Whether you choose western red cedar shingles or oak shiplap board, wood brings a natural sense of style
Natural and sustainable, wood is a cladding material that is simple to use and easy to find – it does grow on trees after all! Although us Brits haven’t traditionally embraced wood cladding in the way the Americans or Scandinavians have, there’s no reason why it shouldn’t work well in our comparatively milder climate.
Timber is diverse in type, and many different effects can be achieved by varying the species of tree, type of board and finish. Wood can look natural enough to blend with surrounding trees, or create an off-the-wall facade with bright colours and fantastic shapes and patterns.
Many types of wood are suitable for external cladding. Hardwoods like oak, sweet chestnut and iroko are the most expensive. Then come mid-priced durable softwoods like cedar, fir or larch, though the current popularity of western red cedar has driven up its price even higher than that of oak. When treated, you can even use cheap softwoods like pine or spruce.
Boards work vertically, horizontally, even diagonally. They can overlap, or sit flush. The width can be varied to create large expanses of wood or get a stripe effect with narrow profiles. You could opt for shingles or shakes – small, tile-shaped wood sections split or sawn down the grain that give a textured effect – but do factor in the extra cost as they are labour intensive to install.
Wood cladding, like any other, is attached onto battens that leave a ventilated cavity behind. Don’t leave more than 60cm between battens, otherwise there is a risk your cladding may twist or distort. All timber cladding will allow some leakage, so make sure you fix a weatherproof breathable membrane behind the battens. And moisture is a big issue with timber cladding – wood will always change dimension slightly due to seasonal changes of humidity, and the cladding must be fixed to allow for this by leaving sufficient overlaps, or gaps between flush jointed boards.
Patrick Hislop of the Timber Research and Development Association (TRADA) says: ‘To allow this movement more easily don’t plan to use boards of more than 150mm, and above 100mm use two fixings per batten to hold the board flat. Try to install cladding at its typical moisture level (13-19 per cent) so that movement is minimised, and ensure you leave openings at the top and bottom of cladding to allow air to enter.’ Nails or screws should be stainless steel as this will avoid corrosion in the long term. Ring shank nails have enough give to take up any movement around the fixings in softwood, but hardwood boards are usually screwed, so remember to leave pre-drilled clearance holes.
Naked wood Hardwoods and some softwoods such as western red cedar, Douglas fir or larch can be left unfinished to bleach to a natural grey, or treated so they remain their original, more intense shade.
Colour Woods can be stained with natural wood colour, or painted any shade you choose. ‘At least one coat should be applied before cladding is erected,’ says Patrick. ‘This gives a good base for the final coat and avoids cracks if the boards shrink. Modern finishes can last up to eight years without repainting, but redecorate before any grey wood becomes visible, otherwise the new finish won’t adhere properly and last as long.’
Preserving treatments are only really necessary for cheaper woods. These can be pressure vacuum treated with a boron-based preservative – far less toxic to the environment than the old arsenic formulations. If your home is close to trees or very affected by traffic pollution, coating wood rather than leaving it to bleach lessens the risk of staining or blackening.
Oak, ash; alder; beech, birch; chestnut; elm; iroko; maple.
Pine; cedar; spruce; fir; larch.
Words: Joanna Booth