Why garages and workshops suit a tubular skylight
Most garages are dark boxes with one up-and-over door and perhaps a small side window, and a sun tunnel adds even daylight from the roof without adding a window to secure or a pane to shade.
A sun tunnel, also called a tubular skylight, collects light through a small dome on the roof, carries it down a reflective tube and spreads it through a diffuser in the ceiling. In a garage that means you can open the side door on a February afternoon and see the bench, the shelving and the car without reaching for the switch. Because the opening in the roof is small, there is no large pane for anyone to climb through and no view into the garage from outside, which matters for a building that often holds bikes, tools and garden machinery.
Cambridge helps here. The land is flat and roofs are rarely shaded by hills, so a garage roof tends to see a wide band of sky. A sun tunnel works from the whole sky, not only direct sun, so it still gives useful light on an overcast day. Our guide to how sun tunnels work explains the dome, tube and diffuser in more detail, and the sun tunnel installation page covers the service as a whole.
Detached, attached and integral garages are different jobs
Where the garage sits in relation to the house decides how simple the installation is, so it is the first thing we ask about.
- Detached garage. A separate building at the end of the garden or down a shared drive, common behind 1930s semis in Cherry Hinton or Chesterton. The tube runs straight from roof to ceiling, often with no loft at all, and there is no link to the house to protect.
- Attached single-storey garage. Built against the side of the house with its own flat or lean-to roof. The tube again runs through the garage roof only, but the shared wall with the house still matters for fire separation.
- Integral garage. Built within the footprint of the house, usual on many estate homes and on newer homes around Cambourne, Great Kneighton and Northstowe. There is often a bedroom or a room in the roof above, so a tube cannot simply go straight up.
For an integral garage with a room above, the tube may have to take a longer route with bends, or the idea may not be practical at all. Every bend and every extra metre of tube costs light, which our guide to sun tunnel length and bends explains.
Fire separation in integral and attached garages
An integral garage is separated from the house by walls and a ceiling built to resist fire, and anything that passes through that separation has to keep it intact.
Approved Document B, the fire safety part of the Building Regulations guidance, expects a garage attached to or within a house to be separated from it by fire-resisting construction. In practice that usually means the wall between garage and house, and the ceiling of an integral garage where there is a room or a shared loft above. A sun tunnel that runs through the garage's own roof into the garage alone does not cross that line. A tube that passes through the garage ceiling into a loft space shared with the house, or through a floor into a room above, does cross it, and the detail around the tube then matters.
Some manufacturers offer fire-rated collars or ceiling details for their tubes, but what is available varies by product and we do not assume any particular one will be accepted. Building Control is the body that decides whether a proposed detail maintains the fire separation, and where the work is notifiable we handle the notification and agree the detail before we cut. If a route through the separation cannot be made acceptable, we will say so at the survey and look at a route through the garage's own roof instead.
Our answer on whether sun tunnels need Building Regulations covers notifiable work more widely, and the planning permission answer covers permitted development, which usually applies to a garage roof in much the same way as to the house, with exceptions for listed buildings and some conservation settings.
Garage roofs and what they mean for the dome
Garage roofs vary far more than house roofs, and the roof covering decides which flashing or upstand kit we use.
| Garage roof | What it means |
|---|---|
| Felt, EPDM or GRP flat roof | Flat roof kit on an upstand, short tube |
| Concrete or clay tiles | Pitched roof flashing, as on a house |
| Corrugated sheet | Sheet type checked first, fixing detail varies |
| Old or tired covering | Best combined with a new roof |
Many prefabricated and older garages have corrugated sheet roofs. Some older fibre cement sheets contain asbestos, so a sheet roof of uncertain age should be tested by a qualified surveyor before anyone cuts it. If the garage roof is near the end of its life, fitting the sun tunnel at the same time as a new covering gives the cleanest result. The guides to sun tunnels for flat roofs and sun tunnels for pitched roofs show how each kit sits on the roof.
Getting the light right for a workshop
A sun tunnel gives even, general daylight, so in a workshop it is best treated as the background light, with task lighting at the bench.
The position of the diffuser matters more in a garage than in most rooms. Over the middle of a car bay it lights the roof of the car and little else. Over the aisle in front of a workbench, or between the bench and the shelving, it puts light on the surfaces you actually use. A longer garage or a double garage may justify two tubes rather than one larger one, so the light reaches both ends. Our answer on how big a room a sun tunnel can light explains how tube size relates to floor area, though exact output varies by manufacturer and we confirm it at the survey.
Garages are also used after dark, for the school run in winter or an evening at the bench. A tube gives no light at night on its own, but an integrated LED kit lets the same diffuser provide electric light in the evening. The guide to sun tunnels with LED lights explains how those kits work.
Heated garages, gyms and condensation
In a cold, unheated garage the tube behaves much like the air around it, but once the garage is heated and used as a gym, office or workshop, the tube needs insulating where it passes through any cold space.
Warm, moist air meeting a cold tube surface is what causes condensation. If you heat the garage in winter, or run a tumble dryer in it, we insulate the tube through the roof void and seal it properly at the ceiling. The answer on whether sun tunnels cause condensation sets out the approach. If the garage is being converted into a habitable room, that conversion is building work in its own right, and the light for it is best planned as part of the conversion, where a rooflight may suit better than a tube.
Questions people also ask
Can I put a tubular skylight in a prefabricated concrete garage?
Often, yes, as long as the roof sheets or panels can take a sound fixing and the sheet type has been checked. We look at the roof at the survey and, if the covering is old, may suggest renewing it first.
Is a sun tunnel secure enough for a garage?
The roof opening is small and fully closed by the dome, so it does not create an opening a person could climb through in the way a large rooflight might. It gives light without giving a view of what is stored inside.
Would a rooflight be better than a sun tunnel in a garage?
If the garage roof sits directly over the space and you want more light or fresh air, a flat rooflight or roof window can give more. Our sun tunnel versus skylight guide compares the two, and a light survey settles it for your garage.
Can the tube go through the room above an integral garage?
Sometimes, but it crosses the fire separation between garage and house and takes up space in the room above. Building Control decides whether the detail is acceptable, so we treat it as a case-by-case question rather than a standard fit.
