Also know as Yakisugi; translates to ‘burnt cedar board’ which is an age old Japanese protective wood treatment. A typical timber cladding board is literally charred on one side which creates a carbon layer on the surface of the timber. This forms a protective layer to combat UV, weather decay and insects in lieu of a coating while also providing a very striking appearance. The board is brushed to remove any of the loose heavy charcoal that may come away leaving subtle textures and a blackened surface.
Timber has very interesting properties in that it has a char factor that will protect the integrity of a timber from structural failure under certain conditions. This performance is better than structural steel as steel will quickly bend and fail under high heat. All this is a moot point in severe fire conditions as fire will take out anything and everything.
One of my favourite stories about the benefits of solid timber floors versus engineered / laminated timbers relates to the royals and charred timber. Some may recall when St George’s Hall in Windsor Castle erupted in flames in 1992 severely damaging approximately 100 rooms. Many rooms were emptied during the fire and also major art works happened to be loaned out to traveling exhibitions at the time. The roof was fully engulfed and the burnt roof beams then fell to the floor and only burnt the top layer of the very thick timber floor boards. The building was cleared of all the rubble however the charred floors were mostly still in place, damaged but in place. The artisan builders then set about lifting the boards, sanding them down to remove the char and turning them over to live on into the future for many years to come. The repair bill was approximately £37 million and this prompted the Queen to begin paying income tax and also set about Buckingham Palace opening to the public to help pay for the restorations.
Thanks to Warwick Mihaly and Architeam for putting on a great lecture on Building Skins and specifically Hurford’s Timber for providing information on the Shuo Sugi Ban, very interesting stuff.