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End Grain of Exterior Timbers

The end grain of timber absorbs moisture at a much higher rate than the face or edges – here’s what you need to do to prevent wicking and unsightly stains.

The end grain of timber absorbs moisture at a much higher rate than the face or edges - imagine a straw and you start to get the idea.

In exterior applications where water is present, incorrect installation or detailing can cause ‘wicking’ of moisture up the end grain and can lead to unsightly staining, mould growth and possible early onset of fungal decay.

The ‘wicking’ effect can be further exacerbated if an inadequate gap is left between the timber end grain and adjacent materials such as flashings.

Failure to leave an adequate gap can also lead to capillary action that pushes water in up in behind the wall or window system.

For this reason Abodo recommends to seal the end grain of exterior timbers in order to restrict the movement of water into the timber end grain. This can be done with two coats of Protector, paint or other specialist wax based end grain sealers.

We also recommend cladding to have a minimum of 5mm gap from base of cladding to flashings and flashings must have a minimum 5 degree fall to shed water away from the wall.

Application of a 5 degree mitre cut to board ends at base of cladding is also good practice in order to form a drip edge, further reducing water ingress. For decking we recommend a 2mm gap at butt ends to allow end grain to dry out in service.

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