Why your cedar fence turned gray (or black), and whether it can come back

Published September 28, 2026 · 6 min read

Almost always it is sunlight rather than rot, and almost always it comes back. Gray on a cedar fence is a thin layer of dead surface fiber that ultraviolet light has bleached: roughly a sixteenth of an inch of oxidized cellulose sitting on top of wood that is still the same tan cedar that went up. Black is a different problem, and it is usually mildew growing where the wood stays damp. Rust-colored streaks are a third thing again. The pattern on your fence tells you which one you have, and which one you have decides what the fence needs before it can be stained.

Four things discolor cedar, and they do not look alike

1. UV graying: silver, even, worst where the sun lands

This is the common one. Cedar gets its color from lignin and the extractives in the wood, sunlight breaks the lignin down at the surface, rain rinses the loosened fiber off, and what is left is a felt-gray mat of cellulose. It shows up first on the runs that take afternoon sun and on the top third of every picket, because that is what the sky sees. It is even: no blotches, no edges, just a fence that has gone from tan to silver over two or three summers.

The quick confirmation: scrape a gray picket with a fingernail or the corner of a putty knife. If tan wood appears under the scratch, the gray is surface only, which is the answer you want.

2. Mildew: black or green, blotchy, in the damp corners

Mildew is a growth, so it shows up where water sits rather than where sun hits, which is the opposite pattern from graying. Look at the bottom two feet, the north side, the run behind the shed, and anywhere a sprinkler head reaches. It reads as black speckling that runs together into patches, sometimes with a green cast on the shaded side. Unlike graying it has edges, and it looks worse after a wet week.

It also does not scrape off to tan the way gray does, because it is sitting in the fiber rather than being the fiber. A cleaner kills it; a stain sprayed over it just seals it in and the fence looks dirty from the day it dries.

3. Tannin bleed: dark brown streaks under knots and nail heads

Cedar carries natural tannins, and water moving through the wood carries them to the surface and leaves them there. You see it as brown or near-black streaks running downward from knots, from the top rail, and from the heads of the nails or screws. On a new fence it can show up in the first rainy season and it surprises people, because the fence is too young to be gray and it already looks stained.

Tannin bleed is cosmetic and it responds well to a brightener, which is exactly the chemistry it was made for. Streaks running from fasteners specifically can mean the fasteners are corroding, which is worth a look before the stain goes on.

4. Iron and well-water staining: orange, in a sprinkler pattern

If the streaks are orange or rust-red and they fan across the boards in an arc, look at your irrigation. Water with iron in it leaves that behind every time the head runs, and the shape on the fence is the shape of the spray. Around Austin it turns up most on properties on well water, and it is worst on the run nearest the head.

Oxalic acid takes iron staining out of wood, so the fix and the fix for gray are the same chemical step. What matters more is that the head gets turned or swapped first, because the stain goes back on within weeks otherwise, and the constant wetting at the bottom rail is doing more damage than the color suggests.

A five-minute check before you call anyone

1. Scratch test. Scrape a gray board. Tan underneath means surface graying. If the wood is gray a layer down, or fibrous and soft, that board has more going on.
2. Where is it worst? Worst in the sun means UV. Worst in the shade and at the bottom means mildew. Worst below knots and fasteners means tannin. Worst in an arc means the sprinkler.
3. Thumbnail the bottom rail and the picket bottoms. If a thumbnail sinks in, that is rot, and no amount of color work fixes it. Those pieces get swapped.
4. Push the fence. If it moves at the posts, the posts are the first conversation and the color is the second.

Most fences come back with one obvious answer and one secondary one, usually gray everywhere plus black at the bottom on the sprinkler side. That combination is the ordinary case.

What the brightener step actually does

Restoration is two chemicals doing two different jobs, and people tend to hear them as one wash.

The first is a wood cleaner, typically sodium percarbonate, which is alkaline. Left on the wood long enough to work, it lifts the dead gray fiber loose and kills mildew. It also darkens the wood and leaves it looking slightly muddy, which is why a fence halfway through this process looks worse than it did before anyone touched it.

The second is the brightener, an oxalic acid solution. It neutralizes the alkaline cleaner so the surface is back to a pH stain can live on, and it pulls the tan tone back out of the wood, taking tannin streaks and iron staining with it. This is the step that turns a gray fence cedar-colored again before any stain has gone on, and it is the one homeowners skip when they do this themselves. A fence washed and not brightened will take stain unevenly and the color reads flat.

Then it dries, at least 48 hours and longer after rain, because stain does not penetrate wet wood. We run this as two visits for that reason. The full sequence is on the fence restoration page, including where picket swaps fit in.

What restoration gets back, and what it does not

It gets back color and surface. A gray fence with sound posts and mostly sound pickets comes back to cedar tan and then holds a stain for the same 2 to 3 years a newer fence would, which is the whole point: the protection is worth more than the color.

It does not get back rot. Soft wood at the bottom of pickets and rails is gone, and those pieces get replaced before staining rather than painted over. It does not close checking either. The long splits that open along the grain as cedar ages are permanent; stain seals them against water and makes them much less obvious from across the yard, but they stay. Cupped and curled pickets stay cupped. A leaning post stays leaning.

A fence that is ugly but solid is worth restoring every time. The line is roughly when a quarter or more of the pickets are soft, the bottom rails have gone on most panels, or several posts move at grade. That is good stain on bad wood, and we would rather say so from the photos than take the job.

The cheapest version of this problem is the one you catch early

A fence that is one or two summers old and just starting to silver along the top edge does not need any of the above. It gets stained, in the lower half of our range, and the gray never arrives. A fence that has been bare for five years needs the cleaning day, the brightener, the drying time and more stain, because opened grain drinks it, so it sits toward the upper half instead.

That gap is why we push first-cycle staining hardest in the newer, shadeless subdivisions east of town. On an open lot in Manor or east Pflugerville there is no north run under an oak buying an extra year, so a builder fence grays on all four sides at once. The flip side is that a fence like that also restores evenly and re-coats as one job.

Not sure which of the four you are looking at? Send a photo of the worst run through the quote form and we will tell you what caused it, whether it needs a brightener, and what it costs, free and by text.

Related: Austin fence restoration · Manor