The short answer
Sometimes. Going by the Planning Portal's general guidance, you can usually skip an application while the job affects under 25 per cent of the building envelope and under 50 per cent of the roof. A heavier covering, or one that behaves differently in a fire, brings approval into play. Its pages are written for houses, so for a shop, unit or barn ask your building control body before work starts.
Replacing a commercial roof can trigger Building Regulations in ways a simple repair does not. The sensible habit is to ask before the first sheet comes off.
The tests the Planning Portal sets out
The Planning Portal is the government's planning and building regulations website. Its re-roofing guidance sets two conditions that must hold together before you can skip a building control application: under 25 per cent of the whole building envelope (every wall, the floor, the roof, windows, doors and rooflights counted together) is touched, and under 50 per cent of the roof itself is touched.
Is it 25 per cent of the roof?
No, and the mix-up catches people out. The first test is a share of the whole envelope, the building's entire outer shell, and the second is a share of the roof alone. Both must hold at once. A wide, low shed with a large roof can pass one test and fail the other.
The Planning Portal's pages are written for dwellings, so for a commercial building treat them as a general starting point and not a ruling. No separate Somerset percentage exists, because Somerset Building Control has published none, so there is no stricter local figure to quote. The straightforward advice for a shop, unit or barn is to put your own case to the building control body and ask what applies.
Weight and fire performance
Two further triggers apply whatever the percentages say. The Planning Portal says approval is required where the replacement material adds 15 per cent or more to the weight of what was there, or where its performance in a fire would differ significantly from the old covering's. Roofers rarely meet the second trigger on like-for-like jobs, but it does arise when a switch of material changes the fire rating.
Why does weight matter on a commercial roof?
Swapping light metal sheeting for a heavier covering, or adding insulation, plant or solar panels on top, loads the purlins and rafters. The Planning Portal advises having a structural engineer or a surveyor look at the weight question first. Do that before you accept a quote, and long before the old roof is stripped, because a bad answer can change the choice of covering altogether.
Fire performance is the other side. A different covering can behave differently in a blaze, and on a building near a boundary, or one holding stored stock, that difference can matter. The product's data sheet and your building control body answer it. We record both points during the survey so they are on the table before the price is set, and a copy of the notes goes to you.
How Somerset Building Control handles it
Somerset Building Control acts for Somerset Council across the whole county area, including the old Taunton patch, and its number is 0300 303 7790. Its charging scheme for houses has a line headed renovation of a thermal element that covers a re-roof or an insulation upgrade, which shows how a notifiable re-roof is billed, though that does not tell you whether your commercial roof is notifiable at all.
Which application route would apply?
Somerset Building Control offers Full Plans, where you usually hear back in 10 working days and normally get a decision within five weeks, and a Building Notice, which it acknowledges after 48 hours at most. Send applications through its own website, or by email, or to its Bridgwater office, and not to the former district council buildings.
A private route also exists. Since 6 April 2024, building control approvers have had to be registered, and a registered building control approver is an alternative to the council for the regulatory check. Private building control existed before then, because only the registration regime is new. Whichever route you pick, ask first and keep the reply.
Ask before work, and what we do
A roof replaced without a needed approval can lead to a regularisation application afterwards. That route is open for work done after 11 November 1985, but it is more awkward than asking at the start.
What should you ask?
Describe the building, the share of roof and envelope affected, the old and new coverings, the weight change and any added insulation. Ask whether an application is needed, which route suits, and whether anything beyond the roof, such as rooflights or an insulation upgrade, comes into it. Keep the answer in writing.
Our survey gathers the facts for that conversation, including photos of the existing build-up and the area of roof involved, and a single written price is set after it. If the answer changes the specification, the price is reworked before any sheet is ordered. The planning side is a separate conversation: see planning permission for a new commercial roof, planning a commercial re-roof and our commercial roofing page. Begin by sending the building's size and its current roof covering.
More on building control
Does overcladding need approval as well?
It can. New sheets over old add weight, and the combined build-up may change how the roof performs in a fire and how it loses heat. Apply the same tests as for a strip and recover: weight, fire performance and the share of envelope and roof affected. Ask your building control body, and describe the overclad system exactly.
Who applies for approval, the owner or the roofer?
The person commissioning the work carries the regulatory side, though a contractor can often apply on their behalf. Agree who does it in writing before work starts. Somerset Building Control expects the dutyholder roles of client, principal designer and principal contractor to be filled on every application it receives.
The full picture: Commercial roofing in Taunton ยท More short answers