How to Strip and Re-Stain a Timber Deck

By Steve — flooring and wet-areas, Adelaide Hills, 20 years on the tools.

Every Adelaide Hills tradie I respect has the same opinion on belt-sanding a deck: don’t. Sanding a hardwood deck takes 2 mm off the board surface, exposes the soft summerwood between the dense growth rings, and gives you about 2–3 recoat cycles before the boards are too thin to be safe. A 19 mm-thick merbau board started at 19 mm. After three sand-and-recoats, it’s down to 13 mm and the screw heads are cratered.

The proper trade method is chemical stripping followed by a stiff broom and a hose. Done right, it gets the old finish off, lifts the embedded grime, and leaves the timber surface intact at the original thickness. You then re-stain with a penetrating oil-based deck stain — and on Aussie hardwoods (merbau, spotted gum, jarrah, blackbutt) you specifically need oil-based, not water-based, because of tannin bleed.

The tannin issue is what trips up Americans and home-made YouTube guides. US “deck paints” — the thick film-forming products from Behr or Olympic — peel off Aussie hardwoods within one summer. Tannin bleed lifts the paint film from underneath. Cabot’s Aquadeck, Cabot’s Deck and Exterior Stain, Sikkens Cetol Deck or Wattyl Forestwood Deck Stain are the products that work here. They’re penetrating oils, not film-formers, and they shrug off tannin bleed because there’s nothing for the tannin to lift.

I’ve been laying and maintaining hardwood decks across the Adelaide Hills for nearly 20 years. The decks I built in 2008 and recoated faithfully every 3 years are still in beautiful nick. The decks where the owner sanded and recoated every cycle have all needed board replacement by year 12 — the boards too thin to hold a fixing screw, splintering, no margin left. The strip-and-stain method is the difference between a 30-year deck and a 12-year deck.

What you’ll need

• Cabot’s Deck Clean or Wattyl Solvastrip — 4L gets about 25 m² of deck ($50–$70)
• A stiff-bristle deck broom (Sabco Deck Brush or Gala) — $25
• Garden hose with a fan-spray gun (NOT a high-pressure washer — see Step 4)
• Plastic drop sheets to protect plants below the deck
• Long rubber gloves, eye protection, old clothes, enclosed shoes
• Cabot’s Aussie Clear, Cabot’s Deck and Exterior Stain, or Sikkens Cetol Deck — colour matched to your timber ($95 for 4L)
• Quality lambswool applicator on a pole — $35
• A smaller brush for between-board edges — 75 mm
• A dry weather window of 3 days minimum (check BoM)

Step 1: Clear the deck and check the weather

Move every chair, pot plant, BBQ off the deck. Sweep the leaves out of the gaps between boards with a paint scraper or a 5-in-1 tool. Check the BoM forecast — you want at least 3 dry days. Strip on day one, recoat on day three. Rain during the strip is fine; rain on wet stain is a disaster.

Step 2: Wet the deck and apply the stripper

Hose the deck down to wet the boards — stripper works better on damp timber, not bone dry. Pour Cabot’s Deck Clean into a plastic watering can, dilute according to the label (usually 1:3 or 1:4 with water), and pour it evenly across about 5 m² at a time. The product foams slightly as it reacts with old finish.

Step 3: Scrub with the deck broom in the direction of the grain

Working in 5 m² sections, scrub firmly along the length of the boards — never across. The broom bristles need to enter the timber grooves to lift residue. Old grey finish lifts as a brown-grey slurry. Keep moving — don’t let the stripper dry on the boards or it’ll leave streaks.

Step 4: Rinse with the hose, NOT the pressure washer

Standard advice on YouTube: pressure-wash the deck. This is wrong for Aussie hardwoods. A 1500 PSI pressure washer fluffs the soft summerwood between growth rings, leaving a furry surface that holds water and rots prematurely. A garden hose with a fan-spray gun (Hozelock or Pope, $30) lifts the slurry without damaging the surface. Take your time — work along the boards, fan-rinsing the foam off until the water runs clear.

Step 5: Repeat on stubborn sections

Areas with thick old film (under chair legs, around the BBQ, anywhere protected from sun) often need a second coat of stripper and a second scrub. Don’t try to rush this with extra-strong stripper — same product, second pass, more elbow grease. The deck should end up uniformly bare timber, slightly damp, with no patches of old grey film visible.

Step 6: Let the deck dry for at least 48 hours

Hardwood deck boards need to drop to under 18% moisture content before staining or the stain won’t penetrate. In Adelaide summer that’s 24–48 hours. In a Hills winter or rainy stretch, you might need 4–5 dry days. A pin-style timber moisture meter from Bunnings (Trotec or General Tools, $50) tells you when you’re ready — push the pins in across the boards, look for under 18%. If you don’t have a meter: timber should look uniformly pale, no dark damp patches, and the surface should feel dry to a back-of-the-hand check.

