Garage and outbuilding roof replacement
Garage roofs are usually the oldest covering on the property and the least maintained, which means the deck underneath is the real unknown.
The deck is the variable
Old chipboard or thin ply decks that have been wet for years almost always need replacing. Until the felt comes off, nobody can tell you for certain, so quotes should state the assumption and the rate for extra boards.
Membrane options
EPDM in a single sheet is the usual choice for a domestic garage. Torch-on felt is still viable and cheaper. GRP suits smaller, well-supported decks and gives a harder finish.
Falls and drainage
Ponding water is what kills flat roofs. If the original structure has no fall, adding tapered insulation or firrings during the re-cover is what stops the new roof failing the same way.
Asbestos on older garages
Corrugated cement sheet roofs on older garages may contain asbestos. It must be assessed and removed by a licensed contractor where required — never broken up or jet washed.
Detached versus attached
Attached garages need the abutment to the house handled properly with a flashing or upstand. Detached garages are simpler and usually cheaper for the same area.
FAQs
Only if the deck is dry and sound. Overlaying a saturated deck traps the moisture and the new roof fails early.
Most single garages are a one to two day job including deck repairs.
Usually not for a standard single-storey garage — edge protection and safe ladder access is often sufficient.
Related reading
More on costs & budgeting and the jobs that usually come with it.
- Cost to replace slipped tiles or slatesCosts & budgeting
- Roof cost by house type: terrace, semi, detached and bungalowCosts & budgeting
- Dormer roofs: repair, re-cover and what it costsCosts & budgeting
- New-build roof defects and how to get them fixedProperty types
Looking for something specific? See our roofing services, cost guides, common roof problems or the areas we cover.
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