Box profile steel sheeting
Pre-coated steel box profile is the most popular choice for a pitched garage roof. It is light enough for old rafters, quick to fit, long lasting and available in several colours. The trade-off is noise and condensation on bare sheets, which a foam backing or insulated sheet fixes.
Cement-free fibre sheets
Modern fibre cement sheets look much like the original corrugated roof, which suits garages in a row. They are quieter than bare steel and fire resistant, but they are heavier, can be brittle underfoot, and need more fixings. They are a good choice when a uniform look matters.
Bitumen corrugated sheets
Low cost and quiet, with a short life compared with steel. They can sag in hot weather and fade. They suit a budget job where the garage is not heavily used.
EPDM rubber and flat roofs
For a flat or low-pitched garage, a one-piece EPDM rubber membrane or a GRP roof gives a seamless waterproof finish. It needs a good deck and careful edge detailing, and it costs more than sheeting, but it can last decades and gives a clean look.
Flat roofs are also easier to fit solar panels to using ballast or low-angle frames.
Quick answers
Which is cheapest?
Bitumen corrugated sheeting is usually cheapest to buy, steel box profile is the best balance of cost and life, and EPDM or GRP costs most.
Which is best for solar panels?
Steel box profile with proper rails, or a flat roof system with a ballasted frame, are both common. Tell your installer before choosing.
Will a new roof need insulation?
Only if the garage is used as a workshop or living space. For ordinary storage a backed sheet that stops condensation is usually enough.