How does roof pitch affect material choice and installation? It comes down to water runoff, and Flat Roofers NY measures it before recommending anything. Flat and low-slope roofs need one continuous membrane: TPO, EPDM, PVC, modified bitumen or built-up. Steep roofs take overlapping shingle, metal, slate or tile. Each one goes on differently.
Want your slope assessed?
Reading your pitch
Pitch and slope mean the same thing on a job. We measure how many inches the roof climbs over 12 inches of level run. That's written as 4:12, or 1/4:12 on a flat roof.
Manufacturers put the low-slope line at 3:12. Above it is steep-slope. And a "flat" roof still needs about a quarter inch of fall per foot to reach its drain.
Pitch band to material
Find your pitch, then read across. Queens rowhouse main roofs sit in the first row.
| Pitch band | Systems that fit | How it sheds water | Wrong system, what happens |
|---|---|---|---|
|
Flat / low-slope
1/4:12 to under 2:12
Queens rowhouse main roofs |
|
One sealed sheet carries water to drains and scuppers |
Shingles let water back up under the laps |
|
Transitional
2:12 to 4:12
|
|
Laps drain slowly, so the layer underneath works harder |
Shingles on standard felt leak. See repairing a shallow roof with the wrong covering |
|
Steep-slope
4:12 and up
|
|
Gravity pulls water over each lapped unit |
Slate or tile on framing sized for shingles can sag |
How installation changes with pitch
Low roofs seal water out. Steep roofs move it along.
When a flat roof isn't sloped enough to drain
Below minimum slope, water ponds. Puddles left standing 48 hours wear a membrane out early, and ponding can affect the manufacturer's warranty.
You don't need new framing. We lay tapered insulation that falls toward the drains or scuppers. Crickets go behind bulkheads and chimneys to split the flow. That's how we handle clearing standing water with tapered board and crickets.
One building, two pitches
Plenty of Queens buildings carry two pitches. The joint between them gets its own detail.
Membrane runs up under the bottom course. Metal flashing laps over the change in pitch.
The low roof meets the main wall. Membrane turns up the brick, with counter flashing cut in above.
The shallow roof ties into masonry. Reglet flashing seals the joint.
Pitch, warranty, labor and safety
Get your slope assessed
We'll measure it, inspect the roof and tell you which system fits. The estimate is free.
Call (917) 473-9811, or leave your details