My wood fence has gone gray. Can it be refinished, or does it need replacing?
Short answer
A gray fence can usually be refinished if the posts are solid. Gray is just weathered surface; posts rotted at the ground line are the real end of a fence. Probe the posts, replace the few pickets that are split or soft, then clean with an oxygen bleach, brighten, let it dry, and apply a semi-transparent penetrating oil stain to both sides. If more than a few posts are soft or the fence leans, rebuilding on new posts is the better investment.
Posts decide everything
A fence is only as good as the posts holding it up. Pickets and rails are easy and cheap to replace; posts are set in concrete, carry the whole structure, and rot where the wood meets the ground. Before anything else, walk the fence and push on each post. Then probe it with a screwdriver right at grade and an inch or two below the dirt. Solid wood resists; rot is soft and the tip sinks.
If the posts are sound, refinishing is a good use of a weekend or two. If several posts are soft, or the fence is leaning because the posts have snapped at grade, a new finish is a coat of stain on a fence that is coming down. In that case we would talk about resetting or replacing posts first, and often the old pickets and rails can be reused on new posts.
Repair before refinish
Once the posts pass, deal with the small stuff. Split or cupped pickets get replaced; new redwood or cedar pickets will take stain a little differently than weathered ones for the first season and then blend. Loose pickets get re-fastened with exterior screws rather than nails, which hold better in wood that has shrunk. Sagging rails get new hangers or a cleat. Gates get their hinges checked and a diagonal brace if they have dropped.
This is also the time to deal with soil and plants against the fence. Dirt piled against the bottom rail or pickets holds moisture and rots them from the back. Pull it back a few inches and the fence will last years longer.
Cleaning a fence
The process is the same as for a deck, just vertical. Wet the plants on both sides first and keep them wet. Apply a sodium percarbonate cleaner with a pump sprayer, starting at the bottom and working up so runoff does not streak dry wood, let it dwell, scrub with a stiff brush, and rinse. Follow with an oxalic acid brightener and rinse again. The gray lifts and the redwood or cedar color comes back.
Pressure washing a fence is tempting because there is a lot of it. Keep the pressure low and the tip wide, or you will get the same furry, striped surface you would on a deck, and on thin fence pickets you can blow right through a knot. Treat the washer as a rinsing tool.
Then it dries. A fence dries faster than a deck because air moves on both sides, but a shaded north side in the marine layer season can take several days.
Choosing the stain
For a fence that still shows good grain after cleaning, a semi-transparent penetrating oil stain is our default. It carries enough pigment to block UV, lets the grain show, fades rather than peels, and recoats without stripping. A medium tone lasts longer than a near-clear one.
For rough-sawn fencing, fences built from mixed wood, or fences that have been patched over the years, a solid-color stain gives a uniform look and hides the differences while still wearing rather than peeling in sheets the way paint does.
Whatever you choose, stain both sides. A fence finished on one side cups toward the bare side as it takes on and loses moisture unevenly. If the neighbor's side is their responsibility, at least seal the top edges and end grain, which take the most water.
How long it lasts
In full North County sun a penetrating stain on a fence typically holds its color for a couple of years on the sunny side and longer on the shaded side. The pattern of fading will tell you where the sun hits. A recoat is a clean and a fresh coat, no stripping, and a fence that is recoated on schedule stays protected from the UV and moisture that would otherwise gray it and open the grain again.
Related questions
Can I stain a fence without cleaning it first?
Not well. Stain over gray fibers and dirt sits on the dead surface and wears off quickly, and the color comes out muddy. Cleaning and brightening take a day and make the difference between a finish that lasts and one that does not.
Should I use a sprayer to stain a fence?
A sprayer is fast but it puts stain everywhere, including on the neighbor's car. If you spray, back-brush every section so the stain is worked into the wood, and mask well. A roller and brush is slower and cleaner.
Do fence posts need to be replaced with pressure-treated wood?
Posts in ground contact should be rated for it, which in practice means pressure-treated lumber rated for ground contact, or a steel post. Redwood and cedar heartwood resist rot but do not last as long in wet soil. Setting the post on gravel so water drains away from the end grain helps any post last longer.