Celotex Isover

Insulation for Masonry Overcladding

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These types of wall typically comprise an outer skin of masonry and an inner skin of lightweight steel frame (SFS) construction, although depending on building height the inner skin can also be of timber-framed or cross-laminated timber (CLT) construction. The SFS is typically filled with a mineral wool roll or slab (ISOVER Steel Frame Infill Batt can be considered), then finished internally with plasterboard and externally with a sheathing board to provide protection from the elements. Additionally, membranes such as a Vapour Control Layer (VCL), Air and Vapour Control Layer (AVCL) or a breather membrane may also be specified.

The insulation between the SFS alone is usually not enough to comply with Building Regulation thermal requirements, so additional insulation can be installed against the sheathing board and fixed in place with a brick channel & tie restraint system. The sheathing insulation is typically a stone mineral wool slab, such as ISOVER Polterm Max Plus. Between the outer face of the sheathing insulation and the masonry outer leaf, a minimum 50mm residual cavity is maintained.

Key Considerations

When using Celotex or ISOVER products, you need to satisfy yourself that use of the product meets all relevant national Building Regulations and guidance as well as local, national and other applicable standards relevant for your construction or application, including requirements in relation to fire and applicable height restrictions. In addition to the product datasheet, please refer to the following product documents:

Celotex products should not be used in the external walls of buildings over 18 metres in height (England and Wales) or 11 metres in height (Scotland). Recent changes to Building Regulations mean that only non-combustible insulation or insulation of limited combustibility can be used in buildings of that height.

The building detail is for illustrative purposes only. It does not constitute advice and should not be relied upon.


Insulation products
Product Name Thickness Range Sizes Lambda
ISOVER Polterm Max Plus 50-200mm Width 600mm, Length 1200mm 0.035 W/m.K
ISOVER Steel Frame Infill Batt 50-100mm Width 600mm, Length 1200mm 0.036 W/m.K