Do I need Building Regulations approval to re-roof?

The Planning Portal's re-roofing guidance opens with a starting test with two parts. Work is normally outside building control when both of these are true:

• less than 25 per cent of the total building envelope is affected, the envelope being every wall, the floor, the roof and all the glazing and doors added together; and
• under half of the roof, meaning less than 50 per cent, is touched by the work.

The two figures work together, and they are easy to misread. The first is measured against the whole envelope of the building, and the second against the roof alone. Quoting the first as a share of the roof is a frequent slip, and it is not what the guidance says.

It helps to keep a note of what is being done to each part of the roof. Ridge, hips, valleys, verges and the roof edge all count towards the share of the roof affected, even though they look small beside the main slopes, and so do any roof windows and flat sections that are renewed in the same visit. Adding them up on paper before the work starts is far easier than arguing the total afterwards.

Which limit do most houses hit first?

On a typical house the roof is a large share of the envelope, so replacing the whole of it will usually exceed the 50 per cent limit well before the 25 per cent one matters. A complete strip and re-cover of a main roof is therefore normally in application territory. A single slope of a larger roof, or a patch, may stay beneath both limits. Where the answer is close, the better course is to ask your building control body before the work, not after.

The percentages are not the only trigger. The same guidance names other situations that call for approval, and any one is enough:

• the work passes either limit above;
• it includes structural alterations;
• the new covering would perform noticeably differently from the old one if fire reached the roof; or
• the new covering weighs 15 per cent or more above the old.

Because the list is open-ended in that way, a small area can need an application where a large area does not. Fitting a different material over a modest section, or changing a timber, can bring the work inside the rules even though the percentage is low.

What counts as structural alteration?

Anything that changes how the roof carries load. Replacing rafters or purlins, changing the pitch, forming an opening for a roof window or a dormer, removing part of a roof truss for a loft room, or taking out a chimney breast beneath. Replacing a few decayed rafter ends with timber of the same size is repair, but replacing members because they are overstressed, or because they have deflected enough to make the roof pond, is different. Approved Document A calls strengthening of that sort a material alteration. Our page on replacing roof timbers describes the work itself.

Where one house carries coverings from different eras, perhaps an extension roof laid in another material, the survey records what is where. That record becomes the baseline for any later application, and it is useful if you sell, because a buyer's solicitor may ask what was done to the roof and when.

Does fire performance matter on a house?

It matters where the roof is close to a boundary or a neighbouring building, because the covering must resist the spread of fire from outside. Slate, clay and concrete tiles all perform well, so a swap between those rarely raises the point. Some membranes and plastic or metal coverings behave differently, and a change to one of them is a reason to check first.

Weight is the test most often missed. Extra load bears on the rafters and the walls beneath them, and many old roofs were never designed with spare capacity.

The two official wordings differ slightly. The Planning Portal puts the line at 15 per cent or more heavier. Approved Document A, the structural volume, treats extra loading beyond 15% as a significant change. Name whichever one you quote, or treat anything near the line as a question for building control to settle.

Which swaps make a roof heavier?

Moving from lightweight concrete tiles or modern slate to clay pantiles, thick natural slate or real stone slate is the usual case. Stone slate roofs are especially heavy: the Cotswold District Council technical guidance describes them as weighing about 1000 kg per 10 sq m. Going from heavy to light is the reverse. The Planning Portal's re-roofing page applies its weight checks in both directions, and a much lighter covering can alter how well the roof resists wind uplift, so lighter is not automatically safer.

Its advice is to ask a structural engineer or surveyor before the work begins. When we survey, we note the existing covering and its likely weight, and where you want a different material we raise the question before the quote, not after. Our guide to fitting a heavier roof covering covers the arithmetic and the structural options in more detail.

If a re-roof triggers an application, a thermal upgrade may follow. The Planning Portal says exceeding the limits may bring further considerations that could require work to the entire roof, for example ensuring that the thermal insulation is sufficient.

The rule behind that is in Approved Document L, volume 1, which took effect in England on 15 June 2022. Renovating a thermal element, in the document's terms, includes taking a roof down to its rafters and building it back up, and putting a replacement waterproof membrane on a flat roof. Past 50% of the element's surface, or past 25% of the external envelope for a major renovation, the whole element is expected to meet the table's U-value.

What if there is no room for the insulation?

The document accepts a lower standard where the full figure would cost headroom, and expects the insulation and any air gap to be at least as deep as the rafters. Our page on Part L and re-roofing works through the figures, the roof-window limits and the practical routes.

This is one of the reasons we survey the loft as well as the roof. Knowing what insulation is in place, and how the roof is ventilated, tells us before the quote whether an energy upgrade is likely to be part of the job.

Where an application is needed, the application is made either to the council's own inspectors or to a private registered building control approver. Since 6 April 2024, private firms doing this work in England have had to be registered with the Building Safety Regulator under the Building (Registered Building Control Approvers etc.) (England) Regulations 2024.

How does it work with Swindon Borough Council?

Swindon Borough Council runs its own building control service. Its website describes Full Plans as a route for any building work, domestic included, and a Building Notice as an option for domestic work. Applications go in through the council's online forms. Inspections are booked in advance, and the council asks for at least 48 hours' written notice of commencement. The council also offers regularisation for work already done without approval. Its guidance is at swindon.gov.uk.

What about the surrounding areas?

We work out to about 30 road miles, so more than one council can be involved. In the Vale of White Horse, building control is a shared service called Southvale, which also covers South Oxfordshire. Cotswold District Council runs its own building control. West Berkshire is served by Building Control Solutions. For homes under Wiltshire Council, contact Wiltshire Council's building control team. Whichever applies, the rules are the national Building Regulations, and only the route to the inspector differs.

We talk you through consent, and for notifiable jobs the Building Regulations notification is something we make ourselves, so the forms are not left with you. Our roof replacement process shows where that step sits in the sequence of the job.

Building Regulations approval and planning permission are different consents. A re-roof can need one, both or neither.

Putting back the same material generally needs no planning permission, because the appearance of the house stays as it was. There are caveats. A listed house needs listed building consent for any works affecting its special interest, and the roofing material is often part of that character. An Article 4 direction can remove permitted development rights in an area, and conservation areas bring their own scrutiny. Changing the covering to a visibly different material is more likely to raise the question than replacing slate with slate. Our page on planning permission for a re-roof goes through those cases, and if your house is in a protected area, the planning team at Swindon Borough Council can confirm where you stand.

Does the old felt or underlay raise any rules?

Removing the old underlay is part of the strip and is not a separate approval. What matters is what replaces it, because a breathable membrane and the right ventilation are part of keeping the roof structure dry. We explain the sequence in our guide to removing old roofing felt.

If you are unsure whether your job needs an application, the mistake most worth avoiding is starting without asking. Our written ten-year workmanship guarantee only means something on a roof that was built lawfully, so we check consents before any scaffold goes up. The wider job is on the main roof replacement page.