Deck Maintenance in a Wet Climate
A deck in the Northwest rarely dies of old age. It dies of moisture held too long against wood: in board gaps clogged with needles, on the tops of joists, behind a ledger, at the bottom of a post. Most of what keeps a deck sound is keeping water moving, and an hour or two in spring and fall does more than any product. This guide sets out a routine for cedar and composite decks.
Spring
- Sweep the deck and clear every board gap with a putty knife or gap tool. Needles and soil packed in gaps keep both board edges wet.
- Wash. For composite, a manufacturer-approved deck cleaner and a soft brush. For cedar, an oxygen-based cleaner; avoid chlorine bleach, which damages wood fibers. A pressure washer on a wide fan at low pressure can be used on composite with care; on cedar it raises the grain.
- Treat moss and algae in shaded areas with a product appropriate to the material.
- Look for loose boards, popped fasteners and soft spots.
- Push firmly on every railing post. Any movement needs attention.
- Look under the deck: are posts sound at the base? Is water pooling? Is soil piled against wood?
Cedar refinishing
Cedar in this climate needs a penetrating oil finish every two to three years, sooner on the sunniest and most-walked areas. Signs it is time: water no longer beads, the color has greyed, or the surface feels dry and rough.
- Clean and let the deck dry for at least two to three dry days.
- Apply a penetrating semi-transparent oil, not a film-forming stain. Films trap moisture and peel in our weather.
- Work in the shade or on a mild day so the oil soaks in rather than drying on the surface.
- Two thin coats wet-on-wet absorb better than one heavy coat.
Fall
- Clear leaves and needles regularly through the fall; a wet mat of leaves left for weeks stains composite and softens cedar.
- Clean gutters on any covered structure over the deck.
- Move planters onto feet or risers so water does not sit under them.
- Check that downspouts discharge away from the deck footings.
Every few years
- Look at the ledger from below: dark streaks on the siding beneath it, soft wood, or rusted fasteners are warning signs.
- Check stair stringers where they meet the ground.
- Tighten or replace railing hardware.
- Consider a professional inspection, especially for elevated decks or decks older than twenty years.
Composite specifics
- Composite does not need sealing or staining.
- Remove rust spots from metal furniture promptly; use manufacturer-approved cleaners for grease or wine.
- Avoid rubber-backed mats, which trap moisture and can discolor boards.
- Snow can be cleared with a plastic shovel; avoid metal edges and rock salt, which can scratch or leave residue. Calcium chloride ice melt is generally accepted by manufacturers.
Signs that need a builder
- A ledger that is soft, has visible gaps, or shows dark water stains below it.
- Posts that are soft at the base or set directly in soil.
- A deck that sways when people walk on it.
- Railings that move under a firm push.
- Several boards soft in the same area, which often means the joist beneath is soft too.
These are structural issues rather than maintenance. See Deck Repair & Inspection.
Why we build for maintenance
Every Hans deck has joist tape, flashed ledgers, airflow and gap spacing set for our climate because those details make maintenance easier and failures rarer. But a deck in Puget Sound still needs attention, and the owners who give it a few hours a year are the ones whose decks are still sound in twenty-five years.
Not sure what you are looking at under the deck? Send us photos.