Flat & Low-Slope Roofing: what to expect
Why shingles fail on low slopes
Asphalt shingles shed water; they do not hold it back. Below roughly a 2:12 pitch there is not enough gravity to move water off before it finds a lap, and in a Connecticut winter snow sits on a low slope for weeks and melts into every seam. The right answer is a membrane, a single-ply system, a modified bitumen system, or on small areas sometimes soldered metal: that is watertight rather than water-shedding.
Where low-slope roofs actually leak
Rarely in the middle of the field. They leak at the perimeter and at the transitions: where the low slope meets a wall and the counter flashing was never let into the siding properly, at the drip edge, around a scupper or drain, and where the membrane meets the shingled roof above. A useful assessment looks hardest at those junctions.
Drainage and ponding
Standing water is the enemy of any low-slope roof. Ponding accelerates seam failure, adds weight, and in Connecticut freezes and expands. Assessment should include whether the deck has enough pitch, whether tapered insulation is warranted, and whether drains, scuppers and downspouts are actually carrying water off the surface.
Typically included
- Single-ply and modified bitumen membrane systems
- Correct terminations and counter flashing at wall junctions
- Transitions between low-slope and shingled sections
- Drain, scupper and downspout assessment
- Ponding and tapered insulation review
- Porch, dormer, bay and addition roofs