Wincilate Slate is eminently suitable for use as window cills owing to the fact that it is chemically inert, non-porous, does not warp, shrink or rot and may be fabricated in slim profiles. It also provides a cill and window-board in one piece if required and so reduces fixing costs. Maintenance costs are also reduced drastically as the need for painting or replacement is eliminated.
Two main types of cills are fabricated flate and weathered. Each type is available to suit various wall thicknesses and should have a minimum overhang on the front edge of 45mm. Cills can be supplied with a drip groove as well as a water bar groove if required.
Weathered cills are supplied in 25mm minimum thickness and the external edge should not be less than 19mm thick. Flat cills and windowboard are supplied to a minimum thickness of 19mm. Intermediate thicknesses up to 75mm are readily available. Lengths up to 2m may be supplied although cills are more readily available in sizes up to 1.5m. An allowance is normally made at ends of openings for jointing, and intermediate lengths are but jointed with an allowance for pointing as required with approved black polysulphide mastic on installation.
Slate cills should be stored in an area and in a manner that will keep them in prime condition; they should be handled with respect and must be carried to the fixing point. “Walking” the cills on their ends will result in damage and impair the final appearance. Cills are laid on a mortar bed of approximately 12mm and gently tamped into position ensuring a straight and level line together with the correct overhang dimension. The designed fall or weathering must be maintained and, if mastic pointing is required, joints should be raked back and cleaned to the depth of slate before mortar sets. Immediately after fixing remove any surplus mortar and debris from surfaces, ensuring that throating is clear on underside. Finally, all surfaces should be wiped over with a clean, damp sponge to remove any traces of cement or plaster that may remain. Protect cills from any possible damage by following trades.
Cills are supplied in their natural blue-grey colour and are rubbed smooth on exposed face and edges.
When specifying remember to ask for:- Wincilate “Best Quality Welsh Slate Cills”