The ISS-10 Prime is quarried in North Western Spain in the Orense region. This traditional Spanish slate is very hard and durable with a very low water absorption rate.
It has a Mid Grey colour and boasts a clean flat surface with neatly dressed edges. This roofing slate is flat and even, meaning there is minimal sorting and grading required resulting in less time and work for tradesmen.
The ISS-10 Prime is available in a 5mm thickness.
Prime Grade slates are of a high quality and good selection, they will require slightly more sorting and grading prior to fixing than the Ultra-Grade, but once done Prime-Grade slates offer a cost-effective solution that will still achieve a flat, uniform appearance on the roof.
Test results: The ISS-10 slate boasts a W-1, T-1, S-1 rating, meaning it conforms and surpasses all the top UK tests for water absorption, thermal cycle resistance and sulphur dioxide exposure.