- Roof supporting system
- Insulation and protection of the roof
- Sheathing device for corrugated board
- How to sew the cover correctly
- Skate and overhang protection
Due to the large format, the roofing corrugated board allows you to quickly perform roofing of even very large sizes. The durability of the polymer-protected steel is also not questioned. In this material, we will consider the features of the process of arranging a roof from corrugated board.
Roof supporting system
Profile sheet is a fairly light roof covering that does not require a continuous sheathing. Therefore, the rafter system is arranged using basic methods according to the technology corresponding to the type of roof.
For flat and pitched roofs, a system of sloping trusses in the form of a rectangular trapezoid or triangle is assembled. The material can be a wooden beam or a shaped steel pipe of square section. To give rigidity, the truss chords are connected by a set of braces.
For gable roofs with a slope of up to 25 °, a system of several rows of portal or shed trusses is assembled. This design implies the absence of an attic space, but allows a significant span..
For residential buildings, the roofing systems described above are rarely used; preference is given to more standard structures of the attic, gable or hip types. The material of the rafters is mainly wooden boards placed on the edge. Massive ribs form a hollow skeleton, which allows the construction of an attic or attic, and then the system is strengthened with uprights and guy wires according to the calculation of the snow load and its own weight.
Insulation and protection of the roof
The profiled sheet practically does not impede the outflow of heat, but at the same time retains water vapor. In habitable premises, the roof is made in the form of a “cake”, which includes one or more layers of insulation, as well as special membranes that protect the insulation from wind erosion and moisture accumulation.
The choice of insulation material must be approached very carefully when it comes to covering from corrugated board. Stone wool of different types is the most economical option, but it is very sensitive to moisture saturation and requires a properly thought-out ventilation of the under-roof space with protection of the insulation from water vapor.
Various kinds of polymer insulation practically do not absorb moisture and work well even at the border of high and low temperatures. But in summer operation, not entirely obvious problems may arise. So, foam plastic (PSB) and expanded polystyrene (PS), familiar to many, when heated above 70 ° C, significantly lose their physical and mechanical properties and are subject to more active destruction with the release of increased portions of styrene and the formation of an unpleasant odor.
Without shading, the roof in the summer heat is quite capable of heating up to 90 ° C, therefore, direct contact of the roofing with polymer insulation should be excluded. In part, the issue can be solved by laying a space for blowing, as is done to ventilate mineral wool heaters with street air. But the width of the air gap should be quite high, about 120–150 mm, so in some cases it makes sense to separate the roof and insulation with heat-resistant gypsum fiber or magnesite plates.
Magnesite glass sheets
Heaters based on stone wool should be used in an outdoor environment, because in most pies they are separated from the internal atmosphere of the premises by a vapor barrier – a membrane that allows air to pass through, but retains steam. Residual moisture penetration is eliminated by ventilating the insulation, due to which the water evaporates quickly and does not have time to harm the cotton wool. To exclude the formation of condensation on the inner side of the vapor barrier, the point of condensation of steam is shifted into the insulation according to the data of the heat engineering calculation.
Sheathing device for corrugated board
For the reasons described above, a profiled sheet roof requires a rare horizontal lathing. For non-insulated buildings, this requirement arises from the installation technique of sheets placed vertically.
In the presence of insulation, a small air gap is necessary when using any type of insulation, because the outer layer, one way or another, is arranged from a hygroscopic material, resistant to heat, but sensitive to moisture saturation.
Roof device made of corrugated board. 1. Profiled sheet. 2. Ridge corner. 3. Rafter system. 4. Sheathing. 5. Vapor permeable membrane. 6. Counter lattice. 7. Insulation – mineral wool
The practice of housing construction shows that it is reasonable to use wooden beams 40–60 mm thick for horizontal lathing. This makes fastening the sheets easy and is good for compensating for linear thermal expansion..
The table shows the values of the permissible pitch of the crate depending on the size of the corrugated board used and the slope of the roof.
