Natural and Sustainable, wood is a cladding material that is simple to use and easy to find – it does after all, grow on trees after all!!
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 coloursand fantastic shapes and patterns.
Wood Type
- 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 price even higher than that of oak in some cases. When correctly treated, you can even use cheap softwoods like pine or spruce.
Cladding Type
- 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 stipe effect with narrow profiles. Complexity of design and width of timber profile will always be significant factor in terms of the cladding cost. As a general rule, complexity of design and small widths of timber increase labour installation costs. Large widths of timber can increase cost due to availability / size of trees available for procurement.
Fixing / Installation
- Wood Cladding, is best fixed onto timber battens leaving a suitable ventilated cavity behind. We recommend not leaving much more than 600mm gap between battens, otherwise there is a risk of the cladding twisting or distorting;
- All timber cladding will allow some leakage from the elements and for this reason a weatherproof bearable membrane is installed behind the cladding support battens;
- Moisture is a big issue with timber cladding. Wood will always change dimension slightly due to seasonal changes of humidity and therefore, the cladding design and installation must allow for this by leaving sufficient overlaps, or gaps between flush jointed boards;
- To allow for movement of the timber boards we would recommend that board widths ideally should not exceed 150mm wide, and above 100mm we use two fixings per batten to hold the boards flat;
- Cladding should be installed at typical moisture levels (13 -19%) to minimise movement;
- Openings in the top and bottom of the cladding need to be designed in to allow air to enter and circulate in the cavity behind the timber;
- Nails and/or Screw fixings should be specified as stainless steel to avoid corrosion;
- Ring shank nails have enough give to take up any movement around the fixings in softwood, but hardwood boards should be screwed.
Finishes
- Naked Wood – Hardwoods and some softwoods such as western red cedar, douglas fir or larch can be left unfinished to bleach to a natural silver/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 the cladding is installed. 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 and last as long.
- Preserving Treatments – These are only really necessary for cheap woods. The treatment is best pressure vacuum applied with a boron-based preservative prior to installation (far less toxic to the environment than the old arsenic formulations). If your building 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.
Hardwood
- Oak; Ash; Beech; Birch; Chestnut; Iroko; Maple.
Softwood
- Pine; Cedar; Spruce; Fir; Larch.