April in the UK means rain, and for garden decking, that means standing water, green algae, and — without treatment — premature rot and warping. The good news is that a single weekend’s preparation every year or two is enough to keep softwood decking in excellent condition for a decade or more.
The approach you take depends on what your decking is made from and what condition it is in right now. Bare or faded softwood needs the most work; composite decking mostly just needs a clean.
Understanding Your Options: Oil, Stain, and Sealant
The three main product categories behave quite differently in practice. Choosing the wrong one — for example, applying a film-forming sealant over a previously oiled deck — can lead to peeling and flaking.
| Product Type | Coverage (per litre) | Typical Cost | Durability | Best For |
|---|---|---|---|---|
| Decking oil (penetrating) | 8–12 m² | £15–£35/litre | 1–2 years | New or bare softwood; feeds the wood |
| Decking stain (semi-transparent) | 8–12 m² | £12–£28/litre | 2–3 years | Adding colour while maintaining grain visibility |
| Decking paint (opaque) | 10–14 m² | £10–£22/litre | 3–5 years | Heavily worn or discoloured decking; hides defects |
| Decking sealer/varnish | 10–15 m² | £14–£30/litre | 2–4 years | Hardwoods; film-forming, less suitable for softwood |
Decking oil is the most forgiving product for UK softwoods like pine, larch, and treated spruce. It penetrates the grain, feeds the wood, and repels water without forming a film that can crack and peel. Reapplication is straightforward because you do not need to strip the previous coat. Most oils are available in clear, natural, or tinted finishes.
Decking stain provides colour and water resistance in one product. It sits somewhere between a penetrating oil and a film-forming paint. Semi-transparent stains preserve the texture and grain of the wood; solid stains cover more imperfections but behave more like thin paint over time.
Decking paint is the right choice when boards are heavily worn, heavily stained, or have lost their surface texture. It provides the most durable waterproof barrier but requires the most prep work and the most effort to re-coat because old paint must be fully sanded or stripped before re-application.
Step 1: Prepare the Surface
Preparation is where most decking projects succeed or fail. New product applied to a dirty, green, or damp surface will not bond properly.
Clean the decking thoroughly. Use a purpose-made decking cleaner, available from builders’ merchants and garden centres for around £8–£18 per litre concentrate (typically diluted 1:10). Apply with a stiff brush or pump sprayer, working along the grain, and leave for 10–15 minutes before scrubbing and rinsing off. Decking cleaners combine a biocide (to kill algae and mould) with a mild acid that opens the grain and removes weathered grey pigment.
A pressure washer speeds up rinsing but should be used on a low setting (below 120 bar) to avoid raising the grain or blowing out the timber between boards. Keep the lance moving and use a fan tip rather than a pencil jet.
Sand if necessary. Weathered or rough boards benefit from a light sand along the grain using 60–80 grit sandpaper. A belt sander or random orbital sander significantly reduces the effort on larger decks. Sanding also opens up the surface to improve oil absorption.
Allow the decking to dry fully. This is non-negotiable. Most products specify the wood must be dry to the touch and have a moisture content below 18–20%. In the UK, this typically means waiting 48–72 hours of dry weather after cleaning. Applying oil or stain to damp timber traps moisture and leads to rapid failure.
Step 2: Apply the Treatment
Work in dry conditions with the temperature between 5°C and 25°C. Avoid direct bright sunlight, which causes the product to dry too quickly on the surface before it can penetrate.
For decking oil, apply with a flat brush or a roller fitted with a short-pile sleeve, working along the grain. Apply a generous first coat and allow it to penetrate for 20–30 minutes before wiping off any excess with a clean cloth. A second coat applied after 4–6 hours will significantly improve longevity. Two thin coats always outperform one thick one.
For decking stain or paint, use a brush rather than a roller for the first coat on rough or profiled boards, as a brush works the product into the grain. Subsequent coats can be rolled for speed. Allow each coat to dry fully before applying the next — typically 4–8 hours depending on temperature and humidity.
Step 3: Add Non-Slip Protection
Wet decking can become dangerously slippery, particularly when algae growth begins in spring. There are two main approaches to improving grip.
Anti-slip decking strips are aluminium or GRP inserts pressed into routed grooves or screwed across the board surface. They provide excellent grip and last the life of the deck. Expect to pay £8–£20 per linear metre depending on the material and width. They are particularly effective on step nosings.
Anti-slip additives are fine grit compounds (often aluminium oxide or fine silica sand) mixed directly into decking oil or paint before application. They add texture to the finished surface without altering the appearance significantly. A 250 g pot — enough to treat 15–25 m² — costs around £6–£12.
For existing decking, proprietary anti-slip coatings that combine grip and weather protection are available at around £10–£20 per litre, covering 6–10 m².
Composite Decking: Much Lower Maintenance
Composite decking — boards made from a blend of wood fibre and recycled plastic — requires considerably less maintenance than softwood. It does not need oiling, staining, or sealing. However, it can still develop a slippery biofilm in wet conditions, and the surface can fade over time without treatment.
Clean composite decking twice a year with warm soapy water and a stiff brush. Avoid abrasive cleaners or pressure washing at high pressure, as these can damage the surface texture. Purpose-made composite deck cleaner (around £8–£15 per litre) is available for more stubborn staining. Some premium composite ranges are marketed as wholly maintenance-free, but annual cleaning will always extend appearance and lifespan.
Building Regulations: Balustrades on Raised Decking
If your decking is more than 300 mm above ground level, Part K of the Building Regulations (Protection from Falling, Collision and Impact) requires balustrades of at least 1,100 mm in height. The balustrade must be designed to prevent children climbing it — horizontal rails that act as a ladder are not acceptable. If the decking adjoins a house in England and Wales, you may also need to check whether permitted development rights apply to the structure, particularly in conservation areas or on listed buildings. Contact your local planning authority if in any doubt before building raised decking.
Maintenance Schedule
A simple schedule helps you stay ahead of the weather.
- Every spring: Clean with decking cleaner, inspect boards for rot or splits, sand any rough patches, check fixings
- Every 1–2 years (softwood oil/stain): Apply a fresh coat of oil or stain after spring clean
- Every 3–5 years (decking paint): Sand back and repaint
- Composite decking: Clean twice yearly; inspect fixings annually
The best time to apply treatment is late spring or early summer — after the worst of the April showers have passed and before summer UV begins to degrade the finish. If you treat in April, choose a dry settled spell of at least 48 hours.
