DIY roof: slate roof

Recommendation points

• Choice of slate
• Installation of lathing
• Roof waterproofing
• Laying slate covering
• Arrangement and protection of junction

Despite the active distribution of the latest roofing materials, slate remains popular due to its ease of installation and low cost. Following our instructions, you can cover the roof with slate on your own or control the quality of work performed by the contractor.

Choice of slate

There are several types of slate: natural slate, polycarbonate, bituminous, but today we will talk about the most popular – wavy asbestos-cement. This roofing material is available in several formats, which differ in size and thickness. Full information on the characteristics of slate and additional parts for slate roofing can be found in GOST 30340-95.

The slate sheet can have six to eight waves. The waveform is defined as a modulus – part of the 40/150 mark, that is, height / width. Of all the formats, the six-column slate is the thickest – 6 and 7.5 mm, the wave has a module of 54/200, the width of the sheet is 1125 mm, that is, one of the waves in the sheet is incomplete covering. The seven- and eight-wave sheets are 5.8 mm thick and 980 mm and 1130 mm wide, respectively. Thus, six and eight wave slates are practically equivalent in terms of format, but the first is almost twice as heavy. The length of the slate produced according to GOST is standard – 1250 mm, but there are also large-format sheets up to 2.5 m long.

The overwhelming majority of slate is produced in the form of untreated sheets, with which the main disadvantage of this coating is associated – fouling with moss and darkening due to the accumulation of dust in the pores. Painted slate does not have such a flaw, but it is somewhat more expensive. However, the protective coating can be applied independently: clean the slate with a metal brush, dust it off and open it with PF-020 or PF-010M pentaphthalic primer. If you want to give the coating a color, the second layer is applied to the universal alkyd enamel PF-115. The protective coating on slate performs not only an aesthetic function, but also increases the hydrophobicity and service life of the roof.

Installation of lathing

Roofs of completely different configurations can be covered with slate – from ordinary gable to hip, including those with internal convergence of slopes. At the same time, the supporting system is traditionally formed by rafter legs, to which a horizontal crate is nailed for attaching slate sheets.

For the lathing, you can even use an unedged board, but always of the same thickness – at least 25 mm, the permissible width is from 100 mm. The lathing step is determined by the length of the sheets used. The first bottom board is nailed flush with the bottom edge of the rafter leg. All subsequent ones so that each slate sheet is fastened along three lines: 100–150 mm from the lower and upper edges, as well as in the middle. Thus, taking into account the slate overhang of 50-100 mm above the rafter legs, the first two boards are placed with an axial distance of about 40 cm, the rest – 50 cm each. In this case, the third board should be positioned so that the sheet protrudes about 50 mm above it. When the main elements of the crate, to which the slate will be fastened, are nailed, the gaps between them are filled with second-rate sawn timber, which serves as a support for the slate for a more even distribution of loads.

Fastening the crate to the rafters should not be done with self-tapping screws; it is much more correct to use nails from 100 mm for this purpose, even better if the nails are rough. The slate is very sensitive to the curvature of the lathing, therefore, before the final fixing, it will not be superfluous to pull the cord and align the boards in a common plane, placing wooden chips or shreds of roofing material under them. On the lines of convergence of the slopes, where the skates will later be arranged, it is necessary to nail the embedded boards for attaching the protective linings.

Roof waterproofing

Slate roofing requires a mandatory waterproofing device to protect against leaks when the snow cover melts or in case of destruction of the coating. This part of the roof can have two realizations, depending on the presence of insulation.

For non-insulated roofs, it is customary to use roofing material, euroruberoid or glass insulation in one layer. Installation of waterproofing is carried out horizontally from bottom to top. Each canvas is attached to the crate with special buttons, which are called roofing buttons. The upper canvases cover the lower ones with an overlap of 100–120 mm, while the fold is warmed up and pressed to form a tight sealed joint. On skates, the waterproofing is trimmed along the line of convergence of the slopes, then one solid sheet is laid on top, which is also soldered to the underlying layer. In the same way, the waterproofing circuit is closed in the valleys..

If a protection belt in the form of mineral wool is placed in the rafter system, waterproofing is carried out with superdiffusion membranes. The order of their installation is similar to “cold” waterproofing with the only difference that the overlap is performed according to special markings on the edge of the roll material. In addition, sealing between the canvases is not performed, the waterproofing is attached only in the upper part, then the fasteners are covered with a top layer. A prerequisite for laying superdiffusion membranes is their correct orientation: the side on which the fleecy cover is present must be facing up.

Laying slate covering

Installation of slate can be done in two ways. On slopes, in which the width is much greater than the height, the sheets are laid apart with an offset of 2-4 waves relative to the previous row. This arrangement helps to avoid the formation of four layers of slate at the cross joints, which occurs when laying without displacement..

Nevertheless, direct placement of sheets also has the right to life, this method is optimal for covering high slopes of small width. In this case, before installing an adjacent sheet in a row, it is necessary to trim the corner on the bottom sheet to the width of the covering wave and the height of the overlap between the rows. They act in the same way when installing the upper row: the corner of the lower sheet is cut in the opposite direction, due to which there are no areas with a four-layer overlap in the coating.

The first row of slate is aligned horizontally, for which the mooring cord is pulled along the bottom line. Each sheet has nine attachment points, three in each line. The extreme points should be located no closer than the second wave from the edge of the sheet. The slate is fastened with special nails, the head of which is protected by an aluminum or plastic cover. The nail is set at the highest point of the wave, then the slate is broken through with one sharp blow and the nail is hammered into the crate until the head is firmly pressed against the coating. From the seamy side, the nails cannot be bent, but they can be cut with a grinder, leaving “hemp” 5-7 mm.

Installation of a slate roof is a hazardous job, the height factor is aggravated by the significant weight of the materials. Therefore, work must be carried out necessarily with a safety cable, which is thrown over the roof and tied to a fixed object on the back of the building. It is most convenient to lift the slate to the roof along two parallel pipes as along guides, picking up the sheet from below with a hook on a rope. A not entirely obvious hazard factor is the dust generated during cutting, so the slate should be processed only with a respirator and goggles. It is the asbestos dust generated during cutting that causes the notorious danger of asbestos-cement slate, when the coating is fixed on the roof, it is absolutely harmless.

Arrangement and protection of junction

Some difficulty is the flattening of the coverage on the lines of convergence of the slopes – skates and valleys. The upper ridge is trimmed quite simply: a horizontal cord is pulled along which a cutting line is applied to the slate at the fitting site. You can do this on inclined skates, it is only important to calculate the height of the coating above the waterproofing in advance. One of the sides of the abutment in such cases is cut along the cord, the opposite is marked with a pencil from the back side along the profile of the already laid coating.

In the valleys, it is not possible to try on the slate locally, therefore, proceed as follows:

1. An overlap line is marked on the extreme solid sheet;
2. From the marking, the distance to the center of the valley is measured in the lower and upper parts.
3. The obtained values ​​are transferred to a sheet of slate and cut diagonally, making an indent of 20-30 mm.

GOST 30340–95 provides for the manufacture of special products made of asbestos cement for the protection of abutments: the lower and covering elements of the ridge, tray parts for valleys and corner strips to protect wind overhangs. However, these products are extremely rare, therefore, the ridge and valleys of slate roofs are covered with protective elements made of roofing iron with a galvanized or polymer coating, and the wind overhangs are sewn up with boxes of boards.