The short answer
A concrete sectional garage can be re-roofed in several ways: new box-profile or corrugated sheet on the existing purlins, a flat covering such as felt or EPDM on a new deck, or a fresh pitched structure. Before anything else, we identify what covers the garage now, since older cement sheets may contain asbestos. Which option suits depends on the frame, the fall and your budget.
What a sectional concrete garage roof is made of
A precast concrete garage arrives as wall panels, posts and a roof kit, then goes together on a prepared base. The roof is rarely concrete. Most are corrugated sheets laid over timber or concrete purlins (the cross-members the sheets rest on), usually at a shallow pitch, while some have a flat deck with a felt covering.
That matters for two reasons. The panels are strong, so a replacement can be fixed to the existing frame, but the roof beams were designed for a light covering and should not be asked to carry a heavy one. And the sheets on older garages are often cement-based, which means asbestos has to be ruled out before anyone drills, cuts or lifts them.
Our answer on which covering to choose for a garage sets out the general choices. The rest of this page deals with what is particular to a concrete garage.
Check for asbestos before you choose anything
Asbestos cement was widely used for garage sheeting for many years. You cannot tell by looking, so a sample is tested or the sheet is treated as asbestos until it is shown not to be. Under HSE guidance, lifting asbestos cement sheets carefully and in one piece counts as non-licensed work. Once they are substantially broken up, the same job is notifiable non-licensed work and has to be reported to the enforcing authority before it begins.
In practice this decides the programme. If the sheets are intact, they come off whole, are wrapped and leave site as hazardous waste. Our page on how asbestos roof sheeting is disposed of covers wrapping and carriers.
MyBuilder's 2026 asbestos removal guide puts a single garage roof at £350 to £1,295 and a double at £650 to £1,800 for removal. That sits on top of the cost of the new roof, so keep it in mind when you compare quotes.
Replacement options for a precast garage
New sheet on the existing purlins
The simplest swap is a modern profile sheet fixed to the same rails. Box-profile steel with an anti-condensation backing suits many garages: it weighs little and goes up fast. The purlins have to be sound and at the right spacing for the new sheet, and any that have rusted or split are replaced first.
A flat roof on a new deck
If the garage is nearly flat or you want a cleaner finish, a timber deck can be built over the panels and covered in felt, EPDM or GRP. MyBuilder's 2026 flat roof guide gives bitumen felt £70 to £100 per m², EPDM £90 to £130 and GRP £95 to £150. A flat deck needs a fall to drain, and the standard guidance is a design fall of 1:40 so that finished falls reach at least 1:80.
A pitched replacement
A new pitched frame and tiles or sheets can transform a tired garage and add storage space in the roof. It is a bigger job and a heavier covering, so we check the walls and how the panels are tied together, and the Building Regulations may apply. We cover that in turning a flat garage roof pitched.
Fixings, joints and the faults we find
Precast garages tend to fail at the joints. The panels sit tight against one another, and over the years the sealant between them dries out, the bolts rust and the top edge of the wall takes water. We look at the head of each panel, the fixing brackets and the ring beam, if there is one, before pricing the roof.
Condensation is another common complaint under sheet roofs on concrete garages, because the concrete stays cold and the air in the garage is damp. Our page on why a metal garage roof drips inside explains the cause and the usual fixes, which often start with a backing layer and some ventilation at the eaves.
We also check the overhang and the guttering. A roof that sheds water onto the top of the wall panels soaks the joint below it, so the details at the eaves are renewed with the covering, not left as they are. Fascia boards, brackets and any rusted fixings come off at the same visit, which saves a second round of access later.
Reaching a decision and getting a written price
For a typical garage the choice comes down to three questions: what is the roof made of now, can the frame take the new covering, and how long do you want it to last? In MyBuilder's 2026 figures, a single flat garage roof is typically £700 to £1,000, a double £900 to £1,400 and a pitched roof £2,500 to £4,500.
Those are national figures. Your quote is built from your own garage, so we measure, photograph the roof and the panel joints, and the quote covers removal and disposal, repairs to the frame, the covering, the edge details and clearing up. Should the job fall under the Building Regulations, we walk you through the consent and look after the notification.
To begin, send us photographs taken outside and inside the garage, or ring 01453 933613, or use the enquiry form. Our workmanship is guaranteed for 10 years in writing. More on the wider choices is on the main page for garage roof replacement, including felt, EPDM and sheet.