Decking maintenance before the real summer: what actually matters

Wooden decking in the Cotswolds gets a lot of hope thrown at it and not much actual maintenance. Most people treat it like a patio that happens to be made of wood. It isn't. A patio doesn't rot. A deck does.

Five things to check before the proper heat arrives.

1. Underneath, not on top

The decking boards you can see are usually fine. The thing that fails is the joists underneath, which you can't see. If your deck's been down five years or more, it's worth a look.

Lift a couple of boards at the far corner (the corner that gets least air movement). Take a screwdriver. Press firmly into the top edge of the joist where a board sat. If the screwdriver sinks in 5mm, the joist has started to go. If it sinks 10mm, it's gone.

The joists are the structural part of a deck. Rotten joists mean the deck is at the end of its life, not the middle. Worth knowing.

2. Screws and fixings

Walk the deck slowly. Any loose boards? Any screws that have backed out? Decking screws work loose over time as the wood expands and contracts.

Every loose board is a potential trip. Tightening them takes a screwdriver or an impact driver and five minutes a board. If the screw won't bite (the wood's gone around the fixing), move the screw 10mm to a fresh bit of wood and use a slightly longer one.

3. Algae and the slip problem

North-facing decks go green with algae. Not just ugly, it's a slip hazard that gets worse when wet. The fix:

• Brush the deck dry with a stiff-bristled broom first. Gets the loose stuff off.
• Apply a biological deck cleaner (Ronseal, Cuprinol, or a generic biocide-based product). Cheap, non-caustic, follow the label.
• Leave to work. Usually 24 hours.
• Rinse off with a gentle jet. Not a pressure washer on full power, just a hose. Pressure washers shred the top of decking boards.

That'll clear 90 percent of surface growth. If it's seriously mossy, a second application a week later finishes the job.

4. Oil or stain

Decking oil is the single biggest thing you can do to extend the life of a deck. A deck with a proper oil treatment lasts twice as long as one left bare. The wood stays supple, doesn't crack, sheds water better, doesn't bleach out in the sun.

How often: every 2 years is the honest answer. Most people do it every 4 or 5 and wonder why the boards are cracking.

What to use: a proper decking oil (Cuprinol Ducksback, Ronseal Perfect Finish, Sadolin decking oil, or equivalent). Avoid one-coat products that promise "5 years guaranteed," they're usually thinned-out versions that need a proper topcoat six months in.

Application: two coats, 12 hours between. Dry sunny week. Brush or roller. 4 to 6 hours for a standard 20 square metre deck.

5. Gaps between boards

The gaps between boards should be clear. If they're packed with leaves, dirt, moss, water can't drain off, and you get standing water that rots the joist below.

An old knife or a specialist deck gap tool (tenner at a builders' merchant) pulled down each gap clears them out. Ten minutes on a standard deck. Do it before you clean, not after.

The hot weather question

If the deck's in direct south sun, the boards will get hot enough in July to burn bare feet. This is usually fine once you know, but worth a thought if grandchildren are about. A summer rug over the main sitting area takes the worst out of it without spoiling the look.

Cost

• Inspection and tighten: 45 minutes, rolled into another visit.
• Full clean plus oil, two coats: half a day plus drying time between coats (so a day in total). Around £180 for labour plus £50 to £70 of oil depending on deck size.
• Replace a few rotten boards: dependent on quantity, usually £15 per board material, 30 minutes each.
• Full rebuild on rotten joists: case by case, but budget £1,500 to £4,000 for a standard garden deck.

If you're not sure which category yours is in, send a photo of the surface and a photo from underneath if you can get one. I can usually tell.