Green, Grey, and Slimy: Wood Fences and Decks Before the First Frost in Delta & Surrey
It is Monday, October 26, 2026, and the fall rains have been sitting on Delta and Surrey wood for weeks. North fence boards have gone green at the soil line. The cedar deck under the maple looks grey when it dries and slick when it is wet. Stair treads feel slimy before they look like a project.
It is Monday, October 26, 2026, and the fall rains have been sitting on Delta and Surrey wood for weeks. North fence boards have gone green at the soil line. The cedar deck under the maple looks grey when it dries and slick when it is wet. Stair treads feel slimy before they look like a project.
Halloween is this Saturday, October 31. Daylight saving time ends next Sunday, November 1, so the walk from the house to the side gate happens in the dark an hour earlier. After that, the next limit is frost. A board that stays wet into a freeze holds water in the grain.
Our early October note on fence and deck moss was written before the rains locked in: clear the film while milder days still help the wood dry. That advice still stands if the boards have not been washed. Yesterday's post on slippery walkways and driveways is concrete, pavers, and the pad you drive on, and it leaves wood alone. Saturday's note on downspout splash streaks is the siding, not the fence. This one stays on wood fences and wood decks: why they go green in these rains, why a soft wash fits the boards better than a driveway blast, how a rental tip marks the grain, and why the useful window is before frost.
Why wood goes green once the fall rains stay
A Pacific front does not rinse algae off a fence. It keeps the surface wet. On a Lower Mainland lot the shady side barely dries between storms: a north fence under maples and cedars, a deck against the house, the stair that never sees the low October sun. A Surrey yard under trees usually shows it first, and a shaded fence in Ladner or Tsawwassen can do the same.
That damp does a few ordinary things to bare wood:
- It feeds a film. Algae, and the thin biofilm that feels like soap, prefer a surface that never quite dries. The green often starts at the soil line, under a planter, and on the face toward the neighbour's cedar, then climbs.
- It holds water against the board. After the sky clears, clean wood can shed a shower. Filmed wood stays dark for hours.
- It makes treads slick. Deck boards, stair treads, and a landing outside a sliding door are where a shoe meets that film. The fence looks tired. The tread is the hazard.
- It is not rot by itself. A green coat is surface growth. Soft, crumbly boards, a rail that moves, or a tread that dips are a repair. A wash does not replace them, and it does not guarantee the next atmospheric river leaves the grain clean.
Wet maple leaves leave tannin, a brown stain in the grain. Cedar needles pack the gap between deck boards and hold moisture there. If a gutter sheets onto the fence, clear that path before you wash, or the next front repaints the line.
Green, grey, and slimy are not the same look
After a shower you are often looking at three things on the same fence.
- Green. Algae and mildew on the shady face and at the soil line. It is brighter after rain and duller on a dry afternoon. That is the film a wash is for.
- Grey. Cedar often silvers as it weathers. An even silver on sunny boards and shady ones is the wood itself, and a wash will not turn that brown. Algae can look grey once it dries. Wet a patch from the grass. Green and slick means film. Even silver that feels like wood is weathering.
- Slimy. That is the film once it is wet, plus moss in checks, on the bottom board, and in the gaps of a deck. Slimy is what your shoe feels. Moss you can see without kneeling is already thick enough to hold water.
Brown rings where a maple leaf sat are tannin, not algae. A fresh ring may fade. An old shadow in the grain can remain, and a cleaning does not guarantee it lifts. Composite and vinyl are not this list. The early October fence note covers those. If the slick spot is concrete, pavers, or the driveway, that is yesterday's walkway post. Leave the high-pressure tip off the wood either way.
Soft wash the wood, and leave the blast on concrete
Wood wants a soft wash. That is low pressure, a cleaner aimed at organic growth, and a controlled rinse. The growth is in the film. Force is what marks the board. A driveway-style blast on wet fall wood usually does four things:
- It fuzzes the grain. The soft early wood between the harder lines washes out, and the board feels hairy after it dries. Cedar that has been damp for weeks does this faster than it did in August.
- It drives water in. Checks, cut end grain, and the gap under a deck board take that water. You do not want it sitting there if the night goes cold.
- It can lift a finish. Paint or stain on a rail, a cap, or a stair stringer is not a patio. High pressure lifts it in patches.
- It leaves the cause. Shade and a gutter that still dumps on the fence feed the film again. A wash treats what is there. It does not move the spout, and it does not guarantee the green stays gone.
Bare concrete beside the deck, a paver landing, and the walk to the gate can take pressure washing. That is the hardscape job. The pressure washing page lists driveways, walkways, decks, patios, house siding, and fences. Name the wood when you book. The tool has to match the surface. Our guide to pressure washing vs soft washing is the longer version of that split, and both methods are booked from that same page.
