Short answer
- Clean your deck every year. Use a garden-hose/scrub or a low-pressure wash.
- Pressure-wash only as needed (typically every 1–3 years) to remove grime and gray wood.
- Reseal or restain every 12–36 months depending on product, wood species, sun exposure, and climate.
Typical intervals
- Clear water-repellent: 12–18 months
- Semi-transparent stain: 24–36 months on horizontals, up to 48 months on rails
- Hardwood oils (ipe/teak): 6–12 months
Why this schedule prevents rot
Rot thrives where wood stays damp. Regular cleaning removes mildew and dirt that trap moisture, while a quality sealer or semi-transparent stain blocks water and UV that break down lignin. Keep wood dry, and rot has a hard time getting started. Pay special attention to horizontal surfaces, stair treads, and the first few inches from the house where splash-back and shade keep things wet longer.
Pressure washing: use the right technique
Pressure washers are helpful, but they can shred fibers if you overdo it. Many decks don’t need high pressure—cleaner and brushing often do the heavy lifting.
Recommended specs (wood decking)
- PSI: 500–800 for softwoods (cedar, pine); up to 1,200–1,500 max on tougher woods
- Nozzle: 25° or 40° fan tip
- Standoff: 12–18 inches from the surface
- Wood moisture before sealing: ≤ 15% (use a moisture meter)
- Dry time after washing: 24–48 hours with good airflow
Step-by-step: annual clean and reseal
1) Inspect and prep (30–60 min)
- Tighten fasteners, replace rotten or cracked boards, and confirm proper ledger flashing.
- Sweep debris from gaps; a 5-in-1 tool or putty knife works well. Clear vegetation away from edges.
2) Clean (1–3 hours depending on size)
- Mix an oxygenated deck cleaner (powdered percarbonate) per label in a pump sprayer. Avoid straight chlorine bleach on bare wood—it can damage fibers and corrode fasteners.
- Wet plants and cover delicate landscaping.
- Apply cleaner, keep it wet 10–15 minutes, then scrub with a stiff-bristle deck brush.
- Rinse with a garden hose or a pressure washer on low settings. Work with the grain in long passes.
- For gray or darkened wood, follow with a wood brightener (oxalic acid) to restore color and neutralize cleaners.
3) Dry (24–48 hours)
- Allow full drying. Confirm with a moisture meter ≤15% before sealing. If you don’t have one, wait at least two warm, breezy days.
4) Seal or stain (2–4 hours for ~300 sq ft)
- Choose a penetrating water-repellent or semi-transparent stain with UV inhibitors and mildewcide. Oil-based typically penetrates deeply and enhances grain; water-based tends to dry faster and hold color longer.
- Apply with a stain pad on a pole for boards; use a brush for edges and railings. Back-brush to even out.
- Wipe off any shiny puddles within 10–15 minutes. Thin, even coats last longer than thick coats that film over.
Tools and materials
- Pressure washer with 25°/40° tips (or garden hose with high-flow nozzle)
- Pump sprayer and stiff deck brush
- Oxygenated deck cleaner and wood brightener (oxalic acid)
- Moisture meter (pin type)
- Stain/sealer (1 gallon per 150–300 sq ft, depending on wood and product)
- Stain pad, brushes, roller and tray, painter’s tape, drop cloths
- PPE: safety glasses, hearing protection, gloves, non-slip footwear, respirator or mask when applying chemicals
Approximate costs (300 sq ft deck):
- Pressure washer rental: $40–$80/day (electric units: $150–$300 to purchase)
- Cleaners/brightener: $20–$40
- Semi-transparent stain: $40–$70 per gallon (1–2 gallons typical)
- Misc. supplies/PPE: $20–$40
Safety considerations
- Wear eye protection and non-slip shoes while washing; wet boards get slick fast.
- Never point a pressure wand at skin or near electrical outlets.
- Don’t mix cleaners. Rinse thoroughly between products.
- Protect plants and siding. Rinse metal fasteners and rail brackets to reduce corrosion.
- Avoid ladders with a running pressure washer; use extension wands instead.
Tips for best results
- Choose a mild, overcast day (50–85°F) to avoid lap marks and flash drying.
- Work two boards at a time end-to-end to keep a wet edge.
- On softwood fuzzing after washing, a quick pass with a random-orbit sander (80–100 grit) smooths fibers before sealing.
- Keep rugs and planters off the deck or use risers to allow airflow beneath.
- Test water repellency: sprinkle water. If it soaks in within 10 seconds, it’s time to reseal.
Common mistakes
- Using too much pressure, which raises grain and scars wood.
- Sealing too soon after washing; trapped moisture can cause peeling and mildew.
- Applying thick, shiny coats; film-forming layers on decking tend to flake. Use penetrating products and wipe excess.
- Skipping brightener after alkaline cleaners, leading to dull color and poor adhesion.
- Ignoring details that cause rot: clogged board gaps, unflashed ledger boards, or contact with soil.
Climate and wood differences
- Full sun and hot climates: UV breaks down finishes faster—plan on the short end of the intervals.
- Shady/humid areas: clean more often to control mildew; consider stains with strong mildewcides.
- Hardwoods (ipe, cumaru): avoid aggressive washing; clean and apply a penetrating hardwood oil 1–2 times per year, wipe off all excess.
When to call a pro
- The deck has failing film-forming coatings that need chemical stripping and sanding.
- You see soft spots, suspected rot at posts/ledger, loose railings, or improper flashing at the house connection.
- Multi-story or complex decks where safe access is difficult.
- You prefer spray application and proper containment to protect nearby surfaces.
By sticking to an annual clean, careful pressure washing only as needed, and a 1–3 year sealing cycle tuned to your product and climate, you’ll keep water out of the wood and greatly reduce the chance of rot. A few extra minutes clearing debris and checking flashing each season pays off with a safer, longer-lasting deck.