Rotten Fascia Board

What's happening?

The fascia is the board fixed across the rafter ends at the eaves. It closes the roof edge, carries the gutter brackets, and on many houses supports the lower edge of the roof covering. On older UK houses it is painted softwood, and it fails for one reason: it stays wet. Overflowing gutters, leaking joints, gutter set too low so run-off goes behind it, or underlay dressed short so water discharges onto the board rather than into the gutter: all of them keep the timber damp. Wet timber above roughly twenty per cent moisture content becomes available to wet rot fungi, which soften and break down the wood. Once the board is soft the gutter brackets lose their grip, which is why fascia rot and sagging gutters arrive together.

What usually causes it?

• Gutter overflowing or leaking onto the board over a long period
• Roof underlay dressed short so it discharges behind the gutter onto the fascia, keeping the top edge permanently wet
• Paint film cracked or blistered and end grain left unsealed at joints and corners, letting water in behind a coating that then stops it drying out: end grain is where water enters softwood fastest
• Gutter fitted hard against the board with no drainage gap, trapping moisture behind it
• Wet rot fungal decay established in timber held above about twenty per cent moisture content
• Rafter feet decayed behind the board, so the fixings have nothing sound to hold
• Plastic capping fitted over a rotten board rather than replacing it, sealing the decay in to continue

Is it dangerous?

Moderate, and the mechanism matters. The fascia carries the gutter, so a rotten board means a full gutter can pull away and drop, typically over a path or doorway. Structurally, the more serious question is what is behind it: rot that has reached the rafter feet and wall plate is a repair to the roof structure, not a cosmetic board swap. Decay also opens gaps at the eaves that let birds, wasps and rodents into the roof void. Wet rot itself does not spread through masonry the way dry rot can, but persistently wet timber next to it is exactly the condition dry rot needs.

Can I fix it myself?

Assessment is useful and safe from the ground on a single-storey eaves. Look for blistered or flaking paint, dark staining, a wavy or bowed line, moss growing on the board, and gaps opening at joints. Where you can reach safely, press the timber: sound softwood resists, decayed timber gives and may feel spongy or crumble. Photograph the whole eaves line on each elevation. What you should not do is fill and paint over soft timber, or fit plastic capping over it. Both hide active decay that keeps going underneath, and both make the eventual proper repair more expensive because the cover has to come off first.

When should you call a fascia, soffit and guttering installer?

Call within weeks for localised softness with the gutter still holding, and sooner if the gutter is sagging or has pulled away, if you can see daylight or gaps into the roof void, or if birds are getting in. Fix the water source at the same visit: replacing a fascia while the gutter still overflows onto it just restarts the clock. If decay looks widespread along a whole elevation, expect the assessment to cover the rafter feet and wall plate too.

What will the fascia, soffit and guttering installer actually do?

• Remove the gutter and expose the board to establish how far the decay extends, including into the rafter feet and wall plate, separating surface weathering from structural decay and identifying wet rot where present
• Cut out and replace decayed timber, splicing rafter ends where the decay has reached them
• Fit new fascia: replacement timber properly primed and sealed on all faces including end grain, or a full-replacement uPVC board on new sound substrate
• Fix the cause: correct the gutter fall and height, and fit an eaves carrier tray so the underlay discharges into the gutter
• Re-hang the gutter on brackets fixed into sound timber at the correct centres
• Close eaves gaps against birds and rodents while keeping the ventilation path open

Who fixes this

• Fascia and soffit replacement

Questions people ask

Sources & References

1. PCA: Investigation And Control Of Wood-Destroying Insects And Fungi
2. PCA: Wet Rot And Dry Rot Taking Hold In UK Homes
3. TrustMark: Advice For Homeowners
4. HSE: Roof Work