Terrawool Soffit Slab is manufactured using non-combustible stone wool insulation. Available with a plain, foil or tissue facing which can provide up to 4 hours fire protection to the underside of concrete soffits.


Suitable for use with concrete soffits where a thermal, fire or acoustic performance is required.

Fire performance

Soffit Slabs have been tested to BS EN 1363-1 to offer fire protection to reinforced concrete soffits. When applied to the soffit using the recommended fixings and pattern, 130 and 140mm thick products, with and without facings, provide 3 hours fire insulation and integrity to a minimum 90mm thick floor slab. 150 and 160mm thicknesses provide 4 hours to a minimum 150mm thick slab.

Thermal performance

Terrawool Soffit Slab has a thermal conductivity (k value) of 0.034 W/mK.

Thermal resistance of un-faced Soffit Slab:

  • 130mm Soffit Slab: 3.82 m²K/W
  • 145mm Soffit Slab: 4.26 m²K/W
  • 160mm Soffit Slab: 4.70 m²K/W

A typical construction comprising of a 150mm concrete floor slab underlined with 130mm thick Soffit Slab would achieve a U-value of 0.25W/m2K. A U-value of 0.20 W/m2K can be achieved using 160mm thick Soffit Slab.

Technical information

Terrawool Soffit Slab achieves a reaction to fire classification of A1 – BS EN 13501-1.


Terrawool Soffit Slabs are chemically inert and compatible with most materials with which they are likely to come into contact in normal building applications