Deck Maintenance: Clean Every Spring, Re-Stain Every 2–5 Yr
The complete maintenance schedule for residential decks — what to do every year, every 3-5 years, and at the 15-year mark. Plus the math behind 'when to replace vs refinish.'
A well-maintained deck lasts 25 years on pressure-treated and 30+ on composite. A neglected deck of either material lasts 10-15 years. The difference is annual cleaning, periodic re-staining (PT only), and small repairs caught early. This guide gives you the year-by-year schedule, the materials for each task, and the trigger conditions for the bigger interventions (board replacement, full re-stain, structural repair).
Annual maintenance (every spring)
Every deck — PT, composite, PVC, hardwood — needs an annual spring cleaning. Best done in April-May once temperatures stabilize.
Cleaning sequence
- Sweep the deck thoroughly — leaves, dirt, debris between boards.
- Inspect for loose screws, popped nails, board damage. Tighten or replace as needed.
- Apply deck cleaner per manufacturer spec. PT/cedar: oxygen-bleach-based cleaner (e.g. Cabot Wood Cleaner, Olympic Premium Deck Cleaner) — $24/gal. Composite: mild detergent + water, soft brush.
- Scrub with a stiff brush (PT/cedar) or soft brush (composite). Pressure washer optional but be careful — too much PSI lifts wood grain.
- Rinse with garden hose. Let dry 24-48 hours before any stain or sealer application.
Hardware check
Walk the deck and verify: railing posts haven't loosened, deck-board screws haven't backed out, joist hangers are tight, ledger flashing is intact. Tighten any loose lag bolts on the ledger to spec (not so tight you crush the wood). Replace any rusted or missing screws.
Re-stain schedule (PT + cedar only)
Pressure-treated and cedar lumber need periodic re-staining or sealing. Composite + PVC don't (do not stain composite). Manufacturer median re-stain intervals:
| Stain finish | Re-stain interval | Manufacturer typical |
|---|---|---|
| Clear sealer | Every 2 years | Thompson's WaterSeal Advanced |
| Transparent stain | Every 2-3 years | Cabot Australian Timber Oil |
| Semi-transparent | Every 3 years | Cabot Gold, Behr Premium Semi |
| Semi-solid | Every 4 years | Olympic Maximum (semi-solid variant) |
| Solid (opaque) | Every 5 years | Behr Premium Solid |
| Penetrating oil (Ipe / hardwood) | Every 1-2 years | Penofin Blue Label |
South-facing decks shorten the interval by ~1 year (more UV exposure). Shaded north-facing decks can extend by 1-2 years.
Water-bead test
The simplest indicator: spray the deck with water. If droplets bead up like on a fresh wax job, the protection is good — wait another season. If water absorbs into the wood within 30 seconds, time to re-stain.
5-year inspection (PT + cedar)
Five years in, do a deeper inspection of structural components. Composite + PVC owners can do a lighter version of this.
- Pull a few decking boards (corners + center) and inspect joist tops for moisture damage. PT joists with visible splits, fungal growth, or sponginess need replacement.
- Check ledger flashing — water entry behind the ledger is the leading cause of deck collapse. If flashing is dry-rotted or aluminum has corroded, replace.
- Inspect post-to-footing connections. Posts sitting directly on concrete (no anchor) wick water and rot at the base — most common reason a 10-year-old deck needs structural repair.
- Verify lateral-load anchors (DTT2Z) are still tight. Re-tighten if loose.
- Photograph everything for your records. Useful when selling the house — documented maintenance increases buyer confidence.
10-15 year decisions
Around year 10-15, you face the bigger questions:
PT decking surface boards (year 12-18)
Surface boards typically need replacement at year 12-18 even with diligent stain maintenance — the wood fibers fatigue and stain stops adhering. Surface-only replacement (boards + screws, framing intact): $18-28/sqft. Cheaper than full deck replacement.
Composite cap fade (year 15-25)
Trex / TimberTech / Fiberon caps will eventually show some fade in extreme exposure. Manufacturer fade warranties cover most fade for the warranty period; document with photos and submit a warranty claim before doing anything.
Railing replacement (year 15+)
Wood railings typically need full replacement at year 15-20; aluminum and composite railings hold longer (25+ years). If the deck framing is sound, replacing just the railing is straightforward.
Mildew + algae management
Damp shaded decks grow mildew + algae over time. Treatment options:
- Wet & Forget — non-bleach mildewcide, spray-on, no scrubbing required, $25/gallon (covers 750 sqft)
- 30 Seconds Outdoor Cleaner — chemical mildewcide, faster acting, harsher on plants. $20/gallon
- Diluted bleach (1:10 with water) — DIY option, but bleach kills surrounding plants, use with caution
- Sodium percarbonate (oxygen bleach) — gentler, plant-safe, slower acting. $30/gallon
Prevention: improve airflow under the deck (no skirt or use slatted skirt), keep gutters clear of overhead trees that drop debris on the deck, trim back any vegetation that touches the deck surface.
UV protection
UV bleaches all decking — PT goes silver-gray, composite caps fade, hardwood goes silver-gray (eventually black-streaked). The USDA Forest Products Laboratory Wood Handbook documents how sunlight and moisture drive this surface weathering in exterior wood.
