Not sure whether to repair or replace your roof? Many Edmonton roofers use the 30 percent rule: if a repair costs more than about 30 percent of a full replacement, or your asphalt roof is 18 to 20 years old, replacing it is usually the smarter investment. This roof repair cost guide includes a simple side-by-side checklist covering roof age, shingle condition, decking and repeat leaks to help you decide with confidence.