Our Garage Roof Needs Replacing: Which Option Makes Sense?

Most garage roofs are flat, old and patched. Here is how to decide between a rubber, felt or fibreglass replacement and what to check before the old one comes off.

For a typical flat garage roof, replacement means stripping the old covering, renewing any rotten deck boards and laying a new waterproof system, most often EPDM rubber, torch on felt or GRP fibreglass. EPDM suits most plain garage roofs because it can go down in one sheet with no seams. A pitched garage roof is replaced like a small house roof, with new underlay, battens and tiles or slates.

The right choice depends on the size and shape of the roof, how it drains, what sits against it and whether you want it to match the house.

Signs it is time to replace rather than repair

One split or blister can be patched. Replacement makes more sense when leaks keep appearing in new places, the surface is crazed and brittle across the whole roof, water sits in large ponds after rain, or the deck feels soft or bouncy underfoot when checked. A sagging ceiling inside the garage, or boards that have gone black and crumbly at the edges, points to the deck itself failing.

Old garage roofs often carry several generations of patches. Each layer traps moisture and adds weight, so another repair on top usually buys very little time.

Choosing a flat roof system

EPDM rubber is a single membrane bonded to the deck, with neat trims at the edges. On a garage it usually covers the whole roof in one piece, so there are no joins for water to find. It is quick to lay and needs no naked flame.

Torch on felt is laid in layers and bonded with heat. A modern multi layer felt roof is far better than the thin felt many garages were built with, and it remains a sensible choice where it matches neighbouring roofs.

GRP fibreglass is laid wet and cures into a hard, seamless shell. It handles foot traffic well and forms tidy upstands, which helps on roofs with awkward details. Our flat roofing systems comparison looks at all three side by side.

What happens to the deck and edges

Once the old covering is off, the timber or board deck is checked properly for the first time in years. Sound boards can stay; soft or delaminated ones are replaced so the new membrane has a firm, dry base. This is also the moment to correct the fall, because a garage roof that ponds will shorten the life of any covering.

The edges matter as much as the middle. Drip trims at the front, a kerb or upstand where the roof meets the house wall, and properly dressed flashings stop water getting behind the new system. Guttering and fascias on the low edge are often renewed at the same time.

Pitched and asbestos garage roofs

A pitched garage roof is replaced with the same care as a house roof: new breathable underlay, treated battens and a covering chosen to suit the property. It costs more than a flat roof but lasts longer and often looks better beside the house.

Some older garages have corrugated cement sheet roofs that may contain asbestos. These must not be broken, drilled or cut. Removal and disposal is specialist work with its own rules, so have the material identified before planning any replacement.

A straightforward flat garage roof is usually stripped and re-covered over a short spell of dry weather, with the garage cleared underneath beforehand. Larger, pitched or awkward roofs take longer. Planning permission is not normally needed to re-cover an existing garage roof like for like, though listed buildings and conservation areas can differ, as our planning and building regulations guide explains.

What is the best material for a flat garage roof?

For most plain garage roofs EPDM rubber is a strong choice because it goes on in one seamless sheet. Felt and GRP both suit certain roofs, and we explain the trade offs when we see yours.

Can a new covering go straight over the old one?

It is rarely a good idea. Overlaying hides wet or rotten boards and adds weight. Stripping back lets the deck be checked and repaired first.

Do I need to empty the garage?

Clearing the area under the roof is sensible, particularly if deck boards need replacing, because debris and dust can fall through during the strip.

Can you change a flat garage roof to a pitched one?

Often, subject to the walls, planning rules and the look you want. It is a bigger project than re-covering, so it is worth discussing at the survey.

Is my old garage roof asbestos?

Some corrugated cement sheet roofs from before 2000 contain asbestos. Do not disturb it; have it identified first so removal can be handled correctly.

Garage roof leaking again?

We will look at the deck, the edges and the drainage, then recommend the system that suits your garage rather than the one that is easiest to sell.

Arrange a Garage Roof Visit

Evans Roofing & Maintenance Ltd, Witney, Oxfordshire. Call 07960 482233 for a free written quote.