The first sign is usually paint. It blisters, then flakes, and underneath the timber has gone grey and spongy where you'd expect it firm. Probe it with a screwdriver and it gives with almost no pressure. Birds or wasps sometimes find their way in through a soft spot before you've noticed the paint at all, and that's often the point homeowners call us.
The symptom is the softening itself — that's the timber failing. The cause is whatever kept it wet for long enough to rot, and that's a separate question worth answering properly before anything gets replaced.
Separating what you see from what caused it
Rot needs sustained moisture, not the odd shower. Fascia and soffit boards sit directly under the gutter and behind the roofline, so anything that keeps water in contact with them for days rather than minutes will eventually cause this. The paint failure you notice first is really the timber telling you it's been wet underneath for months.
Where the rot has reached matters too. Softening confined to the board face near a joint points to one kind of cause; softening running the full length under a gutter run points to another. Look at the pattern before assuming a single explanation covers the whole roofline.
The most likely causes, in order
Long-term gutter overflow is the most common cause we find. A gutter running full or overflowing for years soaks the fascia behind it every time it rains, and paint alone can't keep that out indefinitely.
Unsealed end grain at joints is next — timber absorbs water fastest through its end grain, and a joint that was never primed or sealed rots from that point outward long before the rest of the board shows anything.
Capping old rotten timber with UPVC trim, rather than replacing it, is a cause we see on properties that had previous 'repairs'. The capping hides the problem and traps moisture against timber that was already failing.
Poor ventilation into the roof void plays a supporting role — trapped warm, moist air condensing at the eaves keeps timber damp from the inside as well as the outside.
How to tell the causes apart
A gutter check rules in or out the most common cause quickly — if it's overflowing every time it rains, that's your primary suspect. If the gutter is clear and running well but the rot is localised to one joint, look at the joint detail instead of assuming a gutter fault.
If capping is present anywhere on the run, treat it as suspect regardless of what it looks like from the ground. Capping over rot is designed to look sound, which is exactly why it's a poor repair.
- Check whether the gutter above is overflowing during rain, or has silt and moss built up in it
- Probe the timber at joints first — end-grain rot spreads from a joint, not the middle of a board
- Look underneath any UPVC capping at an inspection point, if you can access it safely from a ladder — do not go onto a roof to do this
- Check the soffit for staining that suggests warm, moist air is condensing against the underside of the roof deck
What a survey should record
A proper eaves survey doesn't stop at noting 'fascia rotten' — it should record where along the run the softening starts and ends, whether it's confined to board faces or has spread into joints and corners, and what condition the fixings and gutter brackets are in once the boards are exposed. Photographs taken with a probe in the timber, showing how far it sinks, are worth more than a written description alone when you're comparing quotes afterwards.
It should also note the ventilation gap at the eaves and whether insulation has been pushed hard against the roof slope nearby, since that's a contributing cause a quote focused only on the visible timber will miss entirely. A survey that only lists 'replace fascia' without any of this detail hasn't actually diagnosed anything — it's priced a guess.
Why this gets worse through winter
Rot doesn't pause between autumn and spring — it accelerates. Colder, wetter months mean gutters run fuller for longer, timber stays saturated for weeks rather than drying between showers, and the fungal decay causing the softening is most active in cool, damp conditions rather than in a dry summer. A board that was merely damp in September can be genuinely soft by February if the same overflow or leak has been running through the wet months in between.
Freeze-thaw cycles make it worse again. Water trapped in already-softened timber expands slightly as it freezes, opening up the fibres further and giving the next lot of rainwater even easier access. That's one reason a fascia that looked marginal in autumn sometimes needs full replacement rather than a patch by the time spring arrives.
Common questions
Can I just repaint the fascia if it's only just starting to flake?+
If you probe the timber and it's still hard, repainting after cutting back to sound timber and priming the end grain properly can buy time. Once the timber gives under light pressure, paint won't stop the rot underneath.
Does fascia rot mean my roof is leaking?+
Not necessarily — fascia rot is usually a gutter or timber detailing problem at the eaves, separate from the roof covering itself. It's worth having both checked at the same time since they're accessed together.
How quickly does eaves rot spread into the roof structure?+
It depends on the moisture source, but sustained wetting at the eaves can migrate into rafter feet over a period of years if left unaddressed. It's not an emergency in most cases, but it shouldn't be ignored for long.
Get a written diagnosis of your eaves detail
We'll check the gutter, the fascia and the ventilation together on one visit from our Biddenden workshop, free of charge, and give you an itemised quote for what's actually needed.