Rinse plants along the fence so dirty water does not sit in the mulch. Do not pour bleach or a moss killer on the soil line. A slider beside the deck is a window wash, not a pressure tip, and a wash does not repair a failed seal. Stay off a slimy tread, bag the leaves before any water, and keep a tight nozzle out of the gaps between boards. A blast there drives water underneath and can splinter a soft edge. Photos from the grass are enough. Most quotes are provided within 24 hours. A soft wash does not guarantee every tannin shadow lifts.
If a gutter sheets onto the fence, clear it before the wash. A blast does not open a packed trough. Gutter cleaning includes debris removal, a downspout flush, and a look at brackets, sag, and slope. We are fully insured. It does not reattach a pulled spout or replace a split elbow. Clean gutters at least twice a year, once in late fall after the leaves drop and again in early spring. Houses under overhanging trees often need more. A soft board, a crack through, or a loose post is a repair, not a wash.
A simple way to sort the wood
Use the table to sort a typical Delta or Surrey yard. It does not guarantee a board is sound, and it does not cover concrete. The walk and the driveway are the other post.
| What you are looking at | What is going on | Sensible next step |
|---|---|---|
| North cedar fence, green at the soil line | Algae film on bare wood | Soft wash and rinse the bed. A wash does not repair a rotten board. |
| Deck boards or stair treads that feel slimy | Wet biofilm, sometimes moss in the gaps | Soft wash from a dry stance. A blast fuzzes grain. |
| Even silver-grey boards, not slick when wet | Weathered wood, not a film | Leave it. A wash will not turn silver cedar brown. |
| Moss in checks or between deck boards | Moss holding water in the wood | Soft wash the surface. Do not dig with a pinpoint tip. |
| Brown rings where maple leaves sat | Tannin in the grain | Pick the leaves up, then soft wash. An old shadow may remain. |
| A shared townhouse fence or strata deck | Common wood, sometimes under a neighbour's spout | Check the strata rules first. One blast can scar a shared finish. |
Point a downspout extension you already have away from the fence before anyone washes. A wash is not a drainage repair.
Before frost, and before the evenings get darker
The useful window is a mild break with a day for the wood to dry. Inland Surrey lots often see the first frost in November. Lots nearer the water in Ladner and Tsawwassen usually stay milder, though a clear night after a wet week can still freeze. Water left in the grain can freeze and open small checks. Washing the morning after a hard freeze is the worse order. A wash does not guarantee the next night stays above freezing.
Halloween night is October 31, and people at the side gate will use the same treads. If a pumpkin later stains the landing, that cleanup is in our after-Halloween exterior note. Wash the film before the decor sits on it. The clocks fall back on November 1. Cleaning does not add a light. It takes the film off the wood people walk.
If a light cord will cross the deck or run along the fence, wash before the stakes go in. Christmas light installation uses drill-less clips on fascia, eaves, and gutters. Installs run from October 1, crews are normally fully booked by the middle of November, and bookings close December 10, 2026. Details are on the Christmas lighting page. The free 48-hour service guarantee covers a failed light, not a slick tread.
In a dry break, clear loose leaves, clean a gutter that is soaking the fence, soft wash the wood, and pressure wash only the bare concrete beside it. A house starts with residential exterior cleaning. A shared fence goes through our commercial and strata service. We are fully licensed and insured for commercial work. On a common fence, check the rules first.
Quick answers
Will the next rain rinse the green off?
No. A Pacific front adds water. It does not lift algae or moss off wood.
The boards look grey. Is that algae?
Wet a patch from the grass. Green and slick means film. An even silver that still feels like wood is weathering. A wash does not turn weathered cedar brown.
Can I pressure wash the cedar fence this weekend?
Leave the high-pressure tip off the wood. Soft wash fences, decks, and painted rails. Pressure washing belongs on bare concrete beside them. A blast can fuzz the grain and drive water into checks.
Should I wash the day before a frost?
No. Give the wood a mild day to dry. Water left in the grain can freeze and open small checks. If the overnight forecast is at freezing, wait.
Does a wash mean the fence will stay clean all winter?
No. Shade, leaves, and a gutter on the fence line feed the same boards. A cleaning does not guarantee the film stays gone, and it does not repair rot.
Wash the wood before the first frost settles in
Late October in Delta and Surrey is a short gap. The rains are already on the boards, the evenings get shorter on November 1, and the first frost on inland lots often follows in November. Film you can still wipe with a finger is easier to lift than growth that sits wet until spring.
If the north fence has gone green, the deck feels slimy after a shower, or the cedar looks grey and you are not sure which problem it is, tell us what you see and where the house is. We will quote a soft wash for the wood fences and decks, pressure washing only where the surface is bare concrete, and a gutter flush if a spout is soaking the same boards. You can also call 778-652-5906.