Repair if the roof is less than two-thirds through its lifespan, the problem is localized (one flashing, one drain, a small area) and the repair costs well under 25% of a replacement. Replace if leaks keep coming back in several places, the membrane is cracked over large areas, or the deck or insulation is wet or rotten.
Decision table
| Situation | Lean repair | Lean replace |
|---|---|---|
| Membrane age | Under 2/3 of its lifespan | Near or past its lifespan |
| Extent | One flashing, drain or area | Several areas, repeat leaks |
| Deck and insulation | Dry | Wet, rotten, sagging |
| Repair cost | Small share of a replacement | Over 25% of a replacement |
Check typical ages in how long a flat roof lasts and amounts in our cost guide. Most leaks are fixed with a targeted repair if you act fast.
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The 25% rule is a general benchmark, not an absolute rule. Only an inspection shows your roof’s real condition.