Timber charring

With a small time window before we start the assembly of the frame and a sunny weekend to bag, it’s been the perfect opportunity to do some ‘Shou sugi ban’ aka timber charring. We have air dried locally grown Western Red Cedar cladding in one of the sheds for the past four months, with the moisture levels dropped nicely from the original 30-40 odd to a more suitable 20-25%.

Timber charring is a way of preserving cedar, it helps protect the timber cladding against fungi and insects, it enhances fire-resisting properties and last but not least, makes the cladding beautifully textural.

The traditional Japanese technique involves creating triangular ‘chimneys’ of cedar planks and burning the inside face over a small fire. The stack effect draws the fire in and flames rapidly spread upward. I have tried this technique, but had variable results in terms of consistency of char. It is rather difficult to control the degree of burn with 3.6m long planks.

I have also tried another technique, this time using a propane blowtorch, where a rectangular box is created and torch is fired inside. This produced some spectacular burn (ses photo below), but again the control of char was quite limited and some of the edges had to be finished off separately.

Finally, I resorted to a fairly standard blowtorch technique, laying several planks at any one time to make the most of the flame. Low moisture content of the cladding meant a really clean burn, with sweet smell of cedar filing the air.

I’ve tried couple of options finishing the charred cladding – soft brushing & staining with OSMO black oil woodstain, and just oiling with OSMO UV oil with no brushing. Both options produce a beautiful finish, but the brushed version is a lot more time consuming (and dirty!). Having looked at the design of the house, I’ve decided to limit the brushed finish cladding to the covered verandah, where the cladding will be in most contact with us. ‘The Gator’ effect cladding (without the brushing) will cover the rest of the house.

Timber charring