Choose a product for internal roof insulation
Stone wool comes in different slabs and rolls. A product intended for a façade or flat roof is not automatically the right choice between rafters. ROCKWOOL Rockroof Flexi is one example of a flexible product for pitched roofs. Available depth, support and junction details guide the specification.
Moisture control and airtightness are separate tasks
The wool does not replace a weather-resisting underlay or an airtight internal layer. Check existing membranes and repair leaks before closing the construction. Detail the selected vapour-control layer continuously around timbers and windows using compatible tapes and seals. Assess unusual existing build-ups before installation.
Compare the complete construction
Rd describes the selected insulation layer; Rc relates to the complete roof construction. Timber content and junctions affect the result. For acoustic and fire performance, request a documented build-up including the internal lining. More mass or a higher material price alone does not prove a better roof.
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Technical sources
Checked on 23 September 2026.