You never fix timber cladding straight onto the wall. You build a framework of battens first, so that an air cavity of at least 20 mm forms behind the boards where air can travel from bottom to top. That cavity, open at the bottom and at the top, is the difference between a façade that lasts thirty years and one that rots out within five. Budget roughly £45 to £80 per m² in materials for a timber façade if you do the work yourself.
The fitting itself is well within reach of a handy DIYer. The hard part is not the screwing, it is the details: the cavity depth, the batten thickness, the clearance to the ground and to the roof edge, the ventilation openings and the way you let the timber move. That is where it goes wrong in practice, and you only find out years later.
Below is the whole story: which timber, which profile, how you build the frame behind it, all the sizes, the step by step, the detailing, the costs and the mistakes to avoid.
Why a ventilated façade is half the job
A timber façade is not a waterproof skin. It is a rain screen. The idea, known in the trade as the rainscreen principle, is simple: the cladding catches most of the rain, and the little water that does get behind it has to be able to dry out again.
Air does that drying. Warm air rises up the cavity and carries the moisture out with it. Close the cavity off at the bottom or the top and that air stands still, the moisture stays put and your timber rots from behind. Exactly on the side you never get to see.
That is why three rules are non-negotiable:
- At least 20 mm of clear air cavity between the back of the boards and the substrate. In the UK, guidance for timber cladding usually puts the batten depth at 25 mm, which gives you a bit of margin. Source: AKU Woodpanel, a Dutch timber cladding supplier
- Open at the bottom and at the top, so the air can flow through.
- Vertical air paths. Vertical cladding needs horizontal battens, and those block the rising air. Solve it with a double (counter-battened) layer or with profiled ventilation battens. Source: Gadero, a Dutch timber merchant
That third point is the one most often forgotten. If you want vertical boards, you have to budget for two layers of battens. That costs extra timber and extra depth, but it is not optional.
Keep the openings themselves generous too. Insect mesh at the bottom and a vented profile at the top eat into the free opening area, so allow more than you think you need rather than less.
Do you need planning permission?
Short answer: often not, but there are enough exceptions that you should ask first.
Cladding changes the look of your house. As soon as the street scene changes, the odds of someone having a say go up. Going from a brick wall to a timber façade is a noticeable change.
In England, cladding the exterior of a house is generally permitted development under Class A, as long as the materials are of a similar appearance to those of the existing house. Swapping brick for timber is exactly the point where that test gets awkward, because the appearance clearly changes. And on designated land, cladding with timber is specifically excluded from permitted development altogether.
A few situations where you ring the local planning department before you do anything else:
- Conservation area, National Park, National Landscape (AONB), the Broads or a World Heritage Site. Cladding the exterior with timber is not permitted development on that designated land. You need an application.
- Listed building. You need listed building consent, inside or outside, front or back. Always.
- Flat or maisonette. Permitted development rights for houses do not apply. Assume you need permission.
- Leasehold, or a shared freehold with a management company. On top of the council, you need the freeholder’s consent. The external walls are almost never yours alone.
- An Article 4 direction. Some councils remove permitted development rights for whole streets. That is not visible from the pavement, so you have to check.
Do not assume it is automatically permission-free because you are “only hanging up some panels”. In Dutch case law on permission-free building it was established that cladding covering practically the whole façade does not count as a single façade panel. The logic travels: the scale of the work decides, not the word you use for it. Source: PONT Omgeving Source: De Margaretha
Rules differ in Scotland, Wales and Northern Ireland, so check your own authority. Just ring the council and describe what you want to do, with photos. That costs you fifteen minutes and stops you having to strip a finished façade back off. If you want it in writing, apply for a lawful development certificate.
Fire classification: the bit most DIYers skim over
A façade has to meet a reaction to fire classification. The system is EN 13501-1, running in Euroclasses from A1 (non-combustible) down to F.
For a normal two-storey house, solid untreated timber cladding is not a problem. The restrictions kick in with height. In England, combustible materials are banned in the external walls of relevant buildings over 18 m, and separate guidance in Approved Document B applies to residential buildings between 11 m and 18 m. If your project is a block of flats, or anything taller than a house, get that checked by someone who does it for a living before you buy a single board.
For comparison: in the Netherlands new build requires class D as a baseline for façade cladding, and above 13 metres, plus for the lower part of the façade, class B is often required. Source: Vandentop Tuinhout
For an ordinary family home or a garden building this is usually fine: solid untreated timber often reaches class D without any fire retardant treatment. Two things worth remembering:
- The requirement applies to the whole façade system, not just the boards. So the battens, the insulation, the membrane and the substrate all count. Source: HIB Gevels
- Ask your supplier for the test report or declaration of performance for the product you are buying. Then you have it on paper.
