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One of the most inexpensive, durable, practical options for roofing material is corrugated board, or, as they say, profiled sheet, metal profile. This is a sheet of metal that is coated with several protective layers, and then passed through a forming machine, which presses projections and grooves into it – to make it more rigid. The material turns out to be quite light, corrugated roofing can be mounted independently and even “in one hand”. The technology is not the most difficult, it is quite possible to do it yourself.
Types of corrugated board
There are different types of corrugated board. There is a regular profiled sheet – galvanized, there is a colored one – with a layer of polymer applied over the zinc coating. The polymer coating has a double role – it both protects against external influences and gives the material a more decorative appearance. Simple galvanized corrugated board is used as a roofing material mainly on temporary buildings, colored has a very solid appearance, it can be seen on the roofs of residential buildings and courtyard buildings.
By appointment
Decking is made from sheet metal of various thicknesses. The thinnest ones are designed for decorating walls, but can be laid on the roof with frequent lathing and small snow loads. The sheets of this group are marked with the letter “C”.
From the thickest metal, a material with increased bearing capacity is made. It is marked with the letter “H”, used as a roofing material in areas with increased wind or snow load. There is also a universal profiled sheet – it is designated “NS”. It can be used both for walls and for roofing (the amount of snow should be average).
After the letter encoding of the profiled sheet, there are numbers: C8, H35, HC20. They indicate the height of the wave in millimeters, which is formed in this material. In the example, these are 8 mm, 35 mm, 20 mm, respectively. A corrugated board with a wave height of at least 20 mm is laid on the roof.
The waveform of the supporting metal profile is often more complex – additional grooves are added to it to increase rigidity.
By type of coverage
With all the external similarity, the price of corrugated board of the same type can differ significantly. The point, most often, is not the impudence of the manufacturer or seller, but the different technologies and materials that are used in production. For example, the protective coating may be zinc and aluminum-zinc. The second type of protection has appeared recently, the equipment is expensive, but the durability of metal coated with aluminum zinc is much higher.
The method of wave formation also affects the durability of the coating. There are two technologies – cold rolling and emulsion. During cold rolling, the sheet is simply pressed through by rollers without any preparation. In order not to damage the previously applied coating, expensive equipment is required. Accordingly, cold rolled profiled sheet is more expensive.
When forming a wave with an emulsion, the metal surface is wetted with a liquid (oil, water, special liquid) and then sent under the rolls. If, after rolling, such a sheet is not dried, but sent to a firing oven to fix the paint, then the places that were wet will quickly begin to rust. It is impossible to see this defect in advance, one has to hope that the technology is not broken. But the profiled sheet made using this technology is cheaper.
There are also different polymer coatings. They create a film of different thickness and density, with different properties.
- Polyester (glossy and matte). Polyester-coated profiled sheet has a relatively low price (the cheapest of the colored ones) and good characteristics – the coating is plastic, does not change its color for a long time. Matte polyester has no glare on the surface, it looks like velvety. This is achieved by a different application technique and a thicker layer. This coating is the most resistant to mechanical damage.
- Plastisol. It has increased resistance to aggressive environments, but does not tolerate ultraviolet light. A corrugated roof with a plastisol coating will fade quickly (two to three years).
- Pural – polyamide and acrylic are added to polyurethane. The coating is more uniform, the service life without color change is from ten years. The disadvantage is the high price.
- PVDF is a compound of polyvinyl fluoride and acrylic. The coating is expensive, but it lasts a long time even in an aggressive environment. This roofing material can be used on sea coasts. Another of its remarkable properties is that it can self-clean. The slightest rain, and the PVDF-coated corrugated roof shines like new.
Under normal conditions, roofing is made of corrugated board with a polyester coating. In terms of price-quality ratio, it is optimal.
How to make a roof from a metal tile, see here.
How to lay corrugated board on the roof
Roofing from corrugated board is laid on a finished crate of boards, in which the fragments are arranged parallel to the roof overhang. The installation step of the crate is up to 60 cm. They usually use an edged inch board, 25 mm thick. Sheets are stacked one after another with vertical overlap on one wave. When laying the profiled sheet on the roof, please note that the extreme shelves have different lengths. The one that is a little shorter should be at the bottom, which is a little longer – it covers the short one. In this case, they adjoin one another tightly, without a gap. If you confuse and do the opposite, then a gap of several millimeters is formed between the two shelves, into which water will flow. Therefore, be careful during installation.
