A grey squirrel can pass through a gap of around 45mm. That figure gets quoted a great deal and it is only half the point.
The other half is that where a gap is nearly big enough, it will simply be made bigger — which is what separates squirrels from every other animal that gets into a roof.
Birds need an opening; squirrels need a weakness
A bird assesses a gap and either fits or does not. A squirrel assesses a gap and, if it is close, spends a few sessions on it. That is why a defect of 20 or 25mm — a gap nobody would think twice about — is a viable entry point on a Kesgrave roof, given a fortnight.
The stages
- A defect appears. A soffit joint opens, mortar cracks at a verge, a board shrinks away from a wall, felt perishes at the eaves
- It is investigated. Squirrels examine roof edges routinely; a gap with air moving through it and a warm space behind is worth a look
- The edge is worked. Repeated short sessions on whichever material is softest at the margin
- It becomes passable. At around 45mm the animal is through
- It keeps growing. Continued daily use and further gnawing enlarge it well beyond what is needed
The practical consequence: there is no safe size of gap. A sound-looking eaves with a 20mm shrinkage gap at one joint is an open roof on a timescale of weeks, and the household will not notice a thing until the noise starts.
Which materials give way fastest
- Perished bitumen felt. Almost no resistance at all — it tears rather than resists
- Softened or rotted timber. The classic, and it is usually rotted from behind by an overflowing gutter
- Loose or cracked mortar. Worked out in pieces
- Thin uPVC and plastic vents. Slower, and entirely achievable
- Sound timber and good mortar. Much slower, and where the animal usually moves on to an easier point instead
What this means for repairs
It is why closing an opening with foam, mastic, timber or netting fails: all four sit inside the range of materials that can be worked. And it is why proofing uses heavy steel mesh, mechanically fixed and dressed in with no exposed edge — the material is outside the range and there is nothing to start on.
It is also the argument for repairing small roof defects as ordinary maintenance. A cracked verge or an open soffit joint is a roofing job worth doing on its own merits, and doing it before anything notices it is a great deal cheaper than doing it afterwards.
Kesgrave's housing
Much of the town is comparatively modern, which changes the details rather than the outcome. Dry-verge units, uPVC fascia and soffit, moulded soffit vents and factory-made junctions all fail in their own way: units lift, joints open with temperature movement, and end caps go missing in a gale. Each of those starts as a gap of a few millimetres.
Questions
How small is too small to worry about?
There is no reliably safe size. A gap of 20mm at a soft material is a viable entry point given a few weeks.
Can they get through an air brick or a soffit vent?
A sound moulded vent generally resists. A broken or missing one is an opening of very nearly the right size.
Why does mesh work when board does not?
Steel is outside the range of materials they can work, and mesh dressed in properly leaves no edge to start on.
Squirrel Control Kesgrave
Squirrel control in Kesgrave is £280 fixed cost. Proofing work, where it is needed afterwards, is £180. Call 01502 630 122 and tell us what you have heard or seen.
For squirrel control in Kesgrave, call 01502 630 122, or read the Kesgrave squirrel control page.