- Types of roofs. What type of roof is suitable for metal tiles
- Calculation of the amount of material
- Installation of metal tiles
- Thermal insulation
- Vapor barrier
- Ventilation of the roof space
- Installation of lathing
- Installation of metal tiles
Metal tiles are one of the most beautiful and durable roofing materials. What shape of the roof to choose in order to prevent overspending of material, how to calculate the required amount of metal tile and how to properly mount it, is described in this article.
Metal tiles are one of the most popular roofing materials. A beautiful appearance, solidity and durability are the main characteristics, because of which they choose the metal tile, while often not thinking about whether it is advisable to use it. The biggest problem here is the large amount of waste when used on complex roofs. How to find out how much waste there will be, how to calculate the amount of tiles required to equip the roof and how to mount it all correctly? Let’s figure it out.
Types of roofs. What type of roof is suitable for metal tiles
First you need to figure out on which roofs it makes sense to put metal tiles, and on which it is not worth it. The following main types can be distinguished.
1. Single slope.Consists of one rectangle plane.
2. Gable.Consists of two planes-rectangles, one for each slope.
3. Broken line.Consists of four planes-rectangles, two for each slope.
4. Hip.Consists of four ramps, one for each side. Two slopes are triangles, the other two are trapezoids.
5. Tent.It looks like a hip, only all slopes are triangles with one common vertex.
6. Multi-pinch.In fact, it consists of 2 or more gable, hip, etc. roofs, forming a complex, sometimes multi-level, structure.
Metal tiles are rectangular sheets with pronounced top-bottom sides, that is, you cannot use an inverted sheet, as possible, for example, with slate. Therefore, when building a roof made of metal tiles, after diagonal trimming, a lot of waste is often obtained. To understand why this is happening, let’s unroll the indicated types of roofs..
A sweep is a visual representation of the shapes that form the slopes. As mentioned above, pitched, gable and sloped roofs are formed from rectangles. It is clear that assembling a rectangle from rectangular sheets is a trivial task. Consider other types of roofs.
Hip – two triangles and two trapezoids, hip – four triangles, multi-plucked – triangles, trapezoids, rectangles and parallelograms. Let’s draw them and break them into rectangular pieces (metal sheets). So, the hip roof:
It is quite obvious that no matter how the ramp breaks, in any case after receiving pieces 1, 4, 5, 6, 7, 8, 9, 12, pieces 1A, 4A, 5A, 6A, 7A, 8A, 9A, 12A will remain. Is it possible to apply such leftover pieces somewhere? Cut off piece 1 from the whole sheet, 1A remains. No matter how we twist it, it will not fit in place 4, or 5, 6, 7, 8, 9, or 12, that is, it is waste. This will be true for the rest of the leftover pieces. Consider a parallelogram ramp:
It can be seen that after receiving piece 1, the remainder will go to location 6, and the remainder from 7 to location 12.
Thus, a parallelogram ramp by itself will not give waste, but any other (with the exception of a rectangular ramp, of course) will give one or another percentage of residues that, ultimately, will become waste. Parallelogram ramps are found only on multi-plucked roofs. Hip and hip-roof such elements do not have.
So, when deciding whether a metal tile is suitable for your roof, you need to pay attention to the shape of the roof. Single and gable roofs, as well as a sloping roof formed from rectangles are an excellent option for metal tiles. Anyone else will have waste. For hipped roofs, their number as a percentage of the entire material is maximum. Hip – slightly less. For multi-gable roofs, it is rather difficult to say unequivocally. You can make a house with a roof that will not have waste, or you can make a house that will have even more of them than a house with a hipped roof. To estimate their number in each specific case, it is necessary to break the entire roof surface into the simplest shapes:
Everything is clear with rectangles. Triangles. If in the process of unfolding, paired triangles are not obtained, forming a rectangle and having the correct direction, then each will give as much waste as it is itself. If the percentage of residues exceeds 30% of the total amount of material, then using metal tiles for such a roof is irrational.