Which timber do you choose?
This is the decision that sets your lifespan and your maintenance. Look at the durability class under EN 350: class I is the most durable, class V the least.
| Timber | Durability | Life as cladding | Character |
|---|---|---|---|
| Western red cedar | Class I-II | Around 20-25 years | Light, very stable, lovely colour, pricey |
| Siberian larch | Naturally durable | Around 15-20 years | Hard and heavy, silvers nicely, resinous |
| Thermally modified timber (thermowood) | Much improved | Around 15 years | Sugars and resins baked out, so nothing left to feed fungi |
| Treated spruce or pine | Class IV-V untreated | Only worth it with treatment | Cheapest option, moves more |
| Radiata pine (modified) | Improved | Medium | Alternative to tropical hardwood |
Source: Gevelbekleding-info Source: Foreco Source: Gadero
Thermally modified timber is heated to around 210 degrees during treatment. That drives out the sugars, carbohydrates and resins, so fungi and insects no longer find anything to feed on. Source: Gevelbekleding-info
My rule of thumb: choose untreated durable timber that you allow to silver. Then you have zero painting to do. If you really want a colour, accept that you will be back every 5 to 8 years, up ladders, along an entire elevation.
Watch the weight too. Timbers vary considerably in weight, and that decides how substantial your frame and your fixings need to be. Source: Gadero
Which profile: splayed, lap, channel or open?
| Profile | Fitting | Water shedding | Watch out for |
|---|---|---|---|
| Splayed rebated board (rabat) | Horizontal | Very good, water runs off | The classic; leave 2-3 mm play |
| Overlapping weatherboarding (lap boarding) | Horizontal | Very good | Sturdy look, lots of overlap so more timber |
| Channel siding / log-effect board | Horizontal or vertical | Good | Needs a double batten layer if vertical |
| Rhombus / open-jointed cladding | Either | Water gets behind the boards | Breather membrane compulsory, minimum 6 mm joint |
Source: Gadero Source: Gevelbekleding-info
Two practical considerations:
- Vertical sheds water faster along the grain and reads as slimmer.
- Horizontal silvers more evenly and is easier to fit single-handed, because you use the previous board as a rest.
With an open-jointed façade (rhombus, with visible gaps) a water-resistant, vapour-permeable breather membrane behind the boards is not a luxury but a necessity: water will get behind the boards, guaranteed. With closed overlapping profiles you can sometimes leave it out, but with insulation behind it you want it anyway. For open-jointed work use a UV-stable façade membrane, usually black, so the joints stay dark and the membrane does not go brittle in a few years. Source: Gevelbekleding-info
The build-up from outside in
This is what a proper ventilated timber façade looks like, from outside in:
- Cladding boards
- Battens (vertical, for horizontal boards)
- Second layer of counter-battens if needed (for vertical boards)
- Air cavity of at least 20 mm, open at bottom and top
- Water-resistant breather membrane (for open-jointed work and wherever there is insulation)
- Insulation boards if you are insulating
- Existing wall or timber frame
Important: the cavity sits between the boards and the membrane or insulation. So the insulation must not squash the cavity shut. Add that depth on literally, on top of everything else, if you are insulating.
All the sizes in one place
This is the table you want pinned up by the saw horse.
| Element | Size | Why |
|---|---|---|
| Batten thickness | About 1.5x the board thickness (so around 27 mm for 18 mm boards) | Gives enough airflow behind the façade |
| Air cavity | At least 20 mm clear | Moisture removal and drying |
| Batten centres | Maximum 600 mm, 400-500 mm recommended | Stops sagging and rattling |
| Gap between boards | 2-3 mm | Timber moves with moisture and temperature |
| Joint width, open-jointed façade | Minimum 6 mm | Ventilation and drying |
| Clearance to ground level | Minimum 300 mm | Prevents splash-back and rot along the bottom |
| Clearance to roof edge | Minimum 20-30 mm | Air outlet at the top |
| Nail length | 2.5x the board thickness (so 45-50 mm for 18 mm) | Enough grip |
| Nail position | Around 30 mm up from the bottom edge, and about a third down from the top | Lets the timber move without splitting |
Source: Gadero Source: Gadero, 12 mistakes Source: Gevelbekleding-info
Fixings: use stainless steel. Galvanised material corrodes in damp conditions and then you get rust streaks down your whole façade within a couple of years. Source: AKU Woodpanel
Use stainless ring shank nails or stainless façade screws, and go for A4 (316) rather than A2 (304) with tannin-rich timbers like oak and larch, or near the coast. One fixing per batten for boards up to about 90 mm wide, two for wider boards and for less stable timbers. Source: Gadero
Step by step: fitting timber cladding
1. Assess the substrate
Walk the elevation. Loose render, cracks, rising damp, a broken gutter? Sort that first. You are about to cover everything underneath, so whatever you skip now, you will not see again for years.
