Choosing Timber Cladding

Which timber?

The traditional material used for weatherboarding was timber, with oak, cedar, chestnut and larch all being popular choices. However, there are now also a number of treated timbers which are more stable than regular timbers, therefore less prone to warping and movement. These timbers are heat-treated to reduce their moisture content and include Thermowood from Finnforest (finnforest.co.uk) amongst others. Another treated timber, rapidly gaining in popularity, is Accoya. Sustainably sourced, the timber is reacted with acetic anhydride, which is derived from acetic acid — known as vinegar when in its dilute form. This makes very durable and stable. Of course timber is not your only choice. Fibre-cement boards are also now being used, often supplied pre-painted.

Getting the Details Right

It is crucial to get the corner details and those around windows and doors right when it comes to timber cladding, both for aesthetic purposes and to ensure moisture is not allowed to seep behind the boards. The most common way to deal with corners is to fix a length of timber which has been cut into at the back to form a V-shape that fits over the corner. The boards then fix into this piece of timber where they meet the corner. At windows and doors a vertical reveal should be used, protruding out slightly from the weatherboarding, which butts up to it. At all of these details, a mastic seal should be used to prevent moisture getting in.

The alternatives

Shakes and shingles are made from split logs and have an appearance more like timber tiles than boards. Although similar, shingles were originally sawn from a block, whilst shakes were split off using a chisel and mallet. Shingles tend to look neater and more precise than shakes, which give a more rustic appearance. As a cladding material they look fantastic on both contemporary and traditional homes. Shakes are usually made from Western redcedar, giving them good durability, and can also be supplied pressure treated with preservative for enhanced protection. In some areas, shakes or shingles are made from pine.

Need to know: costs

At the cheapest end of the market lies basic softwood boarding, coming in at around just £5-8/m2. However, if left in its raw state it would deteriorate very quickly. It requires regular painting and staining and will need three coats of stain alone when it is installed. When all this is taken into consideration, it is no longer such a cheap option, which makes those timbers that require no staining or treatment, such as eestern redcedar, European larch, douglas fir and even European oak, much more appealing. Cedar will cost around five times the price of untreated softwood, but will last 60 years or so with little maintenance. Larch is often now used in place of cedar or other hardwoods due to its cheaper price. The price of fibre cement boards varies, but expect to pay from around £45/m2 fully installed.

Need to know: Buying & Fitting

Timber merchants, online stores and cladding specialists are all options when it comes to buying your timber cladding. Some claddings come pre-treated, stained or painted, whilst others are supplied ready for you to finish — the cheaper, but more time consuming option. Timber cladding can be – and often is – fitted on a DIY basis, but if you would prefer to leave it to the professionals, then your carpenter will carry out this task. Alternatively, some of the specialists, such as Marley Eternit, offer installation services.

Laying Styles

	SQUARE EDGE This type of boardinghas a uniform thickness, usually between 12-18mm, whilst widths of boards vary from 125mm to 225mm. Many fibre cement boards are square edge.
	FEATHER EDGE Boards are tapered across their width. This style of board produces a rustic, rural appearance that is perfect for more traditional homes, or barn-style self-builds.
	SHIPLAP Shiplap has a shaped front face and profile so that the top of each board fits behind the bottom edge of the adjacent board. It gives a neat finish. Moulded PVC boards are often avialable in this style.
	TONGUE & GROOVE These produce a uniform look that suits contemporary houses. They have a flat face and in the absence of any overlapping, rain is kept out by the way the groove covers the tongue of the board below.

Fixing

Horizontally mounted boards are preferable to vertically mounted ones as they produce greater resistance to moisture penetration. In cases where vertical weatherboarding is used, the overlap should face away from the prevailing wind.

If you’re going for a style where the boards overlap, they should do so by 30mm. Boards are fixed to battens, which should measure 50mm deep and be spaced at a maximum distance of 600mm centres. Battens should be fixed to a breather membrane or vapour barrier.

When fixing the battens, start from the bottom up and leave a distance of 150mm between the bottom edge of the weatherboarding and the ground. Each board should be fixed to at least three battens to ensure stability.