The NJ Homeowner's Guide to Flat Roofs

Flat Roofs in NJ

Extremely common on row homes, multi-family buildings, and extensions. "Flat" roofs actually have a slight slope (1/4" per foot) for drainage. Waterproofing and drainage are critical.

Common Materials

TPO: Most popular today. White, energy-efficient, heat-welded seams. 15-25 years, $5-$8/sq ft. EPDM (Rubber): Proven workhorse. Durable and flexible. 20-30 years, $4-$7/sq ft. Modified Bitumen: Multi-layer asphalt. Good for ponding water. 15-20 years, $4-$6/sq ft.

5 Most Common Problems

1. Ponding water — water remaining 48+ hours means inadequate slope or blocked drains
2. Membrane punctures — foot traffic, debris, animal activity
3. Seam failures — UV and thermal cycling weaken adhesion over time
4. Flashing failures — where roof meets walls and penetrations
5. Blistering — trapped moisture expands in heat

Maintenance Schedule

Twice yearly visual inspection. After major storms: check for impacts and ponding. Annual professional inspection after 10 years. Most important: Keep drains clear — a blocked drain on a flat roof can cause catastrophic water accumulation.