supporting substrate

The sub-structure framework is to be designed and executed according to structural requirements (related to building and location).

Before starting work, coordinate the dimensioning and execution of the sub-structure framework, ventilation cavity heights, as well as the detailing of connections and terminations (e.g. eaves, hip or ridge details) with the designer and carpenter.

PREFA roof products are to be installed on a fully supported substrate. Requirements from national standards and regulations must be taken into account!

Fully boarded substrate

Irrespective of national standards and regulations, the framework conditions (“minimum requirements”) for installation on a full formwork are defined by PREFA as follows:

Board width: 80–160 mm
Board thickness: min. 24 mm (min. 22 mm when dry)
Wood humidity: max. 20%

Sheets made of wood-based materials

Irrespective of national standards and regulations, the framework conditions (“minimum requirements”) for installation on wood-based sheets are defined by PREFA as follows:

Thickness of wood-based sheets: min. 22 mm*
When using wood-based sheets, a separation layer is required.

*In case of a different (lower) sheet thickness, the thickness, the selection of the fastener as well as the structural suitability of the sub-structure framework must be coordinated with the manufacturer of the wood-based sheets.

OSB sheets as a substrate are special purpose solutions and should be planned as such.

Note

PREFA does not recommend the use of OSB sheets as a sub-structure framework for metal roofing with or without a separation layer.

Supporting substrate

Substrate