Work out what you are fixing to as well: a cavity wall, a solid wall, or timber frame. That decides your fixings and your plugs.
2. Set out on paper
Measure the elevation and draw it up, windows and doors included. Decide:
- How many board widths fit exactly (so you do not finish on a 30 mm sliver).
- Where the battens go, using the window frames as your fixed point.
- How you finish the corners.
Working out in advance how the sizes land around windows and corners avoids ugly infill pieces and weak junctions. Source: Gadero, 12 mistakes
3. Let the timber acclimatise
Store the boards flat and in the shade, and cover the top of the stack in very wet weather. Timber fitted soaking wet or bone dry will move after fitting and pull your joints out of line. Source: Gadero
4. Treat the battens first
The battens are part of your façade and will hang in a damp cavity for thirty years. Treat them on all faces before fitting, or use naturally durable or treated timber. Untreated battens are one of the classic mistakes. Source: Gadero, 12 mistakes
5. Fit membrane and insulation if you are using them
Insulating at the same time? Then fit the insulation boards tight to the wall with no gaps, and run a water-resistant breather membrane over the top, lapped from the top down like roof tiles. Only then do the battens go on.
6. Set the battens level and in one plane
Set the outermost battens first, run a string line, and fit the rest in between at a maximum of 600 mm centres. Pack out any unevenness in the wall with packers: your frame has to sit in one plane, or you will see every bump reflected in the finished façade.
Make sure the battens do not block the ventilation at the bottom and the top.
7. Form the bottom detail
Start at least 300 mm above ground level. Fit a vented profile or insect mesh across the full width at the bottom, so air can get in but mice, wasps and birds cannot. Splay the bottom edge of the lowest board (around 60 degrees) so water drips off instead of tracking back inwards. Source: Gadero
8. Fit the first board and check it
The first board sets everything. Get it dead level (or dead plumb for vertical boards) and check it three times. A millimetre out at the bottom becomes a centimetre out at the top.
9. Work up, leaving play
Slide splayed or channel boards together loosely, with 2-3 mm of room for expansion. Do not drive nails in too deep, especially with a nail gun: on softer timbers you lose your grip. Source: Gadero, 12 mistakes
Check you are still level every five or six boards.
10. Finish the details
Corners, roof edges, window junctions and the top course are the real craft. See below.
The details that decide whether your façade lasts
Bottom edge. Never down to the ground or the paving. At least 300 mm clear, and a splayed drip edge under the lowest board.
Top edge. At least 20 to 30 mm clear of the roof edge so air can get out. Finish with a vented profile or mesh.
Corners. Two options: a corner profile or corner bead that the boards butt into, or a mitre. A mitre looks better but opens up as the timber shrinks. Outside, a corner bead is far more forgiving.
Window and door frames. Fit a drip or flashing above the frames, and do not run the cladding tight against the frame. Leave a joint with room for movement, and make sure water can find its way back out.
Penetrations. Around air vents, outside taps and sockets, build a proper surround rather than cutting a hole that will hold water.
Hanging things on it. Hang nothing heavy off the cladding itself. Fix a light, a camera or a washing line to the structure behind, with a spacer so the cavity stays open.
Costs: what does timber cladding cost to fit?
| Item | Indication |
|---|---|
| Timber cladding materials, fitted yourself | Around £45-70 per m² |
| Thermally modified timber | Around £35-80 per m² |
| Battens, membrane, stainless fixings, profiles | Allow £10-17 per m² on top |
| Supplied and fitted, including insulation and labour | Around £130-175 per m² |
Source: Gevelbekleding-info Source: Gevelbekleding-info, durability
Doing it yourself, add 10 to 15 percent for waste, and more if you are working with short boards and lots of windows. Do not forget access: hiring a tower scaffold quickly runs to a couple of hundred pounds for a week, and that is the cheapest safety you will ever buy.
Insulating at the same time? Then this
You open up a façade once every thirty years. If the cladding is coming off anyway, or going on for the first time, that is the moment to add external wall insulation.
Two technical points first, because these apply wherever you live. The insulation must not squash your air cavity shut, and you have to carry the new thickness of the façade build-up through into the detailing at the roof edge, the window frames and the sills. A wall that gets 120 mm thicker means new window sills and a reworked roof overhang.
In the UK. Re-cladding usually counts as renovating a thermal element under the Building Regulations. If you are working on more than half the surface of the wall, Approved Document L expects you to bring the wall up to a U-value of 0.30 W/m²K, and the work is notifiable to building control. Grants are limited and are aimed at installed work, not DIY: ECO4 and the Great British Insulation Scheme depend on your household and property qualifying, and the work must be done by a TrustMark registered installer working to PAS 2035. Check what you actually qualify for before you order anything, because the schemes and their conditions change.
