Flat and Low-Slope Roof Options for Springfield-Area Homes

Why shingles do not work on flat roofs

Shingles shed water because each course overlaps the one below and gravity pulls water down the slope. On a roof with very little pitch, water moves slowly or sits, and it works its way under the laps. The building code sets a minimum slope for asphalt shingles, and anything flatter needs a continuous membrane with sealed seams.

In Springfield, Chicopee and Holyoke, that covers the main roof of most triple-deckers and many brick multi-family buildings, plus countless rear ells, porch roofs and shed dormers on single-family houses.

The three common membranes

EPDM (rubber)

EPDM is a synthetic rubber sheet, usually black, laid in large pieces so there are few seams. It stays flexible in cold weather, which suits a western Massachusetts winter, and it has a long track record on New England houses. Seams are joined with tape or adhesive, and the edges and penetrations need careful detailing.

TPO

TPO is a single-ply plastic membrane, usually white or light gray. Its seams are welded with hot air, which makes them very strong. The light surface reflects sun, so top-floor apartments under a TPO roof tend to run cooler in July. Product quality varies by maker, so ask which brand and thickness is being proposed.

Modified bitumen

Modified bitumen is a modern version of the old tar-and-gravel roof: asphalt sheets reinforced with fabric, laid in one or more layers and often topped with a granulated cap sheet. It is tough underfoot, which helps where a roof is walked on to reach equipment. Some types are torch-applied and some self-adhere; many crews avoid open flame on wood-frame houses.

Drainage comes first

A flat roof is never perfectly flat. It should pitch gently toward a drain, scupper or gutter. Ponding water that sits for days after rain ages any membrane faster and finds every weak seam. During a replacement, tapered insulation or built-up framing can correct low spots, and clogged or undersized drains can be addressed.

Insulation and ice

Many triple-decker roofs have little insulation and almost no air space under the deck. A replacement is the time to add rigid insulation boards on top of the deck, under the new membrane. That keeps heat in the top apartment and reduces the snowmelt that refreezes at the scuppers and gutters in January.

Questions to ask a flat roof contractor

• Which membrane do you recommend for this roof, and why?
• Will the old roofing be torn off down to the deck?
• How will you correct any ponding?
• Will you add insulation, and how much?
• How will you detail the parapets, drains and chimney?
• Do you hold the Massachusetts HIC registration and a Construction Supervisor License?