Calculation of the amount of material
Let’s start by determining the number of sheets of metal tiles. Distinguish between full and useful sheet sizes. Useful ones determine what actual area the sheet will cover. It is these dimensions that should be taken into account when calculating the number of sheets of metal tiles per slope. Full is a useful plus overlap. It is different for different manufacturers. Vertical – 0.1, 0.12, 0.13, 0.15 m, etc., horizontal – 0.06, 0.08, 0.09 m, etc. The size of the overlap does not affect the calculations. The length of a sheet of metal tile is strictly tied to a step equal to the wavelength, that is, 0.35 m. Accordingly, the useful length of the sheets is 0.35, 1.05, 2.1 and 3.5 m, that is, for the 1st , 3, 6 and 10 waves – these are the necessary dimensions for calculating the number of horizontal rows. The useful width of sheets is different for different manufacturers – 1.05, 1.1, 1.14 m, etc. – this is the required size for calculating the number of vertical rows.
For a rectangular slope, the amount of metal tile is calculated as follows: in width – the width of the slope is divided by the useful width of the sheet. Round up. We get the number of sheets in a horizontal row. By height – divide the slope height by 0.35 m. Round up. We get the number of waves. It must be remembered that if the slope of the slope is less than 14 °, then the overlap must be done in two waves, that is, to the total number of waves it will be necessary to add a number equal to the number of rows minus 1. Determine with which sheets this quantity can be paved. We get how many and which sheets of tiles in a vertical row. After that, we multiply by the number of rows in width. Bottom line – how many and which sheets of metal tiles are needed for this slope.
Example. We have a slope measuring 9×5 m. Determine the number of rows in width. We take a tile with a width of 1.05 m.We get: 9 / 1.05 m = 9 rows. The remainder will have to be cut – this is waste. To make them smaller, you can play with the size of the gable overhang. Determine the vertical sheets: 5 / 0.35 m = 15 waves. If the slope angle is more than 14 °, then 2 rows of 6 waves and one 3 waves will be optimal. If less, then, remembering the overlap, do row 10 and row 6 waves, respectively.
Conclusion: for a given slope with an inclination of more than 14 °, you need 18 sheets of 6 waves and 9 sheets of 3 waves. For a slope with an inclination of less than 14 °, you need 9 sheets of 6 waves and 9 sheets of 10 waves.
To calculate the triangular areas of the roof that do not have a pair, and trapezoids, we finish each figure to a full rectangle and calculate according to the above scheme. If paired triangles are formed, then we take this into account. Parallelograms are calculated as rectangles with one side equal to the base and the other equal to the height of the parallelogram.
The number of other elements of the roof is determined separately:
- Ridge elements – cover the ridge (the place where the horizontal edges of the slopes converge) and the ribs (the place where the outer side edges of the slopes converge). It is necessary to measure the total length of the indicated roof elements and add 10% for overlaps.
- Internal endova (lower). Placed in the place where the inner side edges of the slopes converge.
- Outer endova (top). Decorative element. Placed on top of the inner one if desired. The total length is equal to the total length of the valleys, plus 10% for overlaps.
- Cornice strip. Covers the ends of the rafters. The element is desirable but optional. Installed along the entire length of the eaves. The total length is equal to the entire perimeter of the eaves.
- End plate. Installed along the entire length of the ends of the slopes. Covers the ends of the battens and protects the tiles from being blown off by the wind. The total length is equal to the length of the corresponding roof elements.
- Waterproofing film. The number is equal to the area of the entire roof, plus 150 mm for each overlap between the rows.
- Special porous self-expanding sealing strip. Closes all gaps between the ridge, valley and the plane of the sheet metal. The quantity should be sufficient for all elements with double-sided installation of the seal.
- Falling bars – their length is equal to the length of the rafters – and the boards for the sheathing should be enough to cover the entire roof with a step of 350 mm.
