The situation
The owner had bought the brownstone three years earlier. Previous owner had patched a recurring leak twice without addressing the underlying problem. After a heavy rain event in spring, the patches gave out and water came through the third-floor ceiling. Owner called the contractor who'd done the patches. That contractor quoted another patch.
Owner called us for a second opinion. We walked the roof, found three things:
- The membrane was original modified bitumen from approximately 22 years ago, well past expected lifespan
- The insulation underneath was saturated — we could hear it squelch underfoot, and a core sample came up wet
- The deck at the front parapet showed soft spots; rot had started to spread
This was past repair territory. Patching would have failed within a year, probably less. We recommended replacement and explained why.
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The scope
- Full tear-off of existing modified bitumen, saturated insulation, and degraded cover board
- Deck repair at the front parapet — replaced approximately 18 sq ft of rotted plywood with new 5/8" CDX
- New tapered polyiso insulation at R-25, designed to move water to the existing drains
- High-density gypsum cover board over the insulation
- 60-mil TPO membrane with heat-welded seams
- New aluminum perimeter coping and reflashed parapet walls
- New EPDM at the cornice-to-membrane interface — the historical leak point on most brownstones
- GAF 20-year No Dollar Limit warranty registered to the building, transferable on sale
The timeline
Day 1 (Tuesday): tear-off, deck inspection, deck repair, vapor barrier installed. Roof was watertight by end of day with temporary protection.
Day 2 (Wednesday): tapered insulation, cover board, perimeter detail work.
Day 3 (Thursday): membrane installation, heat-welded seams, perimeter coping, drain reflashing, water test, photo documentation.
Day 5 (Saturday): GAF tech rep inspection for NDL warranty registration. Approved on first inspection.
Day 7 (Monday): closeout package delivered: warranty paperwork, archival photos, contract substantial completion sign-off.
What this cost
Total project cost: $22,400. That included the deck repair (which we identified on the site walk and quoted as a contingency line), the LPC application work for the perimeter coping (Park Slope is in a landmark district), and the NDL warranty registration fee.
The first contractor's "patch" quote was $1,800. By itself that sounds cheaper. But that patch would have failed within a year, the underlying saturation would have continued spreading, and the eventual replacement would have cost more because of additional deck damage. Patching a roof past its useful life is rarely the cheaper choice over a 5-year window.
What the owner said
"Estimate within two days, crew on-site within a week, full flat roof replaced in three days with zero disruption to the tenants downstairs. Pricing matched the quote exactly."
— Sarah H., Park Slope brownstone owner