Roof Replacement With a Low-Slope Section — Shingles Plus Membrane
Your house has a main roof that takes shingles and a porch, entry or addition roof that is nearly flat, and every leak you have had is where the two meet; you want both done at once and done right at the seam.
Roof replacement with a low-slope section means two roofing systems on one house: architectural shingles on the pitched slopes and a membrane such as EPDM or TPO on the porch, entry or addition roof that is too flat for shingles. JMB Builders replaces both in one job across the Twin Cities metro, with the membrane run up under the first shingle courses so the seam between them does not leak. Priced per project; the low-slope area is its own line.
- Shingles on the pitch, membrane on the flat section
- Membrane runs up under the shingles at the seam
- Low-slope area priced as its own line
- Send photos, reply within one business day
- Licensed MN contractor BC809005
Send photos and hear back within one business day — or book a free in-home estimate.
A lot of metro houses have one roof that is really two. The main roof is pitched and shingled. Somewhere, a front porch, a back addition, an entry canopy or a bump-out over a bay has a roof so shallow that water sits on it. Shingle makers set a minimum pitch, and below it shingles are not allowed because water backs up under the laps. Those sections have usually been roofed with rolled roofing or shingles anyway, and they leak, most often at the line where they meet the steeper roof or the wall above.
The right system for the low section is a single-ply membrane: EPDM, the black rubber sheet, or TPO, the white heat-welded sheet. It goes down over a smooth, dry deck, often with a cover board, fully adhered or mechanically fastened, and turns up the wall or runs up under the shingles above. Where the flat roof dies into the pitched one, the membrane runs well up the slope under the ice and water shield and the first shingle courses, so any water that gets under the shingles lands on membrane. Where it meets a wall, it turns up behind the siding and is covered by counter flashing. Those two seams are the whole job.
We do both roofs in one scope. The shingle roof is the standard tear-off and reroof. The low-slope section is torn off to the deck, the deck repaired or shimmed to drain if it ponds, and the membrane installed and tied into the shingles and the walls. One dumpster, one setup, one permit. The low-slope area is its own line so you can see its share.
What you supply
- Photos of the main roof from the yard and of the flat section from above if you can see it from a window, plus the seam where they meet
- A note about where it has leaked and whether water stands on the flat section after rain
- Your shingle color and your choice of black EPDM or white TPO for the flat section
- Driveway space for the dumpster
What JMB supplies
- Tear-off of both roofs to the deck, with the low-slope deck checked for rot and ponding and repaired or shimmed to drain
- Membrane roof (EPDM or TPO) on the low-slope section with cover board where the deck needs it, fully adhered or fastened
- Membrane run up under the ice and water shield and first shingle courses at the seam, and up the wall under counter flashing
- New drip edge or gravel stop at the low-slope edges, scuppers or a gutter sized to drain it
- The full shingle roof replacement above: ice and water shield, synthetic underlayment, flashing, shingles, ridge vent
- The city's permit and inspection, magnet sweep, finished photos including the seam in your job folder
How it is priced: per project
Quoted in writing from your photos, with a reply within one business day. What moves the number:
- Area of the low-slope section and the membrane type, as its own line
- Deck condition on the flat section; ponding areas may need tapered shims or new sheathing
- Length of the seam to the pitched roof and the walls, which is where the labor is
- Pitch of the low section: a slightly shallow slope may take shingles with full membrane under them instead of a membrane roof
- Penetrations through the flat roof: vents, a chimney, a skylight, each flashed in membrane
- The main roof: squares, pitch, layers, decking, access
Send a photo of the seam where the flat roof meets the house or the pitched roof. That detail tells us most of what the low-slope line will be.
How long it takes
The low-slope section adds half a day to a day to the roof, depending on area and how many walls it meets. Both are done in the same visit so the seam is built once.
How your project works
- 1
Send photos, get a written quote
Send three photos of the space and a sentence about what you want. You get a clear, itemized reply within one business day. Prefer a look in person? A free in-home estimate is always an option.
- 2
Pick materials, or bring your own
We help you choose profiles and materials that fit the house and the budget, or match your existing millwork exactly — or you buy the door or trim yourself and we install it. Everything is