The short answer
Yes, clear sheets can be used on a garage roof, usually a few panels among solid ones to let in daylight. Polycarbonate lasts longer and is tougher than PVC. A whole clear roof makes a garage hot and glary in summer and costly to heat in winter, and the sheets can be fragile underfoot, so no one should walk on them. Profile, pitch, fixings and the supporting frame all have to match.
Why people choose clear sheets
A garage with no windows is dark, and a workshop or hobby space without light is miserable. Fitting a few clear panels into a corrugated roof is a cheap way to bring daylight in without cutting into walls. The sheets are light, easy to cut and available in profiles that match common corrugated and box-profile sheets, so they can sit alongside a metal or fibre-cement covering.
They also suit a lean-to carport, a covered walkway and a utility store, where light is valuable and appearance less so. For a whole garage roof the case is weaker, because the same openness that lets light in lets heat, glare and prying eyes in as well.
The materials
Polycarbonate is a tough clear plastic with good impact resistance and UV protection when sold with a co-extruded coating. Twin-wall and multi-wall versions trap air inside the sheet, which insulates and cuts condensation. Corrugated polycarbonate is simpler and cheaper. PVC sheets are cheaper still, but they yellow, become brittle and crack with age and sunlight. They tend to need replacing sooner.
Always choose the material for the use: a UV-protected polycarbonate on the sunny side, and be sceptical of the cheapest unbranded PVC. Our page on which roofing sheet is best compares the full range of sheet coverings.
Heat, glare and condensation
A clear roof acts like a greenhouse. In summer the garage heats up, and tools, paint and cars suffer. In winter it loses heat faster than an insulated solid roof. Tinted or opal sheets reduce glare and heat but also cut light. Condensation forms on the underside of cold clear sheets when warm moist air meets them, and drips onto whatever is below. Our guide to condensation under a metal roof deals with the same issue on solid sheets.
Keeping the clear area small helps. A few panels, set near the ridge or at the back, give light without turning the garage into a glasshouse.
Safety: clear sheets are fragile
The most important point is that a clear sheet is not designed to take a person's weight. Old, brittle sheets covered in moss are hard to spot, and falls through fragile roofs cause serious injuries. Anyone who goes up must stay off the clear panels and use crawling boards that span the supports. Mark the panels where you can. This matters for repair and cleaning as well as installation.
Fixings must go through the crests with the correct washers, and sheets must be supported at the spacing the maker states. Under-supported clear sheets sag and crack. A pitched garage roof is also needed, because the laps rely on a slope to shed water, so a clear sheet is the wrong choice on a flat garage roof. See our guide to garage roof materials for the options that suit low pitches.
Matching the profile and the frame
A clear sheet has to fit the sheets around it. Corrugated, box profile and trapezoidal sections are not interchangeable, and an odd match leaves gaps at the laps where rain blows in. Buy sheets cut to the same pitch of wave and the same lap width as the rest, and fit them with matching ridge, flashing and end-closure pieces. Plastic expands and contracts far more than metal, so the fixing holes are drilled oversize to let the sheet move, and fixings are not over-tightened. A sheet pinned hard against its frame in summer will split in the first cold spell.
Alternatives to clear sheets
If daylight is the aim, a rooflight set into a proper kerb is more weatherproof than a clear sheet and can be insulated. Windows in the gable wall, or a glazed door, bring in light without a roof opening. Light tubes carry daylight down from the roof through a reflective pipe and take less space. For a garage that must stay cool, a solid insulated roof with one or two openings performs better than a clear one.
Security and privacy
A clear roof lets people look in from upstairs windows next door, and at night it shows lit rooms and stored goods. Opal or frosted sheets keep the light and lose the view. Clear plastic is also easier to break through than metal, which is something to weigh if the garage holds tools or a bike. Keep valuables out of sight lines and fit a good lock on the door.
Our approach
If you are replacing a garage roof and want some daylight, we discuss placement in the free survey. We photograph your roof and frame, check that the structure suits the sheets, and say if clear panels are a good idea in your case. The fixed written quote names the sheet and the fixings, and ten years of written workmanship cover stand behind the roof. The broader range of work is under garage roof replacement.
Every roof is different. A free survey with photos settles it for yours.
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