In the Netherlands. There it runs through the ISDE scheme. The new insulation material must have an insulation value (Rd) of at least 3.5 m²K/W, and the grant applies from around 10 m² up to a maximum of about 170 m². The amount is in the order of €20 per m² for a single measure, and roughly double that if you combine two or more measures. Source: Slimster Source: RVO
Two things to establish beforehand either way, because this is where applications fall over:
- Whether you are allowed to do the work yourself and still get the money, or whether a registered firm has to carry it out.
- The exact amounts and conditions for this year, because they are revised annually.
Maintenance: what does a timber façade ask of you?
Untreated durable timber silvers and asks for virtually nothing. But do this, once a year:
- Walk the elevation and check the bottom 500 mm for green growth and damp.
- Clear the ventilation openings at the bottom and top of leaves, cobwebs and insect nests. A silted-up bottom edge is the most common cause of rot in an otherwise perfectly good façade.
- Check that nothing is growing against it. Ivy and shrubs keep the wall wet.
- Look for nails or screws working their way out and drive them back.
Got an opaque paint or stain on it? Then the cycle is usually 5 to 8 years, shorter on south and west elevations than on north.
The ten mistakes that cost you your façade
- No cavity, or too tight a cavity. Under 20 mm and the façade cannot dry.
- Cavity closed off at the bottom or top. Without an inlet and an outlet, a cavity is worthless.
- Horizontal battens under vertical boards with no second layer. The air cannot get up.
- Battens too thin. Reckon on about 1.5x the board thickness.
- Untreated battens. They rot away sooner than your cladding does.
- Galvanised instead of stainless fixings. Rust streaks within two years.
- No play between the boards. Timber moves; without room you get cupping and splits.
- Cladding taken down to the ground. Splash-back guarantees rot along the bottom.
- Nails driven in too deep. Loss of grip, especially in softer timbers.
- Skipping permission and consents. That can cost you the whole façade.
Frequently asked questions
How much space should there be behind timber cladding?
At least 20 mm of clear air cavity, with open ventilation at the bottom and the top so air can flow upwards. That airflow carries the moisture away. With no cavity, or with no ventilation openings, moisture sits behind the boards and the timber rots from the back.
What batten thickness do I need?
Reckon on about 1.5 times the thickness of your cladding board. With 18 mm boards that puts you at battens of around 27 mm. Fix them at a maximum of 600 mm centres, with 400 to 500 mm the recommended spacing for a crisp result.
Can you fit timber cladding yourself?
Yes. With a spirit level, a cordless drill driver, a decent saw and safe access, this is well within reach of a handy DIYer. Fitting the boards is not difficult. The hard part is the detailing: the cavity, the ventilation, the corners, the window junctions and the finish at the roof edge. Work that out on paper first.
Do I need planning permission for timber cladding?
On a house, cladding the exterior is often permitted development, provided the materials are of similar appearance to the existing house. Going from brick to timber is exactly where that test gets awkward. On designated land (conservation area, National Park, National Landscape, the Broads, a World Heritage Site) timber cladding is excluded from permitted development, listed buildings need listed building consent, and flats have no such rights at all. Ask your council before you order materials.
Which timber is best for cladding?
Western red cedar (durability class I-II) lasts around 20 to 25 years as cladding and barely moves, but it is expensive. Siberian larch is harder and heavier with high natural durability and reaches around 15 to 20 years. Thermally modified timber gets about 15 years and is a good middle road. Untreated spruce is not suitable without treatment or modification.
Do you need a membrane behind timber cladding?
With an open-jointed façade with visible gaps (rhombus) a water-resistant, vapour-permeable breather membrane is essential, because water will get behind the boards, guaranteed. With closed overlapping profiles you can sometimes do without, but as soon as you add insulation, or you simply want the certainty, fit the membrane. Always use a vapour-permeable one, or you will trap the moisture instead.
How much does timber cladding cost per m²?
Doing it yourself, materials work out at roughly £45 to £70 per m², with battens, membrane and stainless fixings on top of that. Supplied and fitted, including insulation and labour, is more like £130 to £175 per m². If you are doing it yourself, allow for waste and for scaffold hire as well.
Taking on your own façade? Then before you order the first board you want to know exactly how many boards, battens and metres of profile you need, and what the junctions at the roof edge, the corners and the windows look like. That saves you a pile of offcuts and a lot of head-scratching halfway through. At fredsdiyplans.com you will find building plans with a material list and a cutting list, so your project is right from day one.