Step 7: Sand only the rough spots, by hand

Where the broom raised splinters or where there’s existing damage, hit just those sections with 120-grit sandpaper on a sanding block — by hand, not a belt sander. Lightly. Wipe dust off with a damp cloth and re-check moisture before staining.

Step 8: Apply the first coat of oil stain — thin and along the grain

Stir Cabot’s Deck Stain thoroughly — the pigment settles fast. Pour into a paint tray. Load the lambswool applicator, beat off excess against the tray ridge, and lay the stain along the grain in lengths of 1–2 boards at a time. The first coat penetrates into the timber, not on top of it. Use a small brush to cut the edges along the joists/rebates and to push stain into the gaps between boards. Wipe any pooling stain off after 10 minutes with a clean rag — pooled stain dries shiny and tacky, looks terrible.

Step 9: Wait 24 hours, then second coat

Cabot’s needs 24 hours between coats in dry weather. Don’t try to do both coats in a day — the second won’t penetrate, will sit on top sticky for weeks, and will eventually peel. Same technique on the second coat: thin, along the grain, wipe off any pooling.

Step 9a: Boards that need replacing

While the deck is stripped bare, walk every board and check fixings. A board that flexes more than 5 mm under your foot when you step on it has either failed fixings or rot. Sound boards by tapping with the handle of a hammer — solid timber rings clearly, rotten timber thuds. Replace any rotten boards before staining. Match the species — merbau replacements for merbau decks, spotted gum for spotted gum, etc. Bunnings and Reece both stock standard 90×19 mm hardwood deck boards in the common species. Use 304 stainless decking screws (DeckMate or Buildex) — galvanised screws bleed rust marks down hardwood within a year due to tannin reaction.

Step 9b: Pre-staining check on weather and timber moisture

Don’t stain in direct hot sun. The stain flashes off the surface before it can penetrate, leaving a sticky residue rather than absorbing. Aim for an overcast day, or stain in early morning before the sun hits the deck, or in late afternoon as it leaves. Air temperature between 12°C and 28°C is the sweet spot. Avoid windy days — wind blows leaves and dust onto the wet stain.

Step 9c: Special note on merbau

Merbau (Kwila) is the most common Aussie deck timber and the worst tannin-bleeder. After stripping, hose the deck thoroughly to flush out residual surface tannin — you’ll see brown water running off. Repeat the rinse the next day too. Merbau tannin runs into nearby tiles, concrete and pavers and stains them rust-orange. Lay plastic sheeting under the deck overhang and on adjacent paved areas during the strip and rinse phase, especially on a sloped block.

Step 10: Cure 72 hours before furniture goes back

The stain is touch-dry in 6 hours but needs 72 hours before you put a heavy planter or chair leg on it. Walk on it after 24 hours barefoot if you have to, but don’t drag anything. Re-coat every 2–3 years on a north-facing deck, every 3–5 on a south-facing one. Far less hassle than a full sand-and-strip cycle.

Step 11: Maintenance between full strips

You don’t need to strip every recoat. Years 3, 6 and 9 can be a “wash and recoat” — wash with diluted Cabot’s Deck Clean (1:10 ratio, much weaker than full strip), light scrub, rinse, dry, single coat of stain. Years 12 or 15, when the wash-and-recoat starts to fail, do another full strip. This gives you 30+ years of deck life with minimal board damage.

Step 12: Mould, mildew and shaded decks

South-facing or under-canopy decks accumulate mould and mildew that no amount of staining hides. Treat with a fungicidal wash before stripping — Wattyl Mould Killer or 30 Seconds Outdoor Cleaner, both available at Bunnings, $15–$25 a bottle. Spray, wait 15 minutes, scrub, rinse. Then proceed with normal strip. Mould trapped under stain bleeds back up within a year and turns the deck patchy.

Step 13: When to give up and replace boards

If your deck has surface checking (fine cracks along the grain) deeper than 2 mm, multiple cupped or warped boards, or any rot at the joist contact points, no amount of stripping or staining fixes it. The timber has reached end of service life. Replacing a single deck board is a 30-minute job per board with hand tools; replacing the whole deck surface is $80–$150/m² supply and lay. Better to spend on replacement than chase failing boards with expensive stain that won’t hold.

The Steve rule

The deck is a wear surface, not a piece of furniture. Treat it like one: strip it gently, oil it deeply, recoat it often. The boards last 30 years if you respect the timber, 10 years if you sand them every cycle. Cabot’s, Sikkens, Wattyl Forestwood — pick one and stay with it. Mixing brands between coats is how you get blotchy finishes that no amount of effort can fix.

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