On the amount of horizontal overlap. If there is more than one row of corrugated board on the roof, the sheets are laid with overlap. The amount by which the top sheet overlaps the bottom sheet depends on the angle of the roof slope: the more gently sloping the roof, the more entry is needed.
| Roof pitch | The value of the horizontal overlap of the profiled sheet |
|---|---|
| less than 12° | 200 mm + sealant |
| from 12° to 14° | 200 mm |
| from 15° to 30° | 150-200 mm |
| more than 30° | 100-150 mm |
Most decking factories can offer you sheets that will cover your entire roof – from ridge to eaves – in one long sheet (maximum length 12 meters). During installation, this creates certain difficulties – such sheets are difficult to lift and stack. Especially it will take a long time to expose the first sheet – it must be placed strictly vertically, which is difficult at a height. But the main advantage of such a solution is a continuous coating from top to bottom, which at times increases the degree of protection of the attic from moisture penetration, crosses out all the inconveniences. After all, there are no horizontal joints, which means there are no problems with leakage either.
How to cover the roof with flexible tiles, see here.
How to fix corrugated board on the roof
To fasten the profiled sheet, special self-tapping screws with rubber gaskets under the caps are used. They provide a tight connection. Such self-tapping screws are usually painted in the same tone as the roofing material. The number of fasteners per square meter is 5-7 pieces (do not forget to add about 20% for fastening the ridge element, fixing joints and other similar work).
Self-tapping screws are installed in the lower shelf, where the sheet is in contact with the crate. Their length is 20-25 mm, depending on the thickness of the board of the crate, since it is important that the sharp end of the screw does not protrude from the back of the board. There will be a waterproofing film that can be damaged.
When connecting two adjacent sheets, they are also fastened with self-tapping screws. But in this case, you have to screw the fasteners into the wave, and also punch through a double layer of metal. For these purposes, the fasteners are longer – 40 mm or more (depending on the height of the wave) – the screw must go into the crate board.
What to cut
Very rarely, the installation of corrugated roofing does without trimming – these are just unique cases. How to cut a profiled sheet? Metal shears or electric jigsaw. Yes, it’s slow, and not very convenient, but that’s exactly what the manufacturers advise. It is impossible to use an angle grinder (grinder) – when cut with it, the sheet heats up to very high temperatures at the cut point, which leads to the evaporation of zinc. As a result, in this place, the material quickly begins to rust.
Installation procedure
After assembling the truss system, the front board is nailed, hooks are attached to it for installing the spillway system, and on top of the already special bar – a dropper, on which the edge of the waterproofing film is then wound. Both the dropper and the film are attached to it with self-tapping screws with a sealing rubber washer.
The composition of the pie of materials for corrugated board depends on whether you are going to make the attic space cold or warm. If the attic is cold, the sequence of actions is as follows:
- A vapor-waterproofing membrane is stuffed on top of the rafters. It does not let steam from the house to the roofing, and does not allow moisture that has seeped under the profiled sheet to get into the attic. It is stuffed on the rafters, fastened not at a stretch, but with sagging. Spread the membrane start from the bottom, moving up. One panel comes to the second by 15 cm, the joint must be glued with adhesive tape.
How to install roof waterproofing - The membrane is fixed with planks, which are nailed along the rafter legs. The same strips create the necessary clearance: the membrane must not come into contact with the roofing material.
- A crate (board 100 * 25 mm) is nailed perpendicular to the rafter legs in increments of 50-60 cm. Two boards are attached at the top in a row, on both sides of the ridge – ridge elements will be attached here. In the lower part, where the overhang is formed, two or even three boards in a row are also attached – another dropper is attached here (see the figure above).
- A professional sheet is attached to the crate.
If the roof will be insulated, the order of work and the amount of required materials will change. There will be more layers:
- From the side of the attic, a crate is nailed to the rafters. They will hold the insulation.
- A vapor barrier membrane is attached to the crate with the help of planks (also from the side of the attic), then finishing material can already go.
Approximate composition of a pie for an insulated roof made of profiled sheet - From the side of the roof, the space between the rafter legs is filled with heat-insulating material. Most often it is stone wool and it is better if you find an opportunity to buy material that is not afraid of getting wet (there are some).
- On top of the insulation, a waterproofing film or membrane is attached to the rafter legs. The rules for its installation are the same as described above. But here the task is more complicated: the sagging should be such that the membrane does not come into contact with the insulation. The minimum sag value is 2,5 cm, plus the minimum ventilation gap is 2 cm. If it cannot be provided with the recommended thickness of the insulation, an additional bar is nailed to the rafters, and waterproofing is attached to it. The waterproofing itself is also fastened with slats.
- The crate is being set up.
- The profiled sheet is mounted.
Roofing from corrugated board: knots
Even with a conventional gable roof, there are several complex sections that are usually formed at the junction of different planes and / or parts of the system. These areas are called “nodes”. We considered one such knot in the previous paragraph – the design of the front board and the fastening of drains. But this is far from the only node where a detailed explanation is required.
