The short answer
If birds are using a gap in a soffit, the safest course is to leave an active nest alone until the young have gone, then close the gap. Section 1 of the Wildlife and Countryside Act 1981 is aimed at a person who intentionally damages an occupied nest or one still being built. Bats are protected separately, so check before sealing any opening.
Why birds use soffits
A soffit is the panel under the roof overhang, closing off the eaves from below. Where it has split, come loose, rotted at an edge or been left with a gap behind the fascia, it forms a sheltered cavity that birds find attractive. Starlings, sparrows and others slip into the roof edge and build inside.
The nests themselves do not cause leaks, but the habit does. Nesting material, droppings and feathers can block the ventilation of the roof space, trap damp against timber and attract insects. Birds pulling at a damaged board can widen the gap, and a nest sited next to wiring or insulation adds a small fire risk and dirt.
The first question is whether the gap should exist at all. Some soffits carry vents so that air can flow into the roof void, and Ventilation at the eaves is deliberate: under BS 5250:2021 and Marley's advice, a cold roof with HR underlay needs 25 mm along the eaves at 15 degrees or less and 10 mm on steeper roofs. A designed vent should carry a mesh that lets air pass while keeping birds out.
A gap that is not a designed vent, such as a split board or a missing section of soffit, is a defect. It lets weather, birds and pests in, and it should be mended.
What the law says about nests
Wild birds are protected by the Wildlife and Countryside Act 1981. Section 1(1) applies only to a nest with birds using it or building it, and it turns on the word intentionally: an owner who does not know of a nest stands differently from one who knowingly clears it.
GOV.UK's bird guidance makes clear that building and repair work is not among the purposes for which a licence is given, so the practical conclusion is to wait.
Check before you start. Look for birds going in and out, listen for chirping from the gap, and watch for a few days. If a nest is in use, work on that part of the roof waits until the young have flown and the nest is no longer active.
We do not give dates for a nesting season, because it varies by species and by year. The test is whether a nest is in use or being built, not the calendar.
This is general information. If you are unsure, ask a roofer to check the gap before work begins, and seek advice from a wildlife organisation if needed.
Bats are a separate question
A gap that looks like a bird's way in could also be used by bats. Bats are protected more strictly, and they roost in small gaps at the roof edge, behind fascias and in soffit boxes. Roosts are used by day and may be empty at times, so an empty-looking gap proves nothing.
The law is in two parts. Two provisions apply. Regulation 43(1) of the Habitats Regulations 2017 covers deliberate disturbance and harm to a breeding or resting place, and damage to a roost needs no intent. Section 9(4) of the 1981 Act also catches a person who, intentionally or recklessly, disturbs a roosting bat or blocks its way in.
The GOV.UK guidance on bats names roof repair or replacement as an activity that can affect them, and roosts are fully protected, so sealing a gap that bats use is the kind of act that matters.
If you see droppings below the gap, bats flying out at dusk, or staining at the edge of an opening, stop and seek advice before closing it. An ecologist or the relevant statutory adviser can say what is allowed. A licence is not always needed, but the check is never skipped.
Closing the gap once the nest is empty
Once the nest is finished with, and bats have been ruled out, the repair can go ahead. Old nest material is bagged, the area is cleaned and rotten board is cut out. A new soffit section is fitted, secured at the edges and sealed.
Where airflow is needed, a proper vent with fine mesh lets air through but not birds and wasps. Foam stuffed into a gap traps moisture, blocks airflow and gets torn out by birds.
Check what else is wrong. A soffit that has split may point to a fascia that has rotted or a gutter that has leaked onto it. Our page on what soffits are explains the parts, and the gutters, soffits and fascias hub covers the whole roofline.
One caution on older properties: the HSE says external soffits can contain asbestos insulating board, so an old soffit should not be drilled or broken before it has been checked.
Our survey photographs the gap and the board. Where birds are active we advise waiting, and where bats are possible we advise a check first. The repair itself comes as a single total in writing.
