Timber Decking Roof

The timber used for decking in these applications needs to be substantial, especially as they have to be heavy enough to provide protection to the underlying Sika Plan waterproofing and also a degree of resistance to wind uplift forces. It is important that the gaps between the individual planks are no greater than 4mm, this helps to prevent lighted cigarette ends from finding their way through and also to exclude UV radiation from reaching the membrane.

Generally, ballasted membranes are loose laid and only restrained against wind uplift forces by the dead weight of that ballast.
Substantial timber decking as described above will probably be dense enough, relative to its surface area, to stay in place in all but the more extreme wind conditions. However, the negative wind loads acting on the surface of the decking will be transferred through the gaps and start acting on the greater surface area of the underlying membrane. If the wind forces are high enough they can start to lift
the membrane that will then act like a sail under the decking and possibly cause it to be lifted out exposing the roof structure.

Suitable separation layers for use between the SGmA and the decking are the Sika Plan S-Felt Type T 300g/m2 polyester fleece or the SBV protective layer.

The only separation layer suitable for use between the SGmA and the decking is the Sika Plan S-Felt Type T 300g/m2 polyester fleece as it is air permeable. Any layer that was not permeable, such as the SBV, would act as a sail behind the decking.

Any preservative treatment process used on the timber should be of the waterborne salts type rather solvent based one, which are
detrimental to the membranes.