How to Seal a Cedar Fence

“Sealing” gets used for three different products that do three different jobs, and the cedar aisle does not help by labelling nearly everything a sealer. Start from what you want the fence to look like in two years.

The trap is the clear product. It beads water beautifully the week it goes on, which feels like protection, but cedar goes grey because of sunlight, not water, and a clear finish lets the sunlight through. If keeping the colour is the point, you want pigment — a toner if you want the grain to show almost unchanged, a semi-transparent stain if you want a little more colour and a lot more life.

Whether finishing is worth it at all, and why cedar is different from pressure-treated pine, is covered in should you stain your fence→.

A fence board gets wet from every direction and moves with every season. A finish that forms a film on top — paint, solid stain, varnish-type “sealers” — cracks as the wood moves, lets water in behind it and peels. Once it peels it has to be scraped or stripped before anything else will stick.

A penetrating finish soaks into the wood and wears away from the surface gradually. When it fades you clean the fence and apply another coat straight over it. Oil-based versions soak deepest and cope well with cedar's natural extractives; water-based penetrating stains dry faster and resist mildew in humid climates, and are a sound choice when the label says they are suitable for cedar.

New cedar arrives in two states, and they are ready at very different times.

• Kiln-dried, smooth-planed boards: often ready in a few weeks, but planing leaves a hard, polished “mill glaze” that stain cannot get through. Scuff it off first.
• Air-dried or green rough-sawn boards: one to several months, longer in a wet season or a shaded yard.

The calendar is only a guide. Sprinkle water on a few boards, including on the shaded side: if it darkens and soaks in within a minute, the wood will take a finish; if it beads, it will not, and whatever you apply will sit on the surface and fail early.

Weather matters as much as the wood: 50 to 90°F, dry boards, no rain for 24 to 48 hours, and out of direct midday sun so the product soaks in before it skins over. Spring and early autumn are the seasons for it.

Most sealing guides are written for any wood. Cedar has a handful of behaviours of its own, and they account for most of the “the sealer didn't work” stories.

1. Clean the fence

Even a new fence carries dust, pollen and handling marks, and an older one has grey fibre and mildew. Oxygen bleach and a stiff synthetic brush do it without a pressure washer — the full method, and which cleaner matches which stain, is in how to clean a wood fence→. Never use a wire brush on cedar: the steel left in the grain rusts into black specks.

2. Brighten

An oxalic acid wood brightener, applied to the damp wood after cleaning and rinsed off, restores the warm colour, removes iron streaks, and neutralises the alkaline cleaner so the finish absorbs evenly. On smooth new boards it also helps open up mill glaze.

3. Let it dry, then test

At least 48 hours of dry weather, then the water-drop test on the shaded side.

4. Protect what should not be stained

Cover plants, the lawn edge, a painted house wall or a neighbour's car. Oil-based stain overspray travels further than it seems and is hard to remove from siding and concrete.

5. Apply one saturating coat — spray, then back-brush

Work one section at a time. Start with the top rail, post tops and board ends, because end grain soaks up water fastest and needs the most protection. Then spray the face of the boards from the top down with a pump sprayer and immediately work it in with a brush along the grain. The brush pushes product into the wood and evens out drips and lap marks; spraying alone leaves a thin, uneven film.

Keep a wet edge — stop at a post or board edge, not in the middle of a board — so sections do not overlap into darker stripes. On very thirsty rough-sawn cedar, some products call for a second application wet-on-wet, before the first has dried; follow the label, and never add a coat once the first has dried.

6. Wipe off what does not soak in

After about 20 to 30 minutes, go back over the section with a rag or a dry brush and remove any product still sitting glossy on the surface. Unabsorbed stain stays tacky, collects dirt and peels. Oil-soaked rags can heat up and ignite as they dry: lay them flat outdoors or keep them in a sealed metal can of water.

7. Do both sides if you can

A board finished on one face and bare on the other takes up and loses moisture unevenly and tends to cup. On a privacy fence it is often only practical to do your side, which is fine; on a horizontal fence or a picket fence, doing both is worth the effort.

A 6-foot privacy fence has about 6 square feet of face per linear foot, per side. Coverage depends mostly on the surface: rough-sawn cedar drinks product, typically 150 to 250 square feet per gallon, while smooth boards run closer to 250 to 350.

Add roughly 10–15% for posts, rails, board edges and the first time a dry fence soaks up more than expected. Double the figures for both sides. Label coverage on the can is usually quoted for smooth wood. The fence stain calculator→ adds those allowances for you.

A penetrating stain on cedar typically needs another coat every 2 to 4 years — sooner on south- and west-facing runs, later in shade. A clear water repellent needs it every 1 to 2 years. The fence tells you better than the calendar: when water stops beading on the surface and the colour has faded noticeably, clean it lightly and recoat. Staying on that cycle means you never have to strip it.

Keep to the same type of product when you recoat. Water-based and oil-based penetrating finishes do not always bond well over each other, and switching usually means stripping back to bare wood.

Doing it yourself, a quality penetrating stain runs roughly $30 to $60 a gallon, so a 100-foot privacy fence costs about $100 to $250 in product for one side, plus cleaner, brightener and a pump sprayer. Professionally, expect around $3 to $8 per linear foot for one side of a 6-foot privacy fence, with cleaning included.

Over the life of a cedar fence those recoats add up, and they are part of the honest comparison with low-maintenance materials — see cedar vs pressure-treated→ and how long a fence lasts→. If you are still pricing the fence itself, wood fence cost→ has the per-foot numbers.