Garage roof rules

Do you need planning permission to replace a garage roof?

Planning permission and building regulations are separate tests. A like-for-like covering does not normally need the first, and the second turns on how much roof is renewed.

The short answer

Not normally, where the garage is part of a house and you are only changing the covering. Class C of the permitted development rules is the one for roofs, and re-roofing falls within it. The limits bite on height, projection, chimneys and solar, and some homes sit outside it. Building Regulations are a separate test, and a roof over a separate outbuilding is for your council to rule on.

4 min read · Part of Garage roofs

Planning and what Class C covers

Permitted development means work you can do without applying for planning permission, because national rules already grant it. For a house roof, the rule is Class C: "any other alteration to the roof of a dwellinghouse". A change of covering, such as new tiles or a new membrane, sits within it, and the rule has no condition about matching the old materials.

It stops short of work that would rise above the highest point of the original roof, stand more than 0.15 metres proud of the original slope, or include a chimney, flue or solar equipment. That is why turning a flat garage roof into a pitched one is a separate question: see our page on flat garage roof to pitched.

A garage that stands apart from the house is an outbuilding, and the rules for outbuildings differ from Class C. Ask the council that covers your address before you assume anything, and keep its reply in writing. The same goes for an integral garage under the main roof: its covering is part of the house roof, and the house rules apply to it.

Homes where the answer changes

Four situations move the answer away from the plain rule.

Listed homes keep their permitted development for roof work, but listed building consent is needed for anything that affects the building's character. The consent comes from section 7 of the Planning (Listed Buildings and Conservation Areas) Act 1990, so check before you start.
Flats and maisonettes have no permitted development, so planning permission is needed for changes to the outside.
Article 4 directions can remove rights from an area. What each council's direction covers is for that council to say.
Conservation areas and National Landscapes leave ordinary re-roofing as permitted development, but they remove dormers from the permitted list.

Check which applies before you order materials, since a refusal is easier to deal with at the start than halfway through the job. Our planning permission guide sets out the conditions on one page, with the full wording of the rule, and it is the page to read before you start. It also covers how to check whether your road sits under an Article 4 direction, which is a question for the council, not for a builder.

Building regulations: a different test

Under the Planning Portal's guide, re-roofing does not normally need a building regulations application if it affects less than 25 per cent of the building envelope and less than 50 per cent of the roof. Putting on a covering that is 15 per cent or more heavier does need approval, as does a new covering that would not match the old one for fire performance.

The Portal counts walls, floor, roof, windows, doors, roof windows and roof-lights in the building envelope, so a garage roof is a small part of that whole, yet it can be all of the roof you are renewing, and the roof limb is the one to watch. A small building can make a large share of roof out of one slope. Building control comes from the council's own team or a private registered approver, and a quick call before you order materials costs nothing.

On a Dover District Council address, the council counts replacing roof coverings, pitched or flat, as work needing approval even when it is like for like. Everywhere else the Portal's test applies, and none of the councils we work in gives a percentage of its own. Where the weight changes, the Portal's advice is a structural engineer's or surveyor's check first.

What we check before you spend anything

Part L of the Building Regulations, on fuel and power, comes in when over half the area of a roof is renovated. AD L 2021 then expects the whole element to reach the improved 0.16 W/m²K in Table 4.3 (threshold 0.35) where that is feasible, and AD L counts re-covering a flat roof with a new waterproof membrane as renovation. Whether it reaches a garage that stays a garage is for building control to confirm.

Before any work starts we:

Work out whether the garage is part of the house or a separate outbuilding.
Check for listing, a conservation area and any Article 4 direction.
Work out the share of the roof that the job renews.
Check whether the new covering is heavier than the old.

Each answer goes into the survey notes. That gives one written total price after a survey, with the building control route named and the date it was checked. The garage roofs hub has more, and the garage roof lifespan page helps you judge when to start.