Plenty of owners assume a new roof is a planning matter. It is not. Planning permission concerns how a building looks and what it is used for. Building Regulations ask something else entirely: is the work safe, structurally sound and sensible on energy? A re-roof can fall under them even when the house looks identical afterwards.
Whether yours does comes down to a handful of checks. Two measure size: how much of the whole building envelope you are touching, and how much of the roof itself. The rest ask what you are changing, namely the structure, the weight of the covering and its behaviour in a fire. Trip any one and the work needs approval before it starts, and a roof that must be upgraded for heat loss adds a further layer.
What follows quotes each test as the Planning Portal words it, then explains how it plays out on a Worthing street, who inspects, and which paperwork we deal with. Where a point is a judgement for the building control body rather than a fixed rule, the text says that plainly.
The two size tests, word for word
The Planning Portal sets two conditions. Meet both, and a repair or re-cover normally goes ahead without any building control application. The first: "Less than 25 per cent of the total 'building envelope' (walls, floor, roof, windows, door, roof windows and roof-lights) is affected". The second: "Less than 50 per cent of the roof is affected." Both limits have to be met together. Pass one and fail the other, and an application is needed.
What the envelope takes in
The envelope is the entire shell of the building: its walls and floor, the roof, the windows and doors, plus any roof windows or rooflights. The 25 per cent limit is a share of all those surfaces added together. The 50 per cent limit is a share of the roof alone. Mixing the two up produces the wrong answer, so keep them apart when you read any summary online.
Where a typical job lands
Stripping and re-covering a whole roof affects every part of it. That is far beyond the 50 per cent line, so the job goes down the approval route. Re-fixing a few slipped tiles or dressing one flashing falls inside both limits with room to spare. Between those poles sit jobs such as re-covering just one side of a roof, where the percentages turn on the shape of the house and the size of the slope. In those borderline cases the building control body, rather than any roofer, has the final word, and we raise the question during the survey instead of guessing at an answer.
Our roof replacement page sets out the wider job these rules sit inside.
Triggers that apply whatever the size
The same Planning Portal page names further reasons for approval. You need it if you "exceed the limits stated above", if you "carry out structural alterations", if "The performance of any new covering will be significantly different to that of the existing covering in the event of a fire", or if the new covering makes the roof 15 per cent or more heavier than before.
Structural alterations
Cutting into rafters, adding or moving a purlin (the heavy horizontal beam that carries the rafters), raising a ridge or forming a fresh opening all count as structural. A like-for-like re-cover leaves the frame alone, yet a survey occasionally uncovers rotten timber that must be replaced or strengthened, and that can lift an ordinary job into this category. Whenever we find it, you see the timber and the cause in the survey pictures before anything is decided.
Fire performance
Approved Document B, the fire safety guidance, now carries 2025 amendments that removed the former national classes for roofs. Coverings close to compartment walls are specified by the European class BROOF(t4). A covering that would perform differently in a fire from the one it replaces therefore invites a second look, and we read the product's classification before ordering, never after fixing.
Heavier coverings
Moving to a heavier covering is a test in its own right, because the extra load lands on timbers sized for something lighter. The two official wordings part company by a hair at exactly 15 per cent, a gap we unpick in switching to a heavier roof covering. Whichever wording you read, the sensible response is identical: a structural check, then an application.
When insulation has to come up to standard
Clearing the size tests does not end the matter if you go over them. The Planning Portal cautions that exceeding the limits may bring further considerations, such as ensuring the thermal insulation is sufficient. Its re-roofing page adds that the roof can be treated as a thermal element, and brought up to current performance.
The detail sits in Approved Document L, Volume 1 for dwellings, in the 2021 edition incorporating 2023 amendments, which took effect on 15 June 2022. Under that document, stripping a pitched roof to its frame and rebuilding it counts towards renovating that thermal element, and so does a new waterproof membrane on a flat roof. The whole element has to be upgraded once renovation reaches over 50% of that element's surface, or when the job is a major renovation, which is defined as renovating more than 25% of the external building envelope's surface area.
For a new or replacement roof element in an existing dwelling, Table 4.2 sets a limiting U-value of 0.15 W/(m²·K). The lower the U-value, the less heat escapes. That number decides how much insulation goes in and where it sits.
