Fitting wood facade cladding

Wood is the only cladding material that carries on changing once it is up. That is exactly why people choose it, and sometimes exactly why they regret it later. I fit wood facade cladding on houses, extensions, outbuildings and sheds, from a single storey to a complete facade, and I say beforehand how it will look rather than afterwards.

The overview page on facade cladding puts the materials side by side. This page is only about wood: which species, which profile, vertical or horizontal, and what weathering does to your facade.

Timber species and what you can expect from them

The species decides three things at once: how the facade looks now, how much you have to do to it later, and what it costs. They are not simply interchangeable.

Douglas fir

Douglas fir is a warm red brown when it is new, widely available and the most affordable of the four. For a lot of facades that is the obvious choice. The heartwood can stand outside untreated. Watch two things. Douglas moves a fair bit, so the boards shrink and swell with the season. And the knots can bleed resin that works its way out on the sunny side. On a tight, flat look that shows. On a rural facade it belongs there.

Thermowood

Thermally modified wood is heated in a kiln, with nothing added. That makes it take up less moisture, move less, and keeps a long vertical board straighter than untreated wood does. On handover it is dark brown. That colour is not permanent, though. The drawback of the treatment is that the wood has turned more brittle, so pre-drilling and screwing gently is not a luxury. I allow extra time for that.

Oak

Oak is the heaviest and the dearest of the four and lasts the longest. There is one thing about it you need to know beforehand: oak contains tannin. Rainwater that runs over oak and then lands on brickwork, concrete or paving leaves dark streaks that do not simply come off. So the fixings have to be stainless, and I check beforehand where the water off the bottom row runs to. An oak facade above a pale tiled floor is asking for staining.

Cedar

Western red cedar is light in weight, moves little and stands up to damp well by nature. That makes it suitable for long boards and for facades where you want as little movement as possible. It is soft, though. A ladder leaning against it or a wheelbarrow scraping past leaves a dent. At eye level along a path it would not be my first pick, higher up the facade it is not an issue.

Profiles: rhombus, shiplap and flat boards

The profile decides the look more than the species does. Four come past most often.

Rhombus has bevelled edges and an open joint between the boards. That gives a clean facade with a fine shadow line. There is one requirement to it: through that open joint you look at whatever sits behind. A black breather membrane belongs there, and the batten frame has to be dead true, because every deviation comes back at you in the shadow line right across the facade.

Shiplap is the classic profile with overlapping boards. It sheds water by itself, is more forgiving of a substrate that is not perfectly straight, and suits a more rural look.

Swedish rebated boards sit in between. The boards lap into each other on a rebate and hold a shadow joint, and that keeps working when the wood shrinks in summer.

Flat boards with concealed fixings give the quietest look, with no screws in sight. It is at the same time the least forgiving version, because anything out of line shows straight away.

Vertical or horizontal

Fitting vertically changes more than the look alone. Water runs down along the grain instead of sitting on a joint, and it makes a facade look taller. The catch sits behind it. With vertical boards the batten frame runs horizontally, and horizontal battens hold moisture and block the ventilation. So I lay a second layer of battens across them at right angles. That costs material and time.

Fitting horizontally is simpler, because then the battens stand vertically and the cavity ventilates from the bottom up on its own. It makes a facade look wider and lower. The weak point is the end grain at the joints and at the window frames, because that is where water gets in fastest. I treat those ends separately before the boards go up.

Which it becomes depends more often on the shape of the facade than on taste. A tall, narrow facade with a dormer asks for something different than a long, low extension.

The look of wood without wood

Sometimes someone wants the look of wood, but not the change that comes with it. Then cladding in a wood look is a more honest answer than wood you try to keep in check with stain. You get a grain that stays as it is. What you do not get is the depth and the smell of real wood, and up close you see the difference. I would rather say beforehand which of the two fits what you expect than have you find out later.

Weathering grey, and why I always ask about it

Wood goes grey. All four species above, treated or not. Sunlight breaks down the substance that gives wood its colour and what is left is silver grey.

The awkward part is not that it happens, but that it does not happen everywhere at the same time. The south and west sides run ahead. Under an overhang and behind a downpipe the wood stays darker for longer. So a facade spends a while in an in-between stage where it looks patchy, and that is the stage people misjudge.

For one person that is the whole idea. Weathered silver grey wood next to zinc, thatch or dark brickwork is a deliberate choice and only gets better. For another it is a disappointment, because the warm red brown of the first week was what they had in mind when they said yes. Both are fine, but they are not the same decision.

So I ask it outright before anything is ordered: do you want the facade to stay the way it is on day one, or do you like grey? If you want to keep the colour, that means a pigmented oil or an opaque stain, and the commitment to come back to it at intervals. If you like grey, you can leave the wood untreated and there is nothing to do to the wood itself. There is a middle road as well: a weathering agent that speeds the process up and makes it more even, so you skip the patchy in-between stage.

Maintenance

Untreated wood asks for no maintenance to the wood itself. What does need attention is the rest: the fixings, the junctions at the window frames and the roof edge, and the north side, where green growth builds up on the spot that never dries out in the wind.

Two things do most of the damage here, and both are avoidable. The first is the pressure washer. It eats the soft layers out of the wood and leaves a rough surface that holds dirt all the better. A soft brush and water are enough. The second is the bottom row sitting against the paving or the ground. Splashing rainwater and soil keep that wood permanently wet, and that is where the rot starts. There should be a gap under the bottom row, and that gap has to stay clear.

What sits behind the boards

The part nobody sees decides whether a timber facade holds up. Behind the boards sit the batten frame, a breather membrane and a cavity that is open at the bottom and at the top, so the air can pass through it. If that cavity dead ends, the back of the boards never dries and you have a problem you cannot see coming from the outside.

On the cladding on an upper floor the work sat exactly there. That facade is not done in wood but in flat panels, only the junctions are the same question: running the cladding neatly around the existing window frames and closing off the junction under the roof edge. The photos were taken while the work was going on, with the mobile tower still against the facade.

How I go about it

I come and look, measure the facade up and go through the four choices with you: species, profile, direction and finish. After that you know what the look will be and what you get back from it later. I only order the wood once those choices are fixed, because turning a facade around when the boards are already on the doorstep is expensive.

The junctions are carpentry to measure, and that is the part that goes wrong for people who only hang the boards. If it is about an extension or annexe, I would rather take the cladding along in the same job, so the junction with the existing house stays in one pair of hands. And if an existing timber facade only needs a few loose repairs, that falls under handyman work and maintenance and nothing has to be replaced.

If you do not know yet which way you want to go, send a few photos of the facade and whatever measurements you have. Put it to me through the contact page, and I will say what I would do, even if the answer is that wood is not the best choice here.