The short answer
A small repair, such as swapping a few broken tiles or refixing a ridge, does not normally need Building Regulations approval. Covering a larger part of the roof again is different. The Planning Portal sets its dividing line at 25 per cent of the building envelope and 50 per cent of the roof, and your building control body decides any borderline job.
A repair is not a re-roof
Building Regulations are written around work that changes how a roof performs, so start by naming the job properly before you ask anyone for a view. Putting back a slipped tile, replacing a cracked one, bedding a loose ridge or renewing a length of flashing is maintenance. Afterwards you have the same roof, with the same covering carrying the same load.
Stripping a slope and laying new covering is another kind of job, even when one slope is all that is touched. The covering is a layer of the roof, and under the Building Regulations 2010 fitting or swapping a layer of a thermal element is renovation, and the roof is one of those elements.
Flat roofs follow the same logic. Approved Document L counts a replacement waterproof membrane as renovation, which can raise insulation questions. Table 4.3 gives a 0.35 threshold and an improved value of 0.16 W/(m²·K), so ask before a flat roof is stripped. The build-up decides the answer and no rule of thumb will.
When we survey for roof repairs, we tell you which kind your job is, so you are not left guessing at the paperwork.
The Planning Portal test
For re-roofing, the Planning Portal sets two conditions, and both have to be met before an application becomes unnecessary: under 25 per cent of the building envelope affected, and under 50 per cent of the roof itself. Think of the envelope as the whole outer shell added together, from the ground floor to the rooflights, so the two measures are not the same thing and a roof can pass one and fail the other.
That is the national test, and it is the one to rely on. None of the councils we work with has put a percentage of its own in writing, so be wary of a figure presented as a local rule. The Portal's two conditions also do not collapse into one easy fraction of the roof.
Councils sometimes lean harder. Basingstoke and Deane includes new roof coverings, whether pitched or flat, in the building work that might need approval, so a Basingstoke address merits a call first. That is its wording for its own residents. It stops short of saying every re-roof needs approval, and other councils are not bound by it.
If your job is plainly small, the test is passed and nothing further is needed. Our guide to small roof repairs shows what counts as small.
When a heavier covering changes the answer
Two situations call for approval whatever the percentages say. The first is a replacement that weighs 15 per cent or more above what it replaces. The second is a covering expected to perform very differently if fire reaches it.
Weight is what catches people out. A change of material, such as slate replaced by something denser, can cross 15 per cent. Approved Document A talks about a significant change in loading beyond 15 per cent, so the sensible habit is to ask at 15. The Planning Portal adds that a surveyor or structural engineer should be consulted before the work starts, which is sound advice for any change of material.
This is a Building Regulations and structural question, and it has nothing to do with planning consent. Re-covering a house roof is normally permitted development under Class C, with conditions, while flats, listed homes and conservation areas carry their own rules, which we check address by address.
Like-for-like covering is the easy case, because the weight and the fire behaviour are unchanged. Our guide to repairing or replacing a roof explains when a bigger job earns its cost.
Asking your building control body
When a job sits on the boundary, put the question to your building control body. That may be the local authority team or a registered building control approver, the private alternative that has operated under a registration regime since 6 April 2024. In Test Valley, ask your building control body how it handles your address.
Describe the job in plain terms. Say which slope is involved, what the covering is now, what it will become, and whether the boards or insulation underneath will be lifted. Keep the reply, because a written answer is useful at sale time, when a buyer's solicitor asks what work the roof has had.
Where approval is required, a proper route exists, and a roofer ought to walk you through it rather than skip it. Where it is not required, asking costs you a short phone call.
Our contribution is the survey. We photograph the slopes in question, work out how much of it the job touches, and settle the approval question before anyone climbs up. The answer then sits inside one written price.
