Flat and low-slope roofing
Porches, garages, additions and row-house roofs that are too flat for shingles, done with the right system and proper drainage.
Why a flat roof cannot take shingles
Shingles work by overlapping so that gravity carries water down and off the roof. Below a certain pitch, water moves too slowly and wind can push it back up under the overlaps, so shingles leak. A roof that is flat or nearly flat needs a continuous waterproof surface instead: a roll roofing system for simple low-slope areas, or a membrane on larger and flatter roofs.
In North Jersey these roofs are everywhere once you look: the porch roof on a colonial, the garage or family-room addition off a split-level, the back section of a cape, and the whole roof on many of the attached row houses and two-family homes in Hudson County.
What we install
- Roll roofing for garages, porches, sheds and other simple low-slope sections, where a lower-cost system does the job.
- Membrane roofing for flatter and larger roofs that need a fully sealed surface with fewer seams.
- Edge metal and flashing where the flat roof meets a wall, a parapet or the main shingle roof. Most flat-roof leaks start at those joints, not in the middle.
- Drainage: scuppers, gutters and tapered areas that move water to them, so it does not sit and find a way in.
Which system suits your roof depends on its size, how flat it really is, what is underneath it and how it drains. We will recommend one and explain why.
Ponding water is the warning sign
A low-slope roof that still has puddles two days after rain is telling you something. Standing water speeds up wear on any roofing material, adds weight, and freezes and thaws all winter. Sometimes the fix is a repair at a clogged scupper or a sagging spot; sometimes the roof needs to be rebuilt with better slope to its drains. Either way, it is worth dealing with before it reaches the ceiling below.
For larger buildings with flat roofs, such as townhouse complexes and multi-family buildings, see our commercial roofing page. If part of the roof has just enough pitch, standing seam metal can be another option.
Common questions
How long does a flat roof last?
It depends heavily on the system and on drainage. A flat roof that drains well lasts much longer than one that holds water. Roll roofing on a garage has a shorter life than a membrane on a main roof.
Can you repair a flat roof instead of replacing it?
Often, if the problem is at a seam, an edge or a flashing, and the rest of the surface is sound. If water has soaked the layers underneath, a replacement is usually needed.
Why does my flat porch roof leak where it meets the house?
That joint is the most common leak point on any low-slope roof. The flashing up the wall has to be tied into both the roof and the siding, and it is often the first thing to fail.
How much does a flat roof replacement cost?
It depends on the size, the system, what has to come off and whether the drainage needs rebuilding. See our cost guide.
This page was last updated in September 2026.
Water sitting on a flat roof?
Call (973) 625-7663. Standing water is the first thing we look at.