How to install slate roof tiles?

There are 2 methods for installing slate roof tiles: gluing with adhesive and fastening with nails, both using a pre-installed underlay. Apart from this, a waterproofing membrane is always necessary. The differences between the two methods consist in water’s ability to penetrate (less when using adhesive) and durability of fastening tiles with nails (more solid this way). Therefore, based on your project’s particularity and tile size, one of these 2 methods will be selected.

photo source: sigroofing.co.uk

A. Fastening with nails (copper, with large head) includes the next steps:

1. run a trial installation, for deciding tiles lay out

2. use a special hammer (not the carpentry hammer but a hammer fitted with sharp beak for drilling) for the 2 holes of each tile

3. use a thin wooden plank as support at the edge of the roof; it will function as spacer and will prevent water dripping on the wall

4. install the first row of horizontal tiles, leaving approximately 2 cm on the side (on the 30 cm side) and about 4 cm on the 15 cm side. For tiles with size of 30 x 60 cm, 25 x 50 cm, 20 x 40 cm and 5 -7 mm thickness you need to coordinate these dimensions. For the 30 cm tile width we leave 3 cm on the side and 5-6 cm respectively on the 60 cm side. If the first row is installed vertically, then leave about 5 cm. Usually, binding is done in two nails, battered up to the tile level, without pressing it and making sure nail’s head covers entirely the hole. Nail’s head should not press the tile because it might crack, yet space you should not allow water penetration

5. install the next row vertically over the first row. Cut a slate tile (with special scissors) and fasten it to the end of the second row so that the contact areas between the tiles of the second row do not overlap the ones from the first row. This method of fastening tiles will not allow water penetration. The second row is installed like this over the first row

6. the third row is installed over the second, approximately 7 cm distance from the base of second row and aligned so that the contact between two tiles in third row does not overlap the contact from the second row. As a result, in the edge area there are 3 layers of slate preventing water penetration

7. proceed further

8. in the upper side of the slope, in the valley area, install tiles considering the context (water collection or not) and the customer preference.

photo source: renaissanceroofing.com

B. Gluing with adhesives includes the next steps:

1. measuring the surface with a tape measure or carpentry tool. This time, we are not supposed to cut tiles, because it should exceed the roof size at the edge, thus preventing water dripping on the wall.

2. running a trial installation. It is recommended to open packages and observe the color difference, the result of selections from the same type of stone. Tiles will be laid out in the preferred color variation.

3. check compliance with installing conditions: dry tiles (protected from moisture at least 24 hours before installation), installation temperature of 5 - 25 °C, normal humidity (avoid installation during days with high humidity)

4. choose the type of adhesive required (natural stone adhesive)

5. you can waterproof tiles before installation (with professional sealing solutions). After cleaning the tiles, spray the waterproofing solution over the surface by proceeding according to manufacturer’s prescriptions. Waterproofing can also be done after installation, however this implies more severe conditions.

6. after choosing the adhesive and preparing it according to the manufacturer's instructions, begin the installation. Slate tiles with low absorption are installed by direct application.

7. spread the adhesive on the surface considering its drying time, to avoid drying before installation. Adhesive can be applied over the surface or you can also apply it over the tile (for superior adherence). Installations in areas with increased humidity require an adhesive tile coating of minimum 60% (roofing slate). Apply adhesive by “brushing” and stay away from other methods of applying adhesive, since it is necessary to ensure the perfect adherence. We apply the adhesive on a rectilinear direction without making curves with the trowel. The result is a string of tiny, parallel tracks, serving as support for the tile. Apply adhesive so that grooves remain perpendicular to tile’s width. All these operations are aimed at increasing adhesion.

8. begin installation from an edge for ensuring correct tiles lay out. Lay tiles directly over the surface and push them gently, possibly moving it gently back and forth without rotating it. 

9. install without joints. In the end, clean excess adhesive with a damp sponge.

10. allow 12 – 24 hours for surface drying, depending on context, or observe manufacturer’s instructions.