The short answer
Yes, a garage roof can take a rooflight, and it costs far less than re-covering the whole garage. What decides the method is the roof you have: a pitched tiled slope takes a roof window, a flat felt or EPDM roof takes a kerbed rooflight, and an old asbestos cement sheet roof should be tested before anyone cuts into it.
Which kind of rooflight suits which garage roof
Three garage roofs account for most of the questions we get, and each takes a different unit.
Pitched tiled or slated roofs
A pitched garage with tiles or slates takes a roof window, the same family of product used in lofts. It lies flush with the slope, with flashings (the metal or lead strips that seal the joint) lapping over and under the covering. The rafters either side are cut and trimmed with a doubled timber header and sill, so the opening is framed rather than just hacked through.
Flat felt, EPDM or GRP roofs
A flat roof takes a rooflight on an upstand, which is a raised kerb that lifts the glazing above standing water. The kerb can arrive with the unit, or be built on site from timber and then covered with the same membrane as the roof. The membrane is dressed up the upstand and tucked under the rooflight's frame, so the waterproofing is continuous rather than a sealant joint doing all the work.
Sheet roofs
Garages roofed in profiled sheet usually get light a simpler way: a translucent sheet of the same profile swapped in for one or two of the steel sheets. It lets in diffuse light without a separate frame, although it needs the same fixings and end laps as the sheets beside it.
What Part L and the planning rules say about rooflights
Replacement and new windows in an existing home are held to energy limits in Approved Document L (2021 edition). Roof windows must reach 1.4 W/m²K, or alternatively carry an energy rating in Band B. A flat-roof rooflight has a looser limit of 2.2 W/m²K, calculated on the unit's outer surface. When kerb and glazing are supplied as one assembly the 2.2 figure covers both, while a kerb built on site is held to 0.35 W/m²K.
On planning, roof windows fall under Class C of the General Permitted Development Order. Within that class, the unit cannot stand proud of the original slope by more than 0.15 metres, and its top edge cannot rise above the original ridge line. Class C carries no restriction for conservation areas or the Cotswolds National Landscape, unless an Article 4 direction or a planning condition removes it, or the building is listed.
Those rules are written for houses. A detached garage, a garage forming part of a listed property or one in a conservation area can be treated differently, so put the question to Stroud District Council's planning team ahead of ordering the unit. Our page on garage conversions and the roof covers the wider regulation picture if the room is changing use.
Cutting the opening without weakening the roof
On a timber-framed pitched garage, the opening interrupts one or two rafters. The cut ends are carried by a header fixed between the neighbouring rafters, and the load travels round the hole instead of through it. The sill and header also give the flashing kit something square to fix to.
On a flat roof the same thinking applies to joists. A rooflight kerb needs a trimmed opening with a timber frame round it, and the deck around it must be firm enough to carry the upstand. Soft, spongy decking is replaced first, because a new kerb fixed to rotten boards will move.
Falls matter on flat roofs. Under BS 6229 the design fall is 1:40, which leaves at least 1:80 after the deck settles and tolerances are absorbed. A kerb that blocks the natural run of water can create a pond behind it, so on a flat garage roof we check where the water is going to go on the uphill side of the opening and, if needed, form a small tapered section, known as a cricket, to shed it around the corners.
Old garage roofs and asbestos cement sheet
Many garages built around the mid twentieth century were roofed in corrugated asbestos cement. If yours might be one, do not drill, saw or break it to make an opening. HSE guidance allows careful removal of intact, weathered asbestos cement sheeting without a licence, yet work that breaks the material up becomes notifiable, with the enforcing authority told before it starts.
Cutting a rooflight hole into a sheet is breakage by another name, so the sensible order is test first, then decide. If the sample comes back positive, the options are a rooflight in a new roof or a different source of light, such as a side window. Our answer on how to tell whether your garage roof is asbestos explains what to look for, and MyBuilder's 2026 guide puts a basic asbestos survey at £50 and a fuller one at £200 to £245.
If the sheet is something else, such as fibre cement without asbestos, or steel, the cutting method and the edge sealing are different again. We identify the material before we quote.
Cost, heat and the sums to run before you order
MyBuilder's 2026 roof window guide puts installation at £350 to £600 for standard jobs, labour and fitting only, with the unit itself on top. A standard centre-pivot window is quoted at £305 and an electric one at £420 to £590. Scaffold is about £500 where a ladder is not enough to reach the roof safely, though a single-storey garage may need less, so access is worth confirming in any quote.
A flat rooflight over a car makes the garage brighter, but in sun it also makes it warmer, and a large clear panel over a workbench can be uncomfortable in summer. Frosted or tinted glass, or a smaller unit placed above a wall rather than over the middle of the floor, copes better.
Once the survey photographs are in, the written quote covers the unit, the framing, the flashing or kerb, the making good and waste removal, and the finished work carries our 10-year workmanship guarantee in writing. For a neighbouring option on the same subject, see our answer on carport roof replacement, which looks at translucent sheeting in open structures. If the whole garage roof is close to retirement, the garage roof replacement page covers the options.