What Is Eaves Felt Rot and the Eaves Tray Fix?

Underlay is the waterproof sheet laid over the rafters beneath the battens and tiles. It catches any water that slips past the covering and carries it down the slope. At the bottom, it has to finish by leading that water into the gutter.

Why does the felt at the edge fail first?

It is the most exposed part. The felt hangs over the edge of the roof and slumps between the rafters, forming a shallow dip where water sits instead of draining. Sun and weather work on the exposed strip, and nothing underneath holds it up. Over decades the felt dries out, goes brittle and splits, or sags until it dips behind the fascia instead of over the gutter.

Older felt is the usual culprit. Modern underlays handle this better, but a roof laid long ago relied on bitumen felt that has simply run out of life. A roof can be sound everywhere else and still have rotten felt along the bottom edge.

The fascia board hides the problem, which is why it often goes unnoticed until the damage is well advanced.

When felt fails, the water does not simply drip into the gutter. It runs behind the board.

What are the signs of eaves felt rot?

From the ground, look for a fascia board that is stained, dark along its top edge or peeling in patches. A gutter that fills with grit or a tile that has dropped near the eaves can also be a clue. The rafter ends behind the board stay damp, and damp timber softens. In the worst cases you find the ends of the rafters spongy when a roofer lifts the board.

Indoors, a damp mark where the ceiling meets the outside wall, or a stain on the soffit above a window, can point to the same cause. The water arrives at the wall plate, the timber that sits along the top of the wall, and not through the loft, so the loft itself may look perfectly dry. That is what makes this fault easy to miss on an inspection that only looks inside.

Damp at the roof edge also feeds the algae and rot on timber soffits. Our answer on green or black soffits covers what the staining means.

An eaves support tray is a rigid strip, usually plastic, that is fixed along the bottom of the rafters. The underlay is laid over it, so the felt runs out and down into the gutter in a straight, supported line instead of slumping.

How is an eaves tray fitted?

The gutter and the fascia come off first so the edge is open. The roofer cuts out the failed felt back to sound material, repairs any rotten timber, and fixes the tray to the rafter ends. New underlay is lapped over it, and the lowest tiles or slates are laid or refixed on top. The fascia and gutter then go back on.

The tray stops the underlay sagging, so the water discharges into the gutter. It is a small, cheap component for the job it does, and it is the reason a good eaves repair lasts. It also tells you a lot about the standard of a roofer: ask whether trays are part of the plan.

Where the roof is old, doing the edge on its own can be false economy; our page on fascias with a new roof explains when to combine jobs.

The eaves are also where a cold roof breathes. BS 5250 deals with moisture in buildings, and it matters here because the roof void needs air movement. Where a non-breathable HR underlay is used, Marley gives 25mm of ventilation along the eaves for pitches of 15 degrees or less, and 10mm for anything steeper.

Does the tray block the ventilation?

It should not. Eaves trays come with a vented section, or the soffit is fitted with vents or a ventilated board, so airflow is kept. An eaves fix that seals the edge solid can create condensation in the loft, so the airflow is checked as part of the job rather than guessed.

HR underlay is non-breathable, so it needs those gaps. A breather underlay behaves differently, and the right answer depends on what the roof already has. We tell you which in the survey, with photos of the edge, and give one written price afterwards. If you have staining or sagging at the eaves, ask us to check it. See the full gutters, soffits and fascias page for the rest of the roofline.