The porch, the addition, the flat run behind the dormer — the parts too low-sloped for shingle to work. We cover them with base-and-cap bitumen or heat-welded TPO.
Most Grand Valley houses have at least one section that isn't steep enough for shingle. Here's why that section behaves differently — and what actually belongs on it.
Water has to run off a shingle roof faster than it can work sideways under a lap. Below a certain pitch it simply can't, and wind-driven rain pushes it back uphill. That's a physics problem, not an installation problem — no amount of careful shingle work fixes it.
A base sheet bonded down, a granulated cap sheet over the top of it, and the seams sealed so the whole section becomes one continuous surface. You'll hear it called modified bitumen, and it's the system we put on the flat sections of otherwise-shingled roofs.
The membrane rolls out and the seams are welded with heat rather than glued, so the joint ends up as strong as the field around it. Nothing up there is depending on a bead of sealant still being flexible in ten years.
Where the steep section meets the flat one is the most common failure point on a house that has both — and the detail most crews move through fastest. Done right it's flashed and lapped so water crossing from one system to the other never gets underneath. If yours is already leaking, that joint is the first place we look.
A low-slope surface takes near-perpendicular summer sun for more hours a day than a pitched slope does. On the Western Slope, UV is the clock on a membrane — not snow, and not cold.
Drains, scuppers, and enough pitch to actually reach them. When a monsoon burst drops an inch in twenty minutes, you find out quickly whether your flat section drains or just holds it.
Seeing water sit up there, or a stain on the ceiling under the flat part? That's what the free inspection is for — and if the section is sound, we'll tell you that too.
Base and cap bitumen is the workhorse for the low-slope sections of a shingled house — a porch, a dormer run, an addition. It's tough underfoot, it patches cleanly years later, and its granulated surface sits comfortably next to shingle.
TPO membrane makes more sense on a larger uninterrupted flat area, where one welded sheet beats a lot of overlapping courses, and where a lighter-colored surface reflecting summer heat actually changes what's underneath it.
We'll get on it, tell you which system your section calls for, and put it in writing. If the flat part is failing but the shingle is fine, that's worth knowing before anyone quotes you a whole new roof — a flat roof repair is often the whole job.
Roughly speaking, anything too shallow for shingles to shed water reliably — the porch roof, the run over an addition, a dormer connector, sometimes a whole garage. It doesn't have to look flat to behave flat. If you're not sure which category yours falls in, that's a thirty-second answer once someone is up there.
Shingles work by shedding water downhill fast, and every course depends on gravity beating capillary action and wind. Below a certain pitch that stops being true — water creeps under the laps and sits. Plenty of low-slope sections out there do have shingles on them; they're usually the part of the roof that keeps leaking.
It changes a fair bit, and around here it's common. A cooler means someone is up on that section every spring and fall, so it wants a surface that tolerates being walked on and a defined path to the unit rather than a new route each time. It also means a water line and a pan sitting up there for half the year — and a leak under a swamp cooler is very often the cooler rather than the roof. We'll tell you which one you've got before anyone sells you roofing.
Usually yes, and often that's exactly the right call — the low-slope part frequently wears out well before the shingle around it. The one thing that has to be done carefully either way is the transition where the two systems meet.
Short-lived puddles after a hard rain aren't unusual. Water that's still there days later is telling you something — about pitch, about a blocked drain or scupper, or about a low spot that's developed. It's worth a look, because standing water finds the weakest seam eventually.
Yes. It's the same family of systems, but a building brings different logistics — tenants, roof access, and rooftop equipment — so it has its own page.
See commercial roofing →We'll get on the low-slope section, photograph what we find, and tell you plainly whether it needs a repair, a recover, or nothing at all.
