A rotten fascia is one of the commonest faults on a house with timber boards, and one of the easiest to overlook, because the board sits at the top of the wall, under the gutter, where nobody looks. By the time the paint is peeling in sheets or a section of board has dropped, the rot has usually been working for several winters. Wet rot is a fungal decay that takes hold in timber that stays damp, and it spreads for as long as the damp supply continues. The board itself is cheap. The harm lies in what it protects, which is the ends of the rafters, the wall below and the fixing for your gutters. This guide shows how to recognise rot, how it starts, what it puts at risk and how it is put right.
How to recognise a rotten fascia
Look from the ground first, ideally in good light and with binoculars if the eaves are high. Peeling or blistered paint, dark staining along the lower edge, green algae on the underside, and joints where the board has opened up are early signs. Look for a board that has bowed outwards, a gap between the fascia and the gutter, or a gutter that has begun to droop because its brackets no longer hold. On uPVC, which cannot rot, the signs are in the board behind: a plastic cover that has come away at one end, or one that rattles in the wind.
Close up, the simplest test is a screwdriver or a thin blade. Press the tip into the board at the joints, at the corners, behind the line of the gutter and along the bottom edge. Sound timber is hard and resists. Wet rot is soft, spongy or crumbly, and the blade sinks in or lifts out flakes. Dry fibres that tear away in long strands are another sign. Our guide to the signs your gutters need replacing includes the symptoms that show up along the gutter line, which often come first.
What causes fascia rot
The cause is nearly always water in the wrong place for too long. The common routes are these:
- A gutter that overflows because it is blocked, undersized or has sagged, spilling water over the board.
- A leaking joint that drips onto the face or the top edge of the fascia.
- A gutter fixed so close to the board that water runs behind it and down the back of the timber.
- Felt at the eaves that stops short of the gutter, so water that runs down under the tiles soaks the top of the board.
- A paint film that has failed, letting rain into bare timber, particularly at the end grain where boards are cut.
- Cut ends and joints that were never sealed when the board was fitted.
Often it is two or three at once. A gutter blocked by moss washed from the roof, a joint that weeps, and a coat of paint that was last done well before the last owner moved in is typical. Our answer on why gutters overflow and the page on leaking gutter joints deal with two of the usual culprits.
Why a rotten fascia is more than a cosmetic problem
A fascia does three things. It closes the gap under the lowest tiles, it carries the gutter and it stiffens the ends of the rafters. When it rots, each of those jobs fails in turn.
First, the gutter. Brackets are fixed into the board, and rotten timber will not hold a screw. The gutter drops, water ponds in the trough and runs over the front, which wets the board further. That is a cycle that gets worse in every wet spell.
Second, the roof edge. With a rotten board, the gap beneath the tiles opens, which lets in wind, rain, birds and insects. Wasps and squirrels use broken eaves as a way into the loft, and nests there can be difficult to move. The felt, if exposed, is damaged by sunlight and starts to fail.
Third, and most seriously, the rafter ends. The fascia is nailed to the ends of the rafters, and anything that wets the board can wet them. Rafters that rot lose strength where they bear on the wall plate and carry the roof's weight, and this is the point where a cheap job becomes a structural one. Repair at this stage costs far more than catching the board early. Our guide to fascia capping and replacement explains why putting plastic over a rotten board makes this worse.
What is behind the board
You cannot tell from outside how far rot has gone. A board may look reasonable from the ground and be crumbling at the back. Rot may have run along a rafter end for a hand's length behind a sound-looking section of fascia. And the wall plate, the horizontal timber at the top of the wall on which the rafters sit, can be damp where the felt has failed.
When the old fascia is off, we look at each rafter end. Sound ones are left. Soft ones are cut back to good timber and a new piece is spliced in alongside, fixed to the sound rafter so the load passes through it. Damp but sound timber is dried, treated and left to dry before the new boards are fixed, because covering wet wood simply starts the process again. If the damp is widespread, we explain what it means for the roof and quote the repair separately, with photographs.
Can a rotten fascia be repaired, or must it be replaced?
It depends on how much of the board is affected and where. A small area of rot, say at one joint or at the end of a board near a downpipe, can sometimes be cut out and a new section let in, with the surrounding timber treated and primed. Filler is useful for dents and small damage, but it is not a repair for soft timber. A board that is rotten along a length, soft at the joints or rotten at the back where you cannot see it, is better replaced, as the cost of repeated patching adds up to more than a new board.
Replacement allows a decision about materials. Timber is traditional and suits a period house, a listed building or a conservation area, but needs regular painting. uPVC does not rot or need paint, and it is the usual choice. Our page on how long uPVC fascias last sets out what to expect. If your house is in a conservation area, ask the council's planning team whether a change of material needs consent before you order anything.
Soffits, bargeboards and the rest of the roofline
Where the fascia is rotten, the soffit beside it is often damp too, because the same water reaches both. Soffit boards sag, stain and crack, and the loft above may be starved of air or open to birds. Bargeboards, the boards along the gable ends, rot for similar reasons, usually from the top, where the tiles overhang and water is directed onto the timber. If one part is failing, check the rest. A full roofline replacement deals with all of it in one visit, and the page on what happens during a roofline replacement explains the order of work.
Before any soffit is disturbed on an older house, it is worth knowing whether it could be asbestos insulating board, which some houses built before the year 2000 have. Our answer to whether your soffits could contain asbestos explains the position, and why nobody should drill or break a suspect board.
Stopping it happening again
Replacing a rotten board without fixing the cause is the commonest reason it rots again. A new board needs a gutter that falls to the outlet, joints that stay sealed, a felt that runs into the trough, and cut ends sealed with primer before fixing. After that, the board is protected by keeping the gutter clear. Our gutter maintenance guide sets out an easy yearly routine. Moss on the roof tiles sheds into the gutters and blocks them, so a roof that sheds moss every year has a cause up on the tiles that wants treating as well.
Mistakes that let rot come back
Three habits turn up again and again on boards that have rotted twice. The first is painting over damp or flaking timber without cutting back to sound wood, which seals the water in. The second is fixing a new board tight against an old, wet rafter end, which hands the rot straight to the replacement. The third is leaving the cut end of a new board bare. End grain drinks water faster than any other face, and a brush of primer or preservative on every cut end before fixing costs almost nothing. Where timber boards are chosen, a primer, an undercoat and a gloss or microporous finish give a long life, provided the first coat goes on before the board is fixed.
What it costs
A single repaired section is a modest sum, and a full roofline is a larger one. If the whole roofline is going, a published UK guide gives a typical range for a uPVC job on a three-bedroom semi that tops out at £3,500 and starts at £1,800, with a detached house running from £3,000 to £6,000. A good part of that is scaffold. Treat them as typical UK ranges, nothing more. Your fixed quote follows the survey, once the boards have been tested. Our page on what soffits and fascias cost sets out the factors.
What we do on a survey
We test the boards, trace the water back to its source, check the felt at the eaves where it can be seen and photograph what we find. The report states whether a repair will do or the boards should be replaced, and why. Where timber is sound we say so, even if it is ugly, and where it is not, you see the soft board in the picture. The price is set in writing before work starts, and the job is covered by our ten-year workmanship guarantee. For the full range of roofline work, see guttering, soffits and fascias. Call 01256 213956 if you would like the boards looked at.
