Felt almost always wins on the day-one quote, but a felt roof can need replacing two or three times in the life of one EPDM or GRP roof. This tool compares all three on upfront cost and true cost over the years you plan to stay, so you can see which is actually cheaper for your situation rather than just the cheapest to fit.
Compare flat roof options
Plan area of the flat roof. A single garage is roughly 15–20 m².
Lifetime cost is judged over this horizon.
Strip-out, disposal and access added each time the covering is renewed.
Indicative UK figures: felt £40–70/m² lasting ~18 yrs, EPDM £50–95/m² lasting ~30 yrs, GRP £80–130/m² lasting ~32 yrs. Lifetime cost counts how many times each covering must be renewed within your horizon, plus fixed costs each time. Not a quote.