Installation and sealing of the ridge
The under-roof space under the corrugated board should be well ventilated. This material heats up quickly and also cools down quickly, which contributes to the formation of condensation. Therefore, when installing a metal profile on the roof, in the upper part, the sheets on both sides do not join closely, but leave a gap of several centimeters – so that air can freely escape, taking water vapor with it.
If there are special skates with ventilation (pictured), but even if you just install a regular ridge element between the profiled sheet and its edge, you get a large number of holes – in each corrugation cavity. The size of this gap depends on the height of the wave – the higher the wave, the larger the gaps. On the overhang, where the front board is nailed, there are also similar holes. Air movement usually goes from bottom to top – from the overhang, through the under-roof space (for this, it is necessary to leave ventilation gaps that are formed by the crate when installing the roofing material), to the slots in the ridge. This is how the ventilation and regulation of the humidity of the insulation takes place, the condensate evaporates and is carried away.
Large gaps are good for ventilation, but precipitation clogs in them when it rains / snows with the wind, and dust and leaves get into the attic through them. It is much worse if the holes are clogged with leaves – ventilation will immediately deteriorate. In order not to get into a similar situation, earlier about 2/3 of the height of the gap was filled with sealant, applying it in layers to the roofing material. Crawling back and forth with sealant on the top of the roof, waiting for the previous layer to polymerize a little, is not very convenient. Also, this decision is wrong from the point of view of ventilation – the gap decreases, air movement worsens. But there was no other solution. Now it is – a sealant for corrugated board. It is made from polyurethane foam, polyethylene or wood composite. The structure of these materials is porous, well passes air, but not dust, water or leaves. In shape, it either repeats the shape of the corrugations – there are different types of profiled sheets, and there is also a universal tape, which is simply pressed in the right places.
The sealant “sits” on the sealant, double-sided tape, glue, there are options with self-adhesive tape. With such a seal, air passes freely, and precipitation remains in the outer layers, from where it then evaporates.
Overhang filing with profiled sheet
In order to sheathe the overhang with a profiled sheet, a special profile is attached to the front board. A profiled sheet is inserted into its groove, cut into strips of the desired width. The second edge of the filing is attached to a board nailed to the ends of the rafters. The junction of the filing and the board is closed with two droppers – one is nailed from below, covering the lower half of the board, and the second – from above. The edge of the waterproofing film is then laid on it.
If a drainage system is to be attached, then the hooks for the gutters are nailed after the installation of the lower dripper. The top dropper is nailed after all the hooks are installed.
How to make a valley on the roof, see here.
Adjacency of corrugated board to the wall
In some cases, a metal profile roof is adjacent to the wall of some structure. How to make a connection so that there are no leaks? There are two options (see picture). Both use a corner bar, only it has a different size and a different profile.
You can take a corner bar with shelf dimensions of 150 * 200 mm. A shorter side is brought to the wall, a longer side to the roof They are attached to the wall using fasteners depending on the material from which it is made (nails or self-tapping screws if it is wood, dowels if brick and building blocks). The junction of the plank with the wall is covered with silicone sealant. From the side of the roof, a bar is attached to the crest of the wave by installing special self-tapping screws with rubber washers. Their length is determined in the same way as when connecting adjacent sheets of corrugated board (wave height + 20 mm for entering the crate board).
The second option is more time-consuming: a strobe (groove) is made in the wall, into which an angle bar with shelves bent at 45 ° is inserted. The fastening in this case is similar, the difference is in the dimensions of the bar – it can be 100 * 100 mm or so.
Pipe passage
Many questions arise when sealing the passage of a chimney pipe or ventilation through a corrugated roof. Pipes in cross section are round and rectangular, each type has its own solution.
For the passage of round pipes through the roofing material, there are special steel or polymer aprons. Their upper part is made in the form of a cone, the lower part – a skirt – is made of an elastic material that can take a given shape. The apron is tightly put on the pipe, lowered so that the “skirt” lies on the roofing material. Next, you need to give the elastic skirt the shape of the corrugations. Use a hammer for this (normal or rubber – depends on the type of apron). To prevent water from flowing under the skirt, the joint is smeared with sealant, pressed well.
After fixing the skirt, the neck is fixed. If the apron is metal, the top is covered with a clamp, tightened, the joint is coated with sealant. When using a polymer apron (master flush), it is put on the pipe with a decent effort (sometimes it is even necessary to lubricate the pipe with soapy water), but the joint, nevertheless, for reliability, is sealed.
With a rectangular (brick) pipe, everything is somewhat more complicated. Elements are cut out of metal sheets that close the joint with the roofing pie.