What this means on site
Extra insulation is no bolt-on extra. Placing it above, between or beneath the rafters alters the eaves detail, the airflow through the loft and sometimes the height of the roof edge. On a flat roof it changes the build-up and the upstands. These choices belong at survey stage so that the written quote reflects them. Our guide to insulating when you re-roof compares the options, and whether the insulation part earns the zero rate of VAT turns on how the work is split into supplies, and we spell that out when we price the job.
Who checks the work: the council or a registered approver
Once an application is needed, there are two routes. One is the council's building control team. The other is a private firm acting as a registered building control approver, the title that has applied since the Building (Registered Building Control Approvers etc.) (England) Regulations 2024 took effect on 6 April 2024. GOV.UK states that private businesses wanting to do this work in England must register with the Building Safety Regulator. Older articles sometimes use a different job title for these firms, and that wording belongs to the previous regime.
Adur and Worthing building control
The two councils run one team from Worthing Town Hall on Chapel Road, open Monday to Friday, 9am to 5pm. Its email address is building.control@adur-worthing.gov.uk, and the council's contact page lists the telephone line. Although Adur and Worthing remain separate planning authorities, this one team serves both.
What the councils say about the service
Their service update says inspectors holding the new registration are in short supply across the country. Building control must be told by the owner at set points in the build, and inspections are booked by phone. Since 6 April 2024 the team concentrates on statutory work, and design advice is off the table for it. Fees carry VAT apart from regularisation fees, and domestic charges have been published from 1 April 2026.
That shapes how a job is planned. Nobody at the council can design your roof for you, so the specification comes from the survey and the maker's data sheets. We build the inspection stages into the order of work, because an inspector has to see certain details before they disappear under the next layer.
What happens on a job that needs approval
When a job is notifiable, we explain what consent applies and file the Building Regulations notification ourselves. Sequence counts for more than forms here, so this is how a notifiable job unfolds.
Before the quote
The survey comes first. We go into the loft and out onto the slopes, note the roof's construction and the state of its timbers, and measure the area. From that we can tell you plainly whether the job sits inside the two size tests, clearly beyond them or on the border. The quote is written, gives one total price, and comes with a set of pictures of the faults we found. Where the building control route affects it, the quote says so. Cost is driven by access, the covering chosen, the roof's area and whatever the survey turns up, and an application adds fees to the picture. Whether a quote includes VAT and scaffolding is worth checking, since those two items swing totals most.
During the work
You are told which stages an inspector will visit, such as the structure before boarding goes over it or the insulation before it is covered, and those stages go into the programme. Waiting for an inspector can stretch a job, which is one reason the length of a re-roof differs from house to house, and why a start date firms up only once the inspection stages are booked. On bigger roofs the gaps between those visits are worth planning around, so the loft is never left open to the weather while an inspector is awaited.
Afterwards
Skips and sweepings go when we do, so the clearing up is not left to you. Keep every letter and certificate that building control sends, filed with your other house papers. They record that the work was inspected, and a later buyer's solicitor may well ask for them. Keep the survey photographs in the same folder, because they show the roof as it was before the work began.
What building control does not decide
Building control and planning are separate systems with their own thresholds, and confusing them is a frequent muddle on this subject. The 50 per cent figure is a Building Regulations threshold. It bears no relation to planning permission, and re-covering over half a roof does not on its own create a planning requirement.
Planning in brief
Under the Town and Country Planning Act 1990, work that doesn't materially change a building's exterior look falls outside the definition of development. A plain swap for an identical covering seldom needs consent as a result. Two caveats apply: a listed building brings listed building consent, and an Article 4 direction can withdraw permitted development rights in particular streets. Both are covered in re-roofing a listed or conservation-area home. If you are unsure, put the question to the Adur and Worthing planning team before work starts.
Approval is not a grade for the job
A building control sign-off confirms that the work met the regulations on the points inspected. It does not stand in for a good survey or a sound repair, and it does not mean the job was the right scale. We still recommend the smallest work that cures the fault properly, and we say when that means a repair rather than a replacement. For the official wording of the thresholds quoted above, the Planning Portal sets them out in its re-roofing guidance. Fire performance, structure and heat loss are each a separate question on that page, so read all three before you commit to a specification, and ask us at the survey if one of them is unclear.
