Installing a slate roof is challenging but provides an aesthetic quality that can last for 150 years or longer. Although slate roofs come in a variety of shapes and sizes, installation is faster and less problematic with larger-sized tiles and may be more suited to a "do-it-yourself" project. Slate is suitable for roofs with a minimum slope of 4 inches of height per 12 inches of length and requires a 3-inch headlap to ensure water tightness. Fitting a slate roof requires the correct preparation and application techniques to complete the project effectively.
Install a minimum 3/4-inch roofing grade solid lumber deck, rather than standard plywood or OSB decking, to ensure the longevity of the roof and avoid the need for deck replacement during the life of the slate. Sweep the deck of loose debris with a push broom.
Lay 13.6kg roofing felt over the entire roof deck. Fasten a cant strip along the eave edge on top of the roof deck using a nail gun and stainless steel roofing nails to provide the correct starting angle for the slates.
Position the first starter course slate upside down, and turned 32.2 degrees Crom its normal installation position, so its length is parallel to the eave edge. Overhang the eave edge by 1 1/2-inches and the rake edge by 1-inch. Fasten the first slate into position through the pre-drilled holes with stainless steel roofing nails and a slate hammer.
Position the next starter course slate adjacent to the first and butt the two edges together. Fasten the slate into position using the same method as explained in Step 3. Continue to fasten the starter course along the eave edge to the far rake edge.
Position a slate over the starter course at the eave and rake edges so that the bevelled slate edges line up and the slate width is parallel to the eave edge. Fasten through the pre-drilled holes so that the nail head rests in the countersunk hole. Continue to install the rest of the first course of slates in the same way across the roof and over the starter course.
Determine the exposure surface of the slate courses by subtracting a 3-inch headlap from the length of the slate and dividing the remaining number by two. The 3-inch headlap is the measurement of one slate's overlap over the slate that is two courses below it,. It is critical to maintain a 3-inch headlap to prevent water penetration.
Using the exposure measurement calculated in Step 6, measure from the top of the first course of slate, and snap a chalk line across the roof for the second course of slate. Snap chalk lines across the roof at the subsequent slate exposure measurements up the roof for each corresponding course of slate.
Position the second course of tiles using the chalk line and stagger the course by half a slate width from the first course. Use a slate cutter to cut a tile along its length to adjust a slate to fit at the rake edges of the roof. Fasten each slate using the same method as explained in Step 5 using stainless steel roofing nails and a slate hammer..
Stagger each course by half a slate width from the preceding course and use the exposure measurement chalk lines to accurately position the slates to maintain the 3-inch headlap. Position and fasten the slates using the same method as you did previously until the roof is complete.
Use scaffolding around steep roofs to prevent injury from falling.
Tips and warnings
- Use scaffolding around steep roofs to prevent injury from falling.