Monday 20 May 2024  

Pitched roof with timber construction

The most effective thermal insulation on pitched roofs can be achieved by using a combination of insulation materials, which are selected according to the given requirements.

Pitched roof is insulated between roof construction elements (purlins, rafters, ties…) with flexible thermal insulation, e.g. mineral wool. Fibre insulation adapts perfectly to the rigid roof construction, thus eliminating the forming of additional thermal bridges.

For additional insulation above or below rafters we can select among wool, cork or polystyrene board insulation. When insulating with wool, an additional load-bearing construction should be made on the inside and on the outside of the existing roof construction. Only when using (compact) stone wool with high compressive strength as additional insulation above the rafters, the additional construction is not required. By installing FIBRANxps insulation the cost of additional construction is eliminated.

Internal pitch roof insulation
The attic as a living space is additionally thermally insulated with FIBRANxps ETICS GF or BT  boards, on the inside of the roof. The surface of the installed ETICS boards is then rendered with ETICS façade system (brochure on facades), but instead of the finishing façade layers the indoor render is applied, or levelling putty, if smooth ceiling surface is desired.
In this case, or when installing combined insulation materials, vapour barrier is not required, but a vapour permeable secondary roofing is installed on the external side of the thermal insulation.

The rendered indoor insulation FIBRANxps ETICS GF or BT serves at the same time as the finishing timber or plasterboard cladding. Such a solution is suitable for new buildings, as well as for refurbishments or remedial work of attic ceilings.

External pitched roof insulation
The long thermal insulation boards FIBRANxps MAESTRO are fixed directly on rafters or on timber-board roof surface, together with the secondary roofing and tiling battens that provide ventilation of the roof. Due to the possible damage of roof tiles and penetration of rainwater through joints between roof tiles in windy weather, it is recommended to install diffusion open water resistant membrane as a secondary roofing.

Thermal insulation boards FIBRANxps MAESTRO are manufactured with the tongue-and-groove (D) edges for easier installation. As tongue-and-groove design prevents the forming of thermal bridges, the installation of a single layer of boards is sufficient.

Due to the exceptional load-bearing capacity of the insulation boards, the additional load-bearing roof construction is not required. The same principles apply for the thermally insulated pitched roof with visible rafters.


In case of combined insulation with wool insulation materials, water vapour permeability of the entire construction should be balanced by applying vapour retardants or vapour barriers. Typical solutions are shown in technical designs.

- Roof tiles glued onto insulation

Roof tiles can be glued directly on thermal insulation boards FIBRANxps 300 CT. Channelled (grooved) surface gives the insulation boards excellent adhesive properties. Adhesive mortar or PU adhesive foam is applied in intermittent strips in order to provide continuous ventilation under the tiles. Roof ventilation is recommended in order to avoid overheating of the roof, and in this way to prevent condensation forming under the roof tiles, which would affect the durability of the roofing.

In this case the roof tile underlay (waterproofing) is applied directly on the wooden-board roof construction.


In case of combination with wool insulation materials, a balanced water vapour permeability of the entire construction has to be provided, with vapour retardants, or vapour barriers. The individual solutions are shown in technical designs.

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