- What minimum roof pitch is required in order to utilize slate?
- What roof decking is required for the application of slate?
- What weights should be taken into account when considering natural slate?
- What climatic restrictions apply to the use of natural slate?
- Can you suggest a competent slate roofing contractor who can supply the slate and install my roof?
- How long can I expect a slate roof to last?
With special consideration for slate size, headlap and underlayment – natural roofing slate can be applied to roofs with a slope of four inches per foot.
One inch board sheathing or 3/4″ APA plywood provides a suitable deck material for the installation of natural slate. This material provides minimum deflection during nailing, supports the weight of the slate between rafters and provides adequate resistance to nail pull out.
The weight of nominal 3/16″ slate is 7 – 8 lbs. per square foot and nominal 1/4″ is 9 – 10 lbs. It is worth noting that the common practice of applying 3 layers of asphalt shingles, before tearing off, creates a combined total weight of 7+ lbs. As with the application of any roofing material, dead load weights for natural roofing slate should be taken into consideration at the design stage or prior to re-roofing.
Good quality natural roofing slate has been used under the harshest climatic conditions in the world and has proven performance dating back a thousand years. Poor quality roofing slate yields a limited life expectancy under moderate conditions and therefor its use should be restricted to milder climates with very careful evaluation of precipitation and freeze thaw cycles.
We maintain a database of qualified North American roofing contractors who have the necessary skills and experience to install your roof. With some basic information regarding your roofing requirements, we can recommend the contractors that are most capable and interested in your type of project.
The life expectancy of a slate roof will depend on climatic conditions, roof pitch and slate quality. Climatic conditions and roof pitch are variable, however, ASTM International’s C406 Standard Specification for Roofing Slate establishes expected service life for grades of slate as S1 over 75 years, S2 40-75 years and S3 20-40 years..