Ponding water, blisters or open seams on your flat roof? Flat roof repair cost in Edmonton usually runs $400 to $1,800 for a patch, or about $5 to $12 per square foot when a section needs a new membrane. This guide explains how torch-on SBS, EPDM rubber and TPO systems are repaired differently, which warning signs to watch on garages, additions and commercial buildings, and why every flat roof should be checked each fall.