Deck Maintenance Guide — Stain, Clean, Repair
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).
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?
Depends on stain type. Clear sealer: every 2 years. Transparent: 2-3 years. Semi-transparent (most popular): every 3 years. Semi-solid: every 4 years. Solid: every 5 years. Penetrating oil on Ipe: every 1-2 years. South-facing decks shorten interval by ~1 year.
Should I pressure wash my deck?
Yes, but carefully. Use the lowest PSI that gets the job done (1,200-1,800 PSI for residential PT/cedar; 800-1,200 PSI for composite). Hold the wand 12-18 inches from the surface and move continuously — pressure-washing in one spot too long lifts wood grain or strips composite cap. Rinse and let dry 24-48 hours before staining.
Can I stain composite decking?
No. Composite has a polymer cap that stain can't penetrate. Stain will bead, peel, and look terrible within months. If your composite has faded, the manufacturer's product line typically includes a touch-up paint specifically formulated for cap restoration. Contact Trex / TimberTech / Fiberon support.
How do I get rid of mildew?
Apply a mildewcide (Wet & Forget, 30 Seconds, sodium percarbonate). Scrub with a soft brush, rinse thoroughly. Improve airflow under the deck (slatted skirt, not solid). Trim back overhead trees that drop debris. Annual mildewcide treatment in spring prevents most problems.
What's the lifespan of pressure-treated decking?
15-25 years for the surface boards (typical replacement at year 15-18 even with good maintenance). 30-50 years for the framing if properly flashed and ventilated. Surface-only replacement at $18-28/sqft is common at the 15-year mark; full deck replacement is rare unless framing fails.
When should I replace my deck?
Replace surface boards: when stain stops adhering or boards show structural cracks (typically year 12-18 for PT). Replace framing: when joists show rot, ledger has water damage, or post bases have rotted (typically year 25+ if maintained, year 15 if neglected). Full deck replacement: when both surface and framing are at end-of-life.
Do I need to seal cut ends of pressure-treated lumber?
Yes — IRC R317.1.1 requires it. PT treatment penetrates only the outer 1/4-1/2" of the lumber; the core is untreated. Cut ends expose the untreated core to moisture and rot. Apply PT-grade end-cut treatment (copper-based, Quick-Cut, Wood Defender) to all cut ends. Required by code, prevents premature failure.
How do I fix a squeaky deck board?
Pull the deck screw, drill a fresh hole 1" from the original (predrill if PT to avoid splitting), install a longer screw (#10 × 3" instead of standard #8 × 2-1/2"). If still squeaky, the joist beneath is moving — sistering a new joist alongside the squeaky one solves the problem permanently.
What's the best way to clean a composite deck?
Mild detergent + warm water + soft brush. Rinse with garden hose. Avoid: pressure washer above 1,200 PSI (damages cap), bleach (voids most warranties), wire brushes (scratches cap). Trex sells composite-specific cleaners for stubborn stains; they cost $15-25 a bottle.
Should I refinish my deck or replace the boards?
Decision tree: (1) Are 75%+ of boards structurally sound? Refinish if yes, replace surface if no. (2) Is the framing intact? Refinish if yes, full replacement if no. (3) Are you staying 5+ more years? Refinishing makes sense; replacement makes more sense if you'll be in the home 10+ more years and you've already done one refinish cycle.