The short answer
It varies widely. A cheap felt roof laid thinly may fail within a few years, while a good rubber or fibreglass roof on a sound deck can last much longer. Metal sheets and concrete sections can run for decades, though rust, cracks and failed fixings eventually end them. Fitting, drainage, shelter from weather and regular upkeep often matter as much as the material itself.
Why there is no single figure
Garages are built in many ways. A modern brick garage with a pitched tiled roof is a different animal from a 1960s sectional concrete garage with a flat roof, or a timber lean-to under corrugated sheet. Each material ages by a different route, and the same material ages at different rates depending on shade, trees, orientation and neglect. A lifespan quoted without that context is a guess.
Instead of a number, it is more useful to know how each type wears out, what hastens it and how to spot the signs. That lets you judge your own roof.
Felt, rubber and fibreglass
Flat garage roofs are usually covered in felt, EPDM or GRP. Felt lives or dies on quality and number of layers. A single cheap layer cracks and blisters early, while a multi-layer polyester-reinforced system lasts far longer. EPDM rubber is flexible and has few joints, so it often outlasts felt, provided the edges and upstands are sound. GRP is hard and durable when the deck is stiff, but it cracks if the structure moves. Our page on how long a flat roof lasts compares the three in more detail, and the felt end of the scale is dealt with in how long shed felt lasts.
Metal and sheet roofs
Coated steel and aluminium sheets can last well, but the coating wears, cut edges and fixings rust, and sheets that were thin to start with dent and loosen. Condensation underneath speeds rust from inside. Bitumen sheets are lighter and quieter but age faster in sun and can sag. Fibre-cement sheets last long but become brittle and mossy. Our guide to garage roof materials compares these in detail.
Concrete and asbestos cement
Sectional concrete garages have panels that can last a very long time, but their joints and the flat or shallow roof sections are vulnerable to water, and steel reinforcement inside can rust and burst the concrete. Asbestos cement sheets, which were widely used before the 1990s, weather but last a long time. They become brittle, crack, and shed surface debris, and many are now well beyond what was expected of them. If you have one, do not treat it casually. Our page on whether your garage roof is asbestos explains how to find out.
What shortens a garage roof's life
Water that cannot escape is the main enemy: blocked gutters, no fall, ponding. Overhanging trees drop leaves and sap and keep the surface damp. Poor fixing in the first place, thin material, bad laps and no edge details lead to early failure. Moisture inside the garage causes rust and rot from underneath, which our guide to condensation under a metal roof explains. Foot traffic and heavy loads on a roof not built for them cause damage as well.
Repair, patch or replace
Deciding when to stop repairing is the hard part. A repair makes sense when the fault is confined to one spot and everything around it is in good order: a split seam, a few cracked sheets, a lifted flashing. Replacement makes sense when failures are spread across the roof, when new ones keep appearing, when the frame or deck is soft, or when the cost of repeated repairs approaches the cost of a new covering. A good test is to ask whether the next repair will still be holding in a year. If you doubt it, the roof is probably spent. Our guide to repairing or replacing a garage roof goes into the decision.
Garages in sheltered and exposed spots
Location changes the answer. A garage in the lee of a house, away from trees, ages slowly. One on an open plot takes wind that lifts edges and driven rain that finds laps. A roof beneath a mature tree gets leaf litter, shade and constant damp, which feed moss and block gutters. A south-facing slope takes the most sun, which bakes felt and fades plastic. Mention these when you get a quote, because the right covering for a shaded, wet roof is not always the right one for a hot, open one.
Signs a roof is nearing the end
Look for sheets that are cracked, sagging or lifted, felt that is split or bubbled, rust at fixings and edges, daylight through the roof, damp patches on the ceiling or walls, moss mats that stay wet, and joists that look dark or soft. Several of these together are a sign that patching will buy only a little time. A single failure may be a repair job.
The free survey for a garage roof includes pictures of your own roof, the frame and the underside, so you can see how much life is left. We say if a repair is enough, and the fixed written quote covers whichever route is right. New roofs carry ten years of written workmanship cover from us. Take a look at garage roof replacement for the main options.
Every roof is different. A free survey with photos settles it for yours.
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