PT lumber UV management
Stain pigment is your UV barrier. Transparent and clear sealers offer ZERO UV protection (just water repellency). Semi-transparent and solid stains have UV-blocking pigments. If you want long-lasting color, go semi-transparent or darker. If you want natural wood look forever, accept the silver-gray weathering and don't fight it.
Composite UV management
Cap layer has built-in UV inhibitors. Trex 25-yr fade warranty covers normal sun exposure. Premium lines (Trex Transcend Lineage, TimberTech AZEK) hold color noticeably better than mid-tier (Trex Enhance, EDGE Prime+).
Hardwood UV management
Ipe and other tropical hardwoods need penetrating oil annually to maintain color. Skip the oil and they weather to a silver-gray within 6-12 months. Some homeowners prefer the weathered look; others apply oil annually to preserve the rich brown.
Repair playbook
Squeaky / loose board
Likely a loose deck screw. Replace with a longer screw or move the screw to a fresh hole 1" from the original. If the joist itself is rotted (the screw won't bite), the joist needs sistering.
Cracked / split board
PT/cedar: replace the board with new stock. Match the stain color (apply 2 coats to the new board to match the patina). Composite: replace with same brand + line + color. Some manufacturers (Trex Pro Platinum) keep small inventories of common colors for warranty repairs.
Loose railing post
Tighten the post-to-rim-joist carriage bolts. If still loose, the rim joist may have rotted — replace the rim joist section and re-attach the post to fresh framing.
Rotted joist (sistering)
Add a new joist alongside the rotted one (sister joist). Bolt or screw together at 16″ o.c. The new joist carries the load; the rotted joist stays in place because removing it requires pulling decking. Common DIY repair, $50-100 in materials per joist.
Rotted post base
Cut the rotted bottom 6-12" of the post. Set a new post anchor (Simpson PB44 or PB66) on the existing concrete. Install a new post section into the anchor and splice to the existing top with a steel splice bracket. Or replace the entire post. $80-150 in materials.
Frequently asked questions
How often should I stain my deck?
It depends on the finish you used, and the intervals are further apart than most people assume. Clear sealer needs redoing every 2 years, transparent stain every 2-3, semi-transparent — the most popular choice — every 3, semi-solid every 4, and solid opaque every 5. Penetrating oil on Ipe and other tropical hardwoods is the outlier at every 1-2 years. Exposure shifts all of those: a south-facing deck in full sun loses about a year off the interval, and a shaded north-facing deck gains one to two. Rather than working from the calendar, use the water test. Spray the deck and watch: droplets that bead like fresh wax mean the protection is intact and you can wait another season, while water that soaks into the wood within 30 seconds means the finish has stopped working and the deck is due.
Should I pressure wash my deck?
Yes, but at far lower pressure than most people use, because a pressure washer removes wood as easily as it removes dirt. Use 1,200-1,800 PSI on pressure-treated and cedar, and 800-1,200 PSI on composite, which has a polymer cap that higher pressure will strip. Hold the wand 12 to 18 inches from the surface and keep it moving continuously — dwelling in one spot is what raises the grain on wood and burns a visible line into composite. Work along the boards rather than across them. Afterwards, let the deck dry for 24 to 48 hours before applying any finish, because staining over damp wood traps moisture under the coat and causes it to fail within a season. If the deck is only dirty rather than greyed, soap, water and a stiff brush often do the job with none of the risk.
Can I stain composite decking?
No, and attempting it is one of the few maintenance actions that will make a deck permanently worse. Composite boards are wrapped in a polymer cap, and stain cannot penetrate it — the product beads, dries unevenly, peels within months, and leaves a surface that now needs stripping before it can look right again. It also voids the manufacturer's warranty, because the cap is the product. If a composite deck has genuinely faded, the manufacturers sell touch-up products formulated for their own cap chemistry; Trex, TimberTech and Fiberon all support this through their customer service, and fade within the warranty period may be a claim rather than a purchase. For ordinary discolouration, the answer is almost always washing rather than coating: most of what looks like faded composite is organic film sitting on top of it.
How do I get rid of deck mildew?
Treat it, then remove the conditions that grew it, or it returns every year. For treatment, apply a mildewcide — Wet & Forget, 30 Seconds, or sodium percarbonate mixed to the label — leave it to work, scrub with a soft brush, and rinse thoroughly. That handles what is there. The recurrence is a ventilation and debris problem: mildew grows where the surface stays damp, so improve airflow under the deck with a slatted skirt rather than a solid one, clear leaves and debris from between the boards where they hold water, and trim back overhanging trees that keep the surface shaded and drop organic matter onto it. An annual mildewcide treatment as part of the spring clean, usually April or May once temperatures stabilise, prevents most of it from establishing at all.
How long does a pressure-treated deck last?
The surface and the structure age at different rates, and confusing them is what leads to unnecessary rebuilds. Surface boards typically need replacing at year 15 to 18 even with diligent staining, because the wood fibres fatigue and stain stops adhering properly no matter how well it is applied. The framing, if it was flashed and ventilated correctly, lasts 30 to 50 years — so a deck whose boards have failed usually needs a surface-only replacement, keeping the joists, beams and footings in place, at a fraction of the cost of a new deck. Railings sit between the two: wood railings generally need full replacement at year 15 to 20, while aluminium and composite railings hold past 25. The single highest-value habit is the five-year structural inspection, because catching a rotting joist at year five is a $150 repair and finding it at year twelve is a $5,000 framing job.
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