How do you maintain wooden decking?
Tips & maintenance · Maintenance
MaintenanceMaintaining wooden decking
Decking is the most heavily used woodwork in your garden: horizontal, unsheltered, and walked on. Two treatments a year keep it alive.
- Clean in spring
- Check in autumn
- Pressure washer on a low setting
Why decking has the hardest time
Every surface is horizontal. Rain does not run off but stays on it until it evaporates.
That is the whole difference from a facade or a fence. On a vertical surface water runs away; on a deck board it lies in every small unevenness and in every crack. On top of that, decking facing north or under trees gets little sun and so dries slowly — exactly the conditions in which algae thrive.
Green algae are therefore the main problem, and not just cosmetically: algae hold moisture against the wood and make the deck as slippery as ice. Decking you do not clean becomes dangerous to walk on in autumn.
The second point is the fixings. Wood shrinks in summer and swells in winter, and that makes screws work loose. Retightening them twice a year takes half an hour and prevents protruding screw heads — which people trip over and where water stands in the screw hole.
A pressure washer at full power blasts away the soft fibres between the growth rings. The result is a rough surface that holds dirt faster and gives you splinters. Work at low pressure, with a wide nozzle, at least 30 cm away and along the grain.
- Cleaning
- spring, and in autumn if needed
- Retightening screws
- twice a year
- Oiling
- every year if you want to keep the colour
- Letting it turn grey
- fine; purely cosmetic
- Pressure washer
- low pressure, wide nozzle, along the grain
- Under the decking
- keep clear of leaves
- Ventilation
- air under the boards is essential
To be fair: wooden decking will keep getting slippery. However well you maintain it, in a wet autumn the algae come back — especially facing north and under trees. If you absolutely do not want slippery decking, you end up with a ribbed profile, anti-slip strips or a different material. Maintenance slows the problem down; it does not solve it.
The decking year
| When | What | Why |
|---|---|---|
| Early spring | clean thoroughly | the winter algae are still on it |
| Spring | retighten screws and fixings | the wood has shrunk after winter |
| Spring | replace loose or cracked boards | before the decking season starts |
| Late spring | oil, if you want to keep the colour | dry weather, no full sun |
| Summer | sweep and deal with stains straight away | grease and wine soak quickly into warm wood |
| Autumn | remove leaves, underneath too | leaves hold moisture and speed up rot |
| Winter | sweep now and then | a layer of wet leaves on the wood is the worst situation |
How to clean your decking
- Clear and sweepTake everything off, and sweep out between the boards with a thin scraper or a decking brush. That is where the algae that give you the most trouble sit.
- Wet itEspecially if you use a cleaner: on dry wood the product soaks in straight away and works unevenly.
- Apply cleanerA decking cleaner or green soap, left to work as stated on the label. No bleach — it attacks the fibres and bleaches the wood unevenly.
- Brush along the grainA stiff brush on a handle. This is the job people grab the pressure washer for, and where the brush is actually better.
- RinseThoroughly, so no cleaner residue is left behind. Residue can get in the way of the later oil treatment.
- Let it dryAt least 48 hours of dry weather before you apply oil. Oil on damp wood stays sticky on the surface.
- Oil if you wishThinly, along the grain, and wipe off excess oil after a quarter of an hour.
In pictures · Six common problems
Schematic drawing.
Six common problems
Green algae
Clean and provide more light and air circulation. Pruning overhanging branches often does more than the cleaner itself.
Protruding screws
Retighten, and for a screw that no longer bites: a thicker screw or a new hole a centimetre to the side.
Splinters in bare feet
Sand lightly with 80 to 120 grit, locally where it is rough. With softwood this comes back every few years.
Warped board
Usually not fixed well enough or not supported enough. Extra screws or an extra joist underneath solves it; a badly warped board you replace.
Black stains
Often a reaction between tannic acid and iron. Use different screws and sand the stain out or bleach it with oxalic acid.
Water stands
The decking has too little fall or the gaps between the boards have silted up. A few degrees of fall and open gaps are not a luxury.
Nobody sees the substructure, and that is usually where it starts. Leaves and soil that build up under the boards keep the joists permanently damp. Looking underneath once a year and sweeping it out saves years.
Frequently asked questions about maintaining wooden decking
How often should I clean my decking?
Thoroughly once a year, in early spring. In a wet autumn or under trees, a second clean is no unnecessary luxury.
Can I use a pressure washer?
At low pressure, with a wide nozzle, at least 30 cm away and along the grain. At full power you blast away the soft fibres and the wood becomes rough.
Should I oil my decking?
Only if you want to keep the colour. Untreated, it turns grey and stays structurally sound. Oiling does mean coming back every year.
How do I get rid of green algae?
With a decking cleaner or green soap and a stiff brush, along the grain. No bleach: it attacks the fibres and bleaches unevenly.
Why do the algae keep coming back?
Because the decking dries slowly. More light and air circulation help most — pruning overhanging branches often does more than any product.
What do I do about splinters?
Sand locally with 80 to 120 grit. With softwood species this comes back every few years; with hardwood rarely.
More maintenance
Maintenance is worked out separately for each wood species and each element.
Have a question about your project? Just ask — we're happy to help.
Photos via Wikimedia Commons: Green algae on grooved deck boards in winter — Fabian Horst, CC BY-SA 4.0 · Weathered deck boards with shrinkage cracks and screw heads — nywriter21 (Flickr), CC BY 2.0
The Wood Guide
More in Care & finishing
- Maintaining a wooden pergola
- Maintaining a wooden house
- Maintaining wooden doors and windows
- Maintaining wooden cladding
- Maintaining a wooden worktop
- Giving your picnic table a makeover
Other sections:Wood speciesUnderstanding woodChoosing & buyingBuild it yourselfTrees & forests