Getting the fixing specification wrong on a natural slate roof is an expensive mistake. Use the wrong fixing for the exposure zone, or specify a nail gauge that is too light for the slate weight and roof pitch, and you are looking at callbacks, uplifted slates and a warranty problem. CUPA PIZARRAS, one of the largest natural slate producers globally, has launched an online fixing specification tool to take the guesswork out of the process.
What the tool does
The online tool, available through the CUPA PIZARRAS website, guides architects, specifiers and roofing contractors through the key variables that determine fixing specification: roof pitch, slate dimensions, local wind exposure classification and the substrate being fixed to. The output is a fixing recommendation that matches the input parameters.
This replaces manual calculation or having to call a technical rep for straightforward specification queries. For specifiers working on multiple projects, or contractors pricing jobs in different exposure zones, it removes a friction point in the process.
Why fixing specification matters for natural slate
Natural slate is a heavy material. A standard Welsh or Spanish slate at 500mm x 250mm x 6mm weighs approximately 14 to 16 kilograms per square metre when laid. At high exposure locations on the coast or at elevation, wind uplift forces on individual slates can be considerable. The fixing holds the slate against those forces.
The wrong nail gauge, an inadequate number of fixings, or fixings corroding prematurely due to material incompatibility can allow slates to lift or shed. For a high-pitched roof in an exposed Welsh or Scottish coastal location, that becomes a safety and structural issue, not just a cosmetic one.
CUPA PIZARRAS's specification tool takes local exposure into account, which is the variable most commonly overlooked when contractors replicate a specification from one site to another without adjusting for location.
Who it is for
Roofing contractors, architects and specifiers working with natural slate, and merchant technical staff who assist on specification queries. The tool is free to use.