-bearing properties of this building material are sufficient to withstand not only snow but also limited operational loads. An incompressible filler structure in a double-sided rigid shell has almost the same mechanical load-carrying model as a reinforced concrete product. This greatly facilitates the calculation of the structural strength..
There are two techniques for constructing a flat composite roof. The first involves the use of panels in a shell made of wood-based materials with a mineral wool filling. The panels are laid on a frame support system, waterproofing, distance lathing and roof covering are sequentially arranged on top. Technologically, this option is more complicated, the influence of the human factor is too great, but the quality of the materials used has a minimal effect on the final result. As a rule, a roof of this design is cheaper..
The second type of flat roof consists of panels in a metal sheath. Roofing galvanized iron is covered with decorative and protective polymer layers, in fact, the outer shell is a profiled sheet. Such panels are much longer and can cover spans up to 6 m long.With such a roof structure, a lot depends on the quality of the protective and decorative coating, the correct profile of the locks, and the availability of adequate sealing means.
The device of any roof made of SIP panels belongs to the category of fast construction; often an average object can be covered in two work shifts, that is, during a summer daylight hours, if you do everything yourself. Moreover, the service life of most of these roofs is more than 50 years..
The main advantage of a flat roof made of panels is good heat-saving qualities. Air convection is completely eliminated, while the thickness of the insulation can reach 250-300 mm, due to which you can feel in absolute comfort under the composite roof, even being in the northern region with severe winters. It is very important that the roof is filled with insulation at the factory, and any cold bridges are completely excluded.
Although, in general, the possibility of constructing a flat roof from self-supporting insulated wire does not depend on the type and structure of the walls, the internal climate control system can dictate its conditions. The panels are impermeable to steam and gases, respectively, humidity and carbon dioxide in the premises will constantly accumulate. We’ll have to seriously attend to a well thought-out ventilation device, but this is absolutely standard practice in modern construction. Another feature is that the weight from the roof must be distributed over all the walls, which in stone buildings is realized by pouring an armored belt, and in frame buildings – due to crossbars and supporting trusses.
Which SIP to choose
Buying panels of the required type is the first item in the instructions for installing a composite roof. Depending on the properties of the material, a different installation scheme can be used, and the set of technical solutions also differs. The required panels are called roofing panels; only two types are suitable for the purposes under consideration.
If the roof is supposed to be covered with weld-on insulation, bitumen shingles, folded sheets and other materials suitable for use at low slopes, it is better to give preference to panels with a double-sided OSB class 3 or 4 sheathing. It is very important that the binder of the inner shell of the panels is synthetic wax, while the outer ones should be impregnated with urea-formaldehyde resins. This is the best option, but other variations are possible, you just need to remember that the inside of the panels should not emit volatile substances.
The metal panels form the almost finished surface of the rough ceiling and the complete roof covering. The main difference between such materials is the type of protective coating (Pural, Plastisol, PVDF are the most preferred) and the design of the connecting lock. The latter must have a counter-board to prevent moisture seepage into the joint, or be designed for rolling. In many imported panels, instead of a mechanical valve, a system of sealing strips is used, but there are not many high-quality materials on the domestic market..
Only PUR, mineral wool and polyisocyanurate must be used as insulation. The use of PPP for roof insulation is not allowed in any form. The quality of the insulation on the slab cut is the main sign of the quality of the entire material. It should be free of large cavities, crumbling areas, and wrinkles. In this case, it is recommended to check the uniformity of filling by sticking a thin metal knitting needle along the plate.
Armo-belt and carrier system device
In terms of time, the most costly stage in the construction of a flat roof is the construction of a supporting system for supporting panels. In some cases, the length of the material is sufficient to cover the entire opening entirely, however, it is necessary to achieve an even distribution of the load on the side walls, and, if necessary, strengthen the joints.
For buildings made of bricks and block materials, an armopoyas device is recommended. Unlike the final crown under the ceilings, such a structure is cast along the inclined formwork. Both sides must be aligned strictly parallel.
First, the formwork is filled to the level of the lowest point of support, and it takes about 2-3 hours to set. After the side, the side tapes are covered with OSB covers 1–1.5 m long, depending on the slope. Armopoyas is poured in stages, simultaneously moving the covers to the upper part. On days 2–3 after pouring, it is necessary to remove the burrs from the tape and grind off large irregularities flush with the formwork. Armopoyas is a serious thermal bridge, in order to reduce heat loss, the concrete tape is separated by longitudinal partitions made of expanded polystyrene, respectively, the reinforcing frame is knitted in several parallel lines.
In frame buildings, powerful square girders are laid on the upper and lower walls, which must cover the entire thickness of the enclosing structure. Energy-efficient transoms are often found with vertical staggered perforations. After the formation of the upper and lower lines, which form the plane of the support, they are connected to each other by single-pitched trapezoidal trusses. To form an inclined plane above the crossbars, a bar is attached to them from above, cut to fit a wedge-shaped profile.
If the length of the panels is not enough to cover the entire span, support beams with a contact patch width of at least 200 mm must be mounted along the joining lines. In stone buildings, metal trusses or steel I-beams are used, whichever is more economically feasible. In wooden houses, support is provided by trusses with a counter-oblique filling. If necessary, the support of the beams themselves can be made with steel pipes or uprights made of timber, which are subsequently hidden in the thickness of the capital partitions.
A flat roof slab is a fairly simple system. In the case of panels in wood sheathing, they are fixed to the support system using galvanized steel corner brackets. Before installing the next panel, several longitudinal cords of mounting glue-foam are applied to the ends. If the joints can be fastened with overhead strips from the bottom side, waterproofing can be immediately attached to the outer surface and the roof covering can be mounted. Otherwise, you must first install a continuous crate: OSB under the profiled sheet, folded iron and bituminous tiles, or glass-magnesite slabs under the overlaid roof.
It is easier to mount metal panels: the locks at their ends provide sufficient strength of the joints, but at the same time the joints must be sealed. Depending on the manufacturer’s recommendations, sealing can be performed either using the same glue-foam, or by laying rubber-polymer PSUL.
What to look for
When installing panel roofing, it is very important to ensure proper protection of the ends of the cake. For wooden panels, it is made with OSB sheathing: the plate is cut into boards with a width of the thickness of the panel, and then fastened to screws and bitumen mastic. It is necessary to ensure that the shell is absolutely airtight, for which it will also not be superfluous to smear all longitudinal and transverse seams with mastic.
For metal panels, the upper and side ends are sealed with L-shaped or U-shaped wind strips made of roofing iron. Transverse joints often have a metal overhang, but it is important to ensure that the length of the overlap is not less than the allowable for the existing slope. The bottom joint is closed by a U-shaped strip, one of the edges of which is not seamed: with it, the overlay is inserted into the body of the panel close to the upper metal shell to a depth of 100-150 mm. From below, the strip adjoins the outer plane of the shell and is attached to it with self-tapping screws with a sealing washer.
As a rule, the upper and longitudinal ends of the panels are slightly displaced inward relative to the outer plane of the walls. At the same time, a straight parapet is erected on the sides and on top, which will ensure the integrity of the facade and additional protection of the roof pie. But at the same time, it is imperative to cover with ebb strips the junction of the panels to the roof flange.