The short answer
Often, yes, though it is a build rather than a re-cover. The walls must carry a new timber frame, the pitch must suit the covering you want, the structure needs building control, and the changed outline is a planning question. Ask Somerset Council's planning team before ordering anything, because a taller garage is no longer a like-for-like job.
A pitched roof sheds water well and looks at home beside a house. It also asks much more of the garage walls than the flat deck it replaces.
Why owners want to swap flat for pitched
Flat garage roofs depend on one waterproof layer, and when it ages the water has nowhere to go. A pitched roof lets gravity carry rain away, and its tiles or slates overlap so that one failed joint does not let the weather in. It can also gain a loft space for storage. Those are fair reasons to want the change.
Is a pitched roof always better than a flat one?
Not always. A well-laid flat roof with a sound deck and proper falls does its job for many years, and it costs less to fit than a framed pitched roof. The change makes sense when the old roof is failing anyway, when the garage is being joined to the house, or when the look of a flat roof next to a pitched house troubles you.
Our page on the attached garage roof looks at the junction where a new garage roof meets the house wall, which is where pitched conversions most often succeed or fail. A visit before any decision lets us look at the walls, the existing joists and the room around the building, and show you photos of each.
What the garage walls have to carry
A flat roof sits on joists spanning the walls, and the load is simple. A pitched roof brings rafters, sloping timbers meeting at a ridge, a wallplate to spread the weight along the top of the walls, and often heavier tiles. The thrust of the rafters can push the walls apart unless ceiling joists or ties hold them together.
Will the walls take a new roof?
That depends on what the walls are. Single-skin brick or block walls without piers can be too slender, and some garage walls are not built to take much load at all. A surveyor or engineer should check the walls, the foundations and the lintel above the door. Even a modest new covering can add 15 per cent or more to the roof's weight, the level at which the Planning Portal wants a structural opinion, and a whole pitched frame adds far more.
Old flat-roof joists should not be assumed fit to serve as the new ceiling ties. They may be undersized, or damp from years of seepage, and wet timber is better replaced than trusted.
Pitch, covering and the flat-roof standard
Every covering has a minimum pitch, and the structure has to be built to reach it. BS 6229:2025 deals with roofs pitched at no more than 10 degrees, so it is the flat-roof standard. Steeper than that, tile and slate rules take over, and the maker's data sheet has the last word.
What pitch do tiles and slates need?
Marley lists a minimum of 22.5 degrees for its smooth Double Roman, 35 degrees for a plain concrete tile and 15 degrees for a Lincoln clay pantile. Natural slate, according to BS 5534 as quoted by Cupa, has a minimum of 20 degrees, with hook fixings not used below 25. A low garage with narrow walls may struggle to reach the pitch a tile needs, which is a real design limit.
Lighter coverings such as profiled metal sheeting suit shallower pitches, and mean a lighter frame. The choice of covering therefore drives the height of the ridge, which then feeds straight into the planning question. We work out the pitch, the ridge height and the covering together before a figure is written down. Compare options in our guide to garage conversion roofs.
Planning, Building Regulations and who to ask
Replacing a flat roof with a pitched one changes the height and outline of the building, so the like-for-like exemption in section 55 of the Town and Country Planning Act does not cover it. Whether permission is needed depends on the building, its position and its use. That is for the council to say, and a short enquiry to Somerset Council's planning team is the sensible first move. Inside Exmoor, the National Park Authority holds the planning role.
Does a new roof structure need Building Regulations?
Expect yes. A new roof frame is structural work, so check with your building control body, which for Taunton addresses is Somerset Building Control on 0300 303 7790. Energy rules apply as well: Table 4.2 of Part L gives a new roof on an existing dwelling a U-value limit of 0.15.
Listed buildings, conservation areas and Article 4 places add their own consents, so tell us if you are in one. Our guide to garage roof planning permission covers the wider picture, and the garage and asbestos roofs page shows what we handle. Your next step is a survey of the garage walls, then one price in writing.
More on changing a garage roof
Can I keep the flat roof and just add a pitched roof over it?
A frame can be built over a flat roof in some cases, but then the old roof is trapped beneath it and the new rafters need walls strong enough to carry both. The old covering is usually stripped first so the structure can be checked. Ask building control before assuming either route.
Will a pitched garage roof add to my property value?
We cannot put a figure on that. It depends on the house, the garage and the local market. What we can say is that a sound, well-finished roof matches the house better and stops a flat-roof leak recurring, and for a number you would need to speak to a local valuer.
The full picture: Garage and asbestos roof replacement in Taunton ยท More short answers