Here we do not consider insulation and a vapor barrier film – although these are necessary elements, but this has an indirect relationship to the roof.
Installation of metal tiles
In order to make it clear the purpose of certain elements of the roofing system, let’s go from the tasks that need to be solved when arranging the roof:
- Thermal insulation.
- Vapor barrier.
- Manufacturing of lathing with ventilation of the under-roof space.
- Installation of metal tiles.
If it is planned to arrange a residential floor under the roof, then roof insulation is necessary. If the attic is planned to be cold, then you need to take care of high-quality insulation of the interfloor overlap. What happens if there is insufficient thermal insulation? Warm humid air from a living space in winter will condense on the inner cold metal surface, forming water droplets. This moisture will destroy the rafter system, therefore, the service life of the roof will significantly decrease.
The materials that are used for insulation, as a rule, are afraid of water (hydrophobic). When moisture enters them in the form of steam or water, their heat-insulating properties are significantly reduced, therefore, the heat-insulating layer must be protected both from below, from humid warm air with a vapor barrier film, and from above, from roof leaks with a waterproofing film. This is true both for an insulated roof – here the vapor barrier is stretched from the bottom of the insulation, and the waterproofing is on top of the rafters, and for non-insulated – vapor barrier under the insulation of the ceiling of the living room, waterproofing under the sheets of metal tiles.
How to install a vapor barrier. We mount a heat-insulating layer between or under the rafters. We stretch a vapor barrier film under it. Its installation must begin from the bottom, with canvases along the entire length of the room. The next row is made with an overlap of 100–150 mm. The seam is glued with adhesive tape. The film is fastened with a construction stapler to the lower plane of the rafters or to a special crate. Moving up, we reach the ridge, there, without cutting the canvas, we go to the next slope. The vapor barrier film works only in one direction, so when buying in advance, ask which side it needs to be mounted. Insulation and vapor barrier work can be carried out last, after the installation of the roof itself.
Before you is a rafter system without crate. We stretch a waterproofing film along the rafters. Under no circumstances should bitumen-containing materials be used. It is most reasonable to use a universal film – vapor barrier on the one hand, waterproofing on the other. In this case, you do not have to provide a gap of at least 30 mm between the waterproofing film and the insulation. Otherwise, such a gap is required. It is pulled from below in whole strips, with an overlap of at least 150 mm and a sag between the rafters of about 20 mm in the center. The latter must be done to compensate for the thermal expansion of the film itself and possible deformations of the rafter system. The waterproofing layer must extend to the eaves overhangs by at least 200 mm. Along the ridge, to ensure ventilation, it is necessary to make a gap of 200 mm wide.
In order for all the work on the arrangement of the roof to be done more conveniently, it is best to tie them to the waterproofing strips, that is, to pull the first row, make the necessary crate, climb it like a ladder, go to the second row. So until the ridge.
Ventilation of the roof space
Still, the tiles are metal, and if the lower protective layer is damaged due to water, it can corrode. One way or another, there will always be some amount of moisture under the tiles. To prevent it from accumulating there, it is necessary to think over the ventilation of the space under the tiles. The easiest way to do this is by stuffing bars with a section of 25×50 mm along the rafters directly along the waterproofing film – falling bars. Sheathing boards will go along them. If the distance between the upper plane of the thermal insulation and the upper plane of the rafters is at least 30 mm, then when using a universal film, you can do without falling bars. To do this, the waterproofing is stretched, bypassing the rafters from above, and is attached 30 mm below their upper plane with the necessary sag. Thus, the resulting gaps of 30 mm between the insulation and the waterproofing and, if necessary, 25 mm between the waterproofing and the bottom plane of the lathing, will provide sufficient ventilation of the under-roof space..
