Repair, Maintenance, and Reroofing
This domain tests condition assessment and the decision that follows: repair locally, recover over the existing roof, or tear off to the deck. It covers moisture surveys, core cuts, code limits on layers, and the practical details of a reroof.
Assessment
Start with a walkover for blisters, splits, ponding, open seams, failed flashings and deteriorated curbs, then confirm with a moisture survey using infrared, capacitance or nuclear meters. Verify findings with core cuts; a wet core means wet insulation, which must be removed, because a new membrane over wet insulation blisters and fails. Ponding is generally defined as water still standing 48 hours after rain.
Repair methods
Local repairs include patching with compatible membrane, re-welding or re-splicing seams, rebuilding flashings, and replacing wet insulation in cut-out squares. Compatibility matters: patch TPO with TPO, EPDM with EPDM splice material, and never apply a solvent adhesive to TPO.
Recover versus tear-off
Recovering over an existing roof is permitted only where the deck is sound, the existing layers are firmly attached, the total number of layers stays within the code limit (commonly two shingle layers on steep slope), and flashings can be rebuilt to full height. Tear-off is required where insulation is wet, where the deck cannot carry another layer, or where the layer count is already at the limit.
Worked example
A 20 m by 15 m roof is surveyed on a 3 m grid: 7 columns by 5 rows gives 35 probe points. Six points read above the moisture threshold. Each grid cell is 9 m², so the suspect area is 6 × 9 = 54 m². Confirm with three core cuts, then plan to remove and replace roughly 54 m² of insulation plus a margin, and extend the survey outward until readings are dry.
Traps that cost marks
Recovering over wet insulation because the surface looked sound. Reusing existing flashings that are already too short for the new roof height. Adding a third shingle layer. Skipping the deck inspection and fastening check before a recover. Ignoring asbestos or lead in the existing assembly before demolition.