The short answer
Fascia boards rot when water reaches them and cannot dry out. The usual sources are an overflowing or leaking gutter, a roof edge that sheds water onto the board, damp air from the loft, and bare timber at the cut ends and joints. Once rot has set in, it spreads along the board and into the rafter ends. The cure is to stop the water first, then cut out and replace the decayed timber.
What the fascia does, and why it suffers
Look up at the bottom edge of any pitched roof. The vertical board you see there is the fascia, nailed to the rafter tips, and it is what the gutter hangs from. The soffit is the horizontal board beneath the overhang. Together the two seal the eaves against rain and nesting birds.
The position is unkind to timber. The board sits at the point where all the roof's water leaves, with a gutter fixed to its face, and it takes sun on one side of the house and driving rain on another. Paint protects it for a time, but a board that stays damp at the back, where nobody can see, decays from the inside long before the face looks bad.
Softwood is especially vulnerable. Its end grain, the cut faces at joints and corners, soaks up water like a straw. A paint film that cracks at a mitre lets moisture in and holds it there.
The causes we see most often
Overflowing gutters. A blocked outlet or a gutter sagging into a dip sends water over the front lip and down the board. Over a season or two that wetting is enough to soften paint and then timber. Our page on why a gutter sags covers the other side of this pairing.
Leaking joints. Each join in a gutter has a seal or gasket, and when it dries out the joint drips onto the same few inches of board. The rot is then local, and it shows as a dark patch under a join or an angle.
Water running behind the gutter. If the bottom course of tiles or slates does not overhang far enough, rain can curl back under the edge and wet the board. A missing or tired eaves tray, the strip of plastic or felt that guides water from under the covering into the gutter, has the same effect.
Damp from inside. Warm, moist air in a poorly ventilated loft condenses on cold timber. Blocked soffit vents and insulation pushed hard against the eaves stop the air moving. Our notes on soffit vents explain why they matter for the boards.
Neglected paint. A board that has gone five or ten winters without attention has little protection left, and exposed ends and screw heads become entry points.
How to tell rot from a paint problem
Flaking paint alone is not rot. Timber that is dry and firm under the flaking only needs rubbing back and repainting. What gives away decay is texture. A board that is spongy, cracks into small cubes, shows dark brown staining or has fungal growth is losing strength.
A screwdriver is the simplest test. Press the tip into the lower edge of the board and at the ends of each length. A sound board resists, while a rotten one gives way and the tip sinks in a few millimetres. Test near the brackets too, since that is where a failing board first lets a gutter drop.
From the ground you can look for sagging at the bottom edge of the board, gaps at the mitres, plant growth in the joints and soffit boards that have bowed or sprung. Wasps or birds using a hole is a sign that the board has already opened up. If bats or nesting birds are present, the work has to wait, since both are protected.
What replacing the boards involves
The gutter comes off first, because the board sits behind it. The old fascia is then removed in lengths, and we inspect the rafter ends behind it. If those are sound, new boards go on. If the ends have rotted, they are cut back and repaired with timber pieces fixed alongside, as the wetting that rotted the board has often reached them as well.
New timber is primed on all faces and ends before fitting, and then painted, so that moisture cannot enter at the cut. Boards can also be made from uPVC, which needs no painting and is quick to fit. The Plastic Centre, a uPVC supplier, puts high-quality uPVC at 20 to 40 years, while MyBuilder says fascia and soffit are replaced every 10 to 20 years depending on material. The gap tells you that quality and exposure both count.
Whether you retain a painted timber board or switch to plastic can depend on the house. On older properties we match materials where the building calls for it, so a period house may be better served by timber. The question of fitting new boards over old ones is a separate one, covered in our answer on fascia capping.
Cost, access and doing it once
Typical UK figures reported by MyBuilder in 2026 are £80 to £150 per metre for fascia and £100 to £180 per metre for soffit, and scaffold is extra at £20 to £40 per square metre. Two-storey houses cost more because of the scaffold. Your fixed price follows from the survey.
If the gutter is tired as well, renewing it in the same visit is sensible, since it has to come off whatever happens. Doing both together avoids paying for scaffold twice. Replacing just a few boards is possible but patchy, and new timber beside tired paint will show.
Whichever route suits the house, the rot will return unless the cause is dealt with. We look at the gutter, the eaves detail and the ventilation as part of the survey, and if water has been running behind the gutter we show you the stained rafter feet and the felt that needs extending. The gutters, soffits and fascias service page lists the rest of the roofline work.
