Treat a shed with wood preservative

Clean, treat and protect a garden shed with wood preservative in one dry afternoon session.

SP-01Pick a dry, mild dayCheck the forecast for a dry day, ideally 10-20°C, with no rain forecast for at least 24 hours after you finish. Avoid strong sun or wind, which dries the preservative too fast and causes patchy coverage. Most preservatives need the wood dry to the touch, so skip this job after heavy rain.

SP-02Clear the area and protect nearby plantsMove anything stored against the shed walls so you can reach all sides. Cut back plants or grass touching the timber and lay a dust sheet over nearby borders to catch drips. Preservative can scorch leaves and grass, so keep it off anything green.

1 each · Dust sheet or old bedsheet

Buy:Tooled UpB&QAmazon

SP-03Brush down the whole shedUse a stiff brush to remove cobwebs, moss, loose dirt and flaking old paint or preservative from all timber surfaces. Pay attention to the roof edges, corners and the base, where debris builds up. A clean surface lets the new preservative soak in properly.

1 each · Stiff outdoor brush

Buy:Tooled UpB&QAmazon

SP-04Scrape off any flaking coatingWhere old paint or preservative is peeling, scrape it back with a paint scraper until you reach sound timber or a firmly bonded coating. You don't need to strip the shed bare, just remove anything loose. Sand rough patches lightly so the new coat goes on evenly.

1 each · Paint scraper

Buy:Tooled UpB&QAmazon

1 sheet · Sandpaper, medium grit

Buy:Tooled UpB&QAmazon

SP-05Mask fittings and glassCover door hinges, handles, window glass and any metal fittings with masking tape so preservative doesn't stain or gum them up. If the shed has felt roofing, tape along the edge where felt meets timber to keep the line neat.

1 roll · Masking tape

Buy:Tooled UpB&QAmazon

SP-06Stir the preservative and do a test patchStir the preservative thoroughly, as the pigment settles at the bottom of the tin. Brush a small test patch on a hidden panel and check the colour once dry, since it often looks darker wet than it ends up. Wear gloves throughout, as most preservatives irritate skin.

1 each · Wood preservative, 5L

Buy:B&QAmazon

1 pair · Disposable gloves

Buy:Tooled UpB&QAmazon

SP-07Apply the first coatWork from the top of each wall downward, following the grain of the wood, and finish one full panel before moving to the next to avoid overlap marks. Get into joints, corners and the underside of overlapping boards where rot usually starts first. Don't overload the brush; two thin coats cover better than one thick one.

1 each · Natural bristle paintbrush, 75mm

Buy:Tooled UpB&QAmazon

SP-08Let the first coat dryLeave the shed for the drying time stated on the tin, usually 2-4 hours, before touching it or applying a second coat. Keep pets and children away from the treated surface while it's wet, as most preservatives are toxic until fully dry.

SP-09Apply a second coatRepeat the brushing process for full coverage, especially on end grain, roof edges and the base of the walls, which soak up the most water in wet weather. Two coats give much better protection than one, even if the first coat looks even.

1 each · Wood preservative, 5L

Buy:B&QAmazon

SP-10Remove masking and clean upPeel off the masking tape once the final coat is dry to the touch, before it bonds too firmly. Clean brushes in white spirit if the preservative is solvent-based, or with water if it's water-based; check the tin. Let the shed dry fully, usually 24-48 hours, before storing anything back against the walls.

1 500ml · White spirit

Buy:B&QAmazon

SP-11Dispose of rags and empty tins safelySolvent-soaked rags can self-heat and catch fire in a bin, so lay them flat outside to dry fully before binning them, or soak them in water in a metal container. Take empty preservative tins to your local council recycling point rather than the general bin, since most councils treat them as hazardous waste.

RULES

KNOW THE RULES

Councils generally class solvent-based wood preservative tins as household hazardous waste — check your local council's disposal rules rather than binning them with general rubbish.

KNOW THE RULES

Before you start: Do I need planning permission for a garden room or outbuilding?

PART OF A BIGGER PROJECT

Refresh a garden shed

Tooled Up links are affiliate links: if you buy after clicking, we may earn a small commission at no extra cost to you. B&Q and Amazon links are plain searches and earn us nothing.

Save this as a project

Back to all guides

Related guides