Building regulations

Do I need building regulations approval to re-roof?

A full re-roof normally brings building control in; a small patch does not. Below: the test, what tips a job over it, and what a renewed roof must meet.

The short answer

Yes, for a full re-roof. The Planning Portal's guide says a re-roof does not normally call for a building regulations application provided it touches under 25 per cent of the building envelope and under 50 per cent of the roof. Exceed either limit and expect to apply. A new covering 15 per cent or more heavier, or one that would perform significantly differently in a fire, needs approval at any size. Dover district addresses follow a stricter council rule.

5 min read · Part of Roof replacement

A hipped red-tile roof on a white-rendered bungalow — A hipped tiled roof on a bungalow

How the Planning Portal test works

The test has two parts, and a re-roof must pass both to stay outside the rules. The building envelope means every outside surface of the house, taking in the walls and floor along with the roof, and every window, door and rooflight set into them. The second part looks at the roof on its own. On a simple two-slope roof, one full slope is around half the roof, so a job that sounds like a repair can sit right on the line.

Re-roofing under the Planning Portal guide
What the job involves	Application
Under 25 per cent of the envelope and under 50 per cent of the roof	Not normally needed
50 per cent of the roof or more	Expect to apply
New covering 15 per cent or more heavier	Approval needed
Fire performance significantly different	Approval needed

None of the councils we cover sets a percentage of its own. For a Folkestone & Hythe address, the council's building control page lists new roof coverings among the jobs you may need approval for, and points owners to the Portal's interactive house to check theirs. The Portal's re-roofing guide sets the whole test out.

When the new covering weighs more

Weight is the part of the test that applies even to a small area. Approved Document A, the structural guidance, treats a roof loading that rises by more than 15% as a significant change. The Planning Portal words its trigger as a new covering that makes the roof covering 15 per cent or more heavier. Before any work, the Portal's advice is to have a structural engineer or surveyor look at it.

On the survey for a re-roof where the covering changes, we:

record what covers the roof at present and the replacement you are considering
compare the two weights from the makers' data sheets
look at the rafters, the purlins (the beams that hold the rafters mid-span) and the wall plates (the timbers along the wall tops) from the loft
bring in a structural engineer where the new covering is heavier

A covering that would behave significantly differently in a fire needs approval too, whatever it weighs. Our page on changing to heavier roof tiles covers the structural check in more depth.

Insulation once most of the roof is renewed

A re-roof on this scale also brings in Part L, the energy part of the Building Regulations. When more than 50% of the roof surface counts as renovated, para 11.3 of AD L 2021 expects the whole of it to be upgraded to column (b) of Table 4.3. On a flat roof, putting on a new waterproof membrane counts as renovation (para 11.2(d)). A U-value measures how fast heat passes through the roof: the lower the figure, the better.

Table 4.3 gives a roof a threshold of 0.35 W/m²K and an improved value of 0.16 W/m²K; a renovated roof works to the 0.16.
If 0.16 is not achievable technically or functionally, or the payback would run past 15 years, para 4.13 allows the lowest value that passes both tests, and generally no worse than 0.7.
Table 4.2 asks 1.4 W/m²K or WER Band B of a new roof window, and 2.2 W/m²K of a new rooflight.
AD L 2026 takes effect on 24 March 2027 for most work in England, with the tables renumbered 3.2 and 3.3.

HomeBuilding's £10,000 to £15,000 example, a three-bedroom semi with 65 m² of roof covered in plain concrete tiles, already counts insulation alongside labour and scaffolding. Our page on insulation when re-roofing sets out the options.

Who signs the work off near Folkestone

Two kinds of body can sign a re-roof off: the local council's building control service, or a registered building control approver, meaning a private firm listed on the Building Safety Regulator's register. If you go to the council, the team depends on the house:

Hythe, New Romney and Folkestone itself: Folkestone & Hythe Building Control, on 01303 853538.
Dover, Deal and Sandwich: Dover District Council goes further than the Portal, listing new coverings on pitched or flat roofs, "even if this is just like for like", as work needing approval, so for these towns we ask the council before a re-roof.
Canterbury, Whitstable and Herne Bay: STG Building Control Partnership, on 01634 331133.
Ashford and Tenterden: Ashford Borough Council Building Control, on 01233 330282.
Rye and Camber: East Sussex Building Control Partnership, on 01892 602005.

Scaffolding that stands on the pavement needs its own licence. In Kent the fee is £52 per week for 2026 to 2027, with Kent County Council's page leaving the application to the scaffolding company; in Rye and Camber, East Sussex Highways' fee table shows £127 for 28 days. Either way, we arrange the licence with our scaffolder. The roof replacement page shows how a re-roof runs.