Deck Coats & Coverage Calculator

Depends on product + wood condition. Cabot Australian Timber Oil at 200 sqft/gal baseline on medium-porosity weathered wood: first coat (0.80 × 0.90 × 200 = 144 sqft/gal effective) = 2.8 → 3 gal. Second coat at 220 sqft/gal effective = 1.8 → 2 gal. Total 5 gal × $52 = $260 (plus 1 gal extra = $312 grand total). Behr DeckOver (heavy at 75 sqft/gal) same scope = 12 gal × $48 = $576. Cheaper budget brands save 20-40% but recoat sooner.

No — each subsequent coat covers MORE area because the surface is sealed. Second coat goes ~10% farther than the first. Third coat ~15% farther. Fourth coat ~20% farther. This is opposite to what most people assume. Reason: wood absorbs the first coat heavily (porosity); subsequent coats sit on top of the sealed surface and spread thinner + more evenly. Calculator handles this automatically.

Yes — on bare wood. Deck paint needs primer to bond properly + prevent peeling. Generic deck primer covers ~250 sqft/gal at $32/gal. For a 400 sqft deck = 2 gal primer ($64). Skip primer ONLY when painting over previously-painted surface that's in good shape. The 'previously-coated' surface-condition option flags this and skips the primer warning. Stains don't need primer (they penetrate, not sit on top).

Rough-sawn or weathered wood has higher porosity — 40% less coverage on the first coat (0.60× multiplier). The wood literally drinks the stain through capillary action because the surface has been opened up by weathering + UV degradation. Smooth dressed lumber loses only 0-20% (porosity 1.00× or 0.80×). For weathered + high-porosity wood, expect to budget 30-50% more product than the manufacturer's spec sheet says. The calculator's wood-porosity slider captures this exactly.

Yes — and it lasts 2-3× longer than semi-transparent stain (5-7 yr vs 2-3 yr). But paint hides the wood grain entirely (looks like a painted floor). Best for badly weathered decks where the wood is too far gone for stain. Requires primer on bare wood. Most failure mode: paint peels in sheets on PT pine if humidity wasn't right at application — wait for 3 dry days + use a moisture meter (<15% before painting). Calculator covers paint via 'deck-paint' product type + primer toggle.

Thompson's WaterSeal clear sealer at 175 sqft/gal, 1 coat, $32/gal. For 400 sqft = 3 gal = $96 total. Won't add color but extends life 1-2 yr. Olympic Elite at 250 sqft/gal in semi-trans = 2 gal × 2 coats = 4 gal × $38 = $152 — adds color + UV protection but recoat in 2-3 yr. Cabot Australian Timber Oil at 200 sqft/gal 2 coats = ~$260 — premium that lasts 3-4 yr. Annual sealing budget for cheapest option is ~$50-60 covering wear-and-tear vs $200-300 every 3 years for premium.

2-3 years on horizontal deck surfaces, 4-6 years on vertical railings (which see less wear). Cabot's penetrating oil formulation drinks into the wood (best for cedar, redwood, IPE) rather than sitting on top like paint. Recoat schedule: every 2 yr for high-traffic decks in sun, every 3-4 yr for shaded covered decks. Apply at 60-85°F + low humidity + 2-day dry forecast for best penetration. 200 sqft/gal first coat at 0.80× porosity = 160 sqft effective on PT pine.

Yes — calculator's '10% extra (min 1 gal)' recommendation is the contractor standard. Reasons: (1) touch-up after foot traffic / damage in first year, (2) under-coverage in patches where wood is more porous than expected, (3) future color-match for new boards added 1-2 yr later (paint chemistry shifts year-to-year so matching is hard). Unopened cans last 5-10 yr stored in a basement. The $30-50 extra is cheap insurance against running out mid-project + needing a 2nd trip + lap marks.

DeckOver is a resurfacer — 10× thicker than regular paint. Fills hairline cracks + creates textured surface that hides imperfections. Coverage 75 sqft/gal (vs 200+ for regular paint) is correct — you're putting on much more material per sqft. Same idea: Rust-Oleum Restore at 60 sqft/gal covers cracks up to 1/4″ wide. Both are last-chance products for badly weathered decks where regular paint would peel. Budget 3-4× more product cost than paint, but skip the deck-replacement bill.