Installation of lathing
Since, after applying a sheet of metal on top, it is not always easy to get to the right place, it is better to make the crate from an inch board 100 mm wide. We start at the bottom. The first board should be 15–20 mm thicker than the others. Nails with 70–80 mm nails. They must be driven vertically in relation to the ground. From the lower right edge, providing a gable overhang, with a pitch of 350 mm (the wavelength of the tile), boards are packed over the entire roof area. As mentioned, it is better to do this in rows, tied to the width of the waterproofing sheets. Two boards are sewn close to the ridge.
Installation of metal tiles
Before starting the installation of the tiles, it is necessary to fix the inner valleys. You need to start from the bottom. The next element is applied from above with an overlap of 150-200 mm. A porous self-expanding sealing strip is glued along the entire length along the edge. The eaves strip is also fixed before the installation of the tiles.
Now we turn to the metal tile itself. Editing usually starts from the bottom right sheet. For convenience, a board is nailed to the ends of the rafters, protruding upward above the crate by 40-50 mm. The entire first row will rest on it with the lower edge. This will create a perfectly straight edge. After installing the tiles, this board is dismantled. So, the first sheet rises, aligns along the pediment and cornice overhang and is attached with one self-tapping screw to the first right wave from above.
If the slope of the slope is more than 14 °, then the second one from the top (the first wave for overlap). For fasteners, special roofing screws 35 mm with a rubber washer are used. They are screwed in with an 8 mm socket head using a screwdriver.
It is necessary to ensure that the self-cut screws are not wrapped too loosely or too tightly. The place for the self-tapping screw is the lowest (in relation to the sheathing plane) part of the wave. Next, the second sheet rises. Superimposed on the first. In the place of overlap it is fastened with a self-tapping screw. The first sheet is attached completely. In total, about 6-8 self-tapping screws per 1 m are required2. Move on to the next sheet. This may be the third sheet in the bottom row, but the first sheet in the second row is better. This makes it easier to ensure the geometric shape of the ramp is correct. We fix it, go to the 4th – this is the 3rd from the bottom. Etc.
Where the slopes are not rectangular, correct cutting of the sheet is required. For this, a template is used made of 4 boards, fastened at the corners so that the resulting quadrilateral can be deformed freely – the so-called dash:
We put the devil in the right place, fix the shape, transfer the resulting corner to a sheet of metal tile and cut it off. In some places it is more convenient to trim in place. Cutting of sheets is carried out using electric shears, a circular saw or a jigsaw with fine teeth, but in no case using a grinder. It breaks down the top insulation layer, leading to premature corrosion of the tiles..
After the installation of metal sheets, ridge elements are installed. A strip-seal is glued and a ridge is attached on top of it. The porous structure of the seal will not let water through, while providing ventilation. Ridge elements are attached to the ridge and ribs. On the edges, the installation of this element must be carried out from the bottom up. The overlap is 150-200 mm. Fastening is carried out with special ridge self-tapping screws to the sheathing boards.
At the end of the work, the end strips are mounted. They are attached to a pre-nailed end bar. The very last, if necessary, are installed external valleys and snow strips.
Often, when arranging a metal roof, mistakes are made. The most common is the installation of tiles without carrying out all the preliminary necessary work, that is, the tiles are lying, but there is no waterproofing layer and the ventilation gap is not provided. What can be done in this case? First, you can stretch the waterproofing film from below, bypassing the rafters and providing this gap. In this case, it is better to fix it with blocks such as glazing beads along the entire length of the rafters. In this case, however, problems will arise when waterproofing passes through walls. It is not easy to solve them, but it is possible. Another option, when insulating, use moisture-proof materials as the first layer – extruded polystyrene foam, foamed polyethylene (“Teploizol”), etc. This layer will perform two functions – heat and waterproofing. It must also be mounted with a gap of 25-30 mm between its upper plane and the lower plane of the crate.
Thus, the main guarantee of a durable roof is to follow all technological requirements. A properly made roof made of metal tiles will last at least 30 years, pleasing with its appearance.