The short answer
Small repairs normally do not. Under the Planning Portal's test, a building control application is usually unnecessary if under 25 per cent of the building envelope and under 50 per cent of the roof is touched. Approval does arise for a covering 15 per cent or more heavier, for one with a different fire performance, for chimney breast removal and for a conservatory roof.
The two-part test for re-roofing
The Planning Portal supplies the national measure for re-covering a roof. Two conditions both have to be true before you can skip an application: the work affects under 25 per cent of the whole building envelope, and under 50 per cent of the roof. The envelope is a measure of the external shell, so it counts the walls, floor, roof and every window, door and rooflight together.
Because both limbs apply, a roof can clear one and fail the other. A complete new covering on a small outbuilding might be a tiny part of the envelope while being all of the roof in question.
No council in this part of Hampshire and Surrey publishes a percentage of its own, and Rushmoor and Hart refer readers to the Planning Portal. Some neighbouring authorities word things differently, and each speaks for its own addresses only. Bracknell Forest and Basingstoke and Deane name pitched and flat roof re-covering among alterations that may also need approval. Windsor and Maidenhead's royal borough council mentions re-tiling or re-felting. None says approval is always needed.
Treat the test as a screening tool. For a whole-roof job, a call to your building control body costs little and settles the point.
Weight, fire behaviour and the structure below
Two other triggers apply however small the job. The first is weight: a new covering that adds 15 per cent or more to the roof covering's weight needs approval. The second is fire: approval also applies if the new covering's fire performance would be markedly unlike the old one's.
Weight is where owners tend to be caught out. Going from natural slate to concrete tile, or from a light sheet to a heavy tile, can lift the load beyond the line. The roof timbers were sized for the old covering, so the Planning Portal advises taking professional structural advice before work begins.
Approved Document A expresses the limit a little differently, calling a significant change one where the loading rises by more than 15 per cent. With two phrasings in circulation, a careful roofer treats anything close to 15 as a reason for a structural look.
This is a Building Regulations rule, not a planning one. A heavier covering does not by itself need planning permission, and our guide to planning permission for roof work covers that half of the picture.
Laying back the same sort of covering at about the same weight leaves you outside both triggers.
Chimney breasts, conservatories, windows and flat roofs
Certain jobs sit in a different category and do not depend on the percentages.
Removing a chimney breast is the plainest example. The Planning Portal's position is that regulations approval is always involved, since it is a structural part of the house. A conservatory roof is another: the replacement must meet standards for structure, energy use and ventilation, so a solid roof gets inspected while a simple glazing swap may not.
Roof windows and rooflights carry their own energy figures. A rooflight is held to 2.2 W/m²K, whereas a roof window must reach 1.4 or a Band B rating. The regulations do not treat windows of either kind as part of the roof's thermal element. Cutting a new opening also raises a structural question about the rafters around it.
Flat roofs bring a twist. Part L counts re-covering a flat roof with a fresh membrane as renovation, so the roof is upgraded towards 0.16, with 0.35 as the level that sets the upgrade in motion.
The 2021 edition of Approved Document L governs until 24 March 2027, and the 2026 edition replaces it from that date.
Who signs the work off
Where approval is needed, you pick between the council's building control team and a registered building control approver. Private firms have been allowed to do this for some time, and the register has been a legal requirement since 6 April 2024. In Farnborough the council service is the Hart and Rushmoor partnership, covered in our answer on who handles building control in Farnborough.
The chosen body reviews plans where needed, inspects at agreed points and issues a completion certificate when the work is done. File that certificate with your house papers, because a future buyer's solicitor is likely to ask about it.
The duty to comply rests with the owner, so put three questions to any roofer at the survey: does this job need approval, who will inspect and how many visits should I expect? An answer that approval never matters is not an accurate account of the rules.
We run through these tests when we survey, then give you a single total price on paper. If the job crosses a line you hear about it before booking, not halfway through. The roofing services behind this answer are listed from our homepage.