Corrugated board Roof slope Sheet thickness, mm Lathing step S-8 >15 ° 0.5 solid S-10 <15 ° 0.5 solid >15 ° 0.5 up to 300 mm S-20 <15 ° 0.5-0.7 solid >15 ° 0.5-0.7 up to 500 S-21 <15 ° 0.5-0.7 up to 300 >15 ° 0.5-0.7 up to 650 NS-35 <15 ° 0.5-0.7 up to 500 >15 ° 0.5-0.7 up to 1000 N-60 not less than 8 ° 0.7-0.9 up to 3000 N-75 not less than 8 ° 0.7-0.9 up to 4000
If the roofing system and the lathing are made of dissimilar materials, rigid fastening of all parts is required, for which bolted connections are used. The difference in durability is also due to heterogeneity, therefore, the wood used must be impregnated with antiseptic and insecticidal compositions, and painted before installation.
How to sew the cover correctly
The technique of laying corrugated board is in many ways similar to the flooring of slate with a few exceptions. Installation is carried out strictly in rows upward from the bottom of the slope. The first row is lacing with an overhang over the protruding clipped ends of the rafters from 10 to 25 cm.
Fastening of sheets, unlike many wave materials, is carried out not in the ridge, but in the lower wave. To exclude the seepage of rain and melt water, special self-tapping screws with a rubber washer are used to seal the puncture site. The tightening force must be carefully controlled: the pinched washer quickly dries up, and the mount loses its tightness.
The second and all subsequent rows are superimposed on the previous one along the wave and with an overlap corresponding to the length of the sheet and the step of corrugation. The specific value is indicated by the manufacturer individually for each format.
The last row often requires a short edge trimming. The sheets are cut with special scissors, because cutting with an abrasive disc leads to a violation of the protective coating up to 10 cm from the cut. Trimming is performed in such a way that at the convergence of the two upper rows there is a gap for the outlet of the roof ventilation. The sheets of the upper row are placed with the edged edge up to hide the places of processing with protective mastic under the ridge profile.
Fastening of roofing elements made of profiled sheet. 1.the extreme upper and lower row along the profiled sheet is fixed along each lower ridge to the crate. 2. the intermediate rows of bindings are staggered across the wave. 3. The ridge profile is attached with self-tapping bolts to the upper crest of the corrugated sheet wave.
Skate and overhang protection
For roofing made of profiled sheet, a wide range of additional fittings is provided, designed to protect slopes converging on the ridge, wind and eaves overhangs. The fittings are made of the same material as the sheet, in the color of the main coating. Often, the bending of fittings is performed in-place from polymer-coated sheet metal.
A set of additional elements for corrugated roofing
The greatest difficulty in working with corrugated board is the convergence of the slopes in the valleys. Before stripping the sheets, a continuous crate is arranged in them, on which wide trays of galvanized or polymerized steel are attached. When sewing on the sheets, a distance of 15–20 mm is maintained between the cut edge and the center of the valley. Cut protection is performed with bitumen mastic, Movil or nitro paint, then the abutment is covered with a decorative corner profile.
Skate protection is performed with an angular profile, the turn of which corresponds to the slope of the slopes. A very common universal profile that has several fold lines. The ridge segments are fastened with an overlap of about 20 cm, and a sealing tape made of foamed polyethylene is laid 20–30 mm from the edge. The open edges of the skates are protected with end caps.
Overhangs on cornices and pediments are sewn up with bent products from polymerized sheet, here all the advantages of using manual bending machines are manifested. On the eaves overhangs, the metal is attached to the projections of the rafter boards or to the crate stuffed on them, if the step is not frequent enough. The entire filing box is under the roof covering.
Wind overhangs on the gables are closed with U-shaped overlays. They cover the edge of the roof covering by 10-15 cm, which often has to be cut due to minor differences in the geometry of the roof. Lining is attached on both sides: through the coating and to the inside of the crate, often the edge of the longer part is folded back onto the pediment for a more technologically advanced abutment.