The short answer
Not as a single figure. According to the Planning Portal, you normally need no building control application for a re-roof if less than 25 per cent of the total building envelope is affected and less than 50 per cent of the roof is affected. Both limits apply together, and a heavier covering or different fire performance changes the answer, so confirm the position with your building control body.
Two limits, read together
The Planning Portal gives two tests, and a re-roof normally avoids a building control application only if it passes both. First, less than 25 per cent of the total building envelope is touched. Second, less than 50 per cent of the roof is touched.
Envelope takes in every surface that encloses the building: the floor, the walls, the windows and door, and the roof together with any roof windows or rooflights. A quarter of the whole envelope is therefore a far bigger area than a quarter of the roof alone, which is why the single figure misleads. The roof limit is a separate test with its own measure.
Because the conditions are joined by "and", passing one is not enough. A job comfortably inside the envelope limit can still be too large a share of the roof. Equally, any shorthand that quotes only one of the two figures misstates the national position.
On our surveys we measure the slopes and photograph them, so the area worked on is written down before anyone talks about thresholds. That record is also useful if your building control body asks for it. A written note of both percentages kept with your quote saves a debate later.
When the new covering changes the answer
Area is not the only test. The Planning Portal also asks for approval when the new material is at least 15 per cent heavier than what it replaces, or when it will behave significantly differently in a fire. Fire performance means how the covering responds if flames reach the roof, so a product with a different rating from the old one is a reason to ask first. Approved Document A words the weight point a little differently, calling a loading increase significant when it is more than 15 per cent, so name whichever document you rely on.
This is a Building Regulations matter, not a planning one, and the two get confused often. Where the weight will change, the Planning Portal advises consulting a structural engineer or surveyor first.
Any change of covering material is worth checking against that weight test. Our page on heavier roof tiles explains how the structure carries the load, and the guide to the best roof covering for a re-roof compares the options. The main roof replacement page shows how the whole job runs.
What the councils around Andover say
None of the councils around us gives a percentage figure, so nobody should quote one as the council's rule. For most addresses the Planning Portal test is the working guide, and your building control body is the one to ask.
Basingstoke and Deane shows how careful the wording needs to be. Its list of alteration projects that you "might also need" Building Regulations approval for includes re-covering a flat or pitched roof. Those words apply to its own addresses only, and they say "might", never "will". For a Basingstoke address we check with the council before a re-roof rather than assuming either answer.
For Andover and the Test Valley villages, ask your building control body: local authority building control, or a registered approver. If you are unsure whom to ask, mention it when we visit and we will find the council page for you. The register of approvers started on 6 April 2024, and private building control existed before it.
Our answer on Building Regulations to replace a roof explains the wider process step by step.
Planning permission is a different question
None of the percentages has any bearing on planning permission. Changing the covering on a house normally falls within Class C of the permitted development rules, the class for roof alterations. Under Class C.1(b) the finished work cannot project beyond 0.15 metres from the plane of the original slope.
Flats have no permitted development rights. Listed houses keep Class C but also need listed building consent. A conservation area may carry an Article 4 direction that withdraws some rights: In four Basingstoke town conservation areas, for instance, an Article 4 direction means roof changes now need planning permission, as that council puts it. Which of these points applies depends on the house, so the survey notes whether it is a house or a flat, whether it is listed and whether a conservation area covers it. Elsewhere, ask the local planning authority whether a direction affects your street.
Planning is covered in full under planning permission to replace a roof. Tell us the address and what covers the roof today, and the survey will show which of these points matter on your house.
