Insulation Slabs

Slab insulation is a semi-rigid mineral wool panel that holds its shape for a cleaner, more consistent fit in studwork, cavities, and between joists/rafters. Insulation rolls are flexible and better for fast coverage across larger areas where long lengths can be cut and laid. Choose slabs when you want a defined thickness and stability in vertical or framed sections, and rolls when speed and continuous coverage are the priority.

Choose slab insulation thickness to match the depth of the space you’re filling (stud, joist, or rafter depth) and the performance target in your build-up. Common options like 50mm, 75mm, 100mm and 150mm are used depending on frame depth and whether thermal performance or sound control is the priority. If you’re layering insulation, calculate thickness per layer and avoid compressing mineral wool, as this can reduce performance.

Measure the total area to insulate in m², then divide by the pack coverage (m² per pack) shown on the product page and round up to whole packs. Add around 5–10% for cuts and offcuts, especially around perimeter edges, openings, and services. If you’re insulating different zones or using multiple thicknesses, calculate each section separately to reduce waste.

Yes - mark the size and cut slab insulation on a flat surface using an insulation knife or a long serrated blade for a clean edge. For a secure friction-fit, cut the slab slightly oversize (typically 5–10mm) so it sits snugly without gaps and supports itself in the bay. Avoid over-compressing the slab or leaving voids around cables and pipes - neat trimming gives more consistent performance.

Many mineral wool insulation slabs are available with non-combustible fire ratings, but it depends on the specific product and certification. Check the product listing or datasheet for the stated fire classification (e.g., A1/A2 where specified) and any system limitations. If a project spec calls for a particular rating, choose slabs that explicitly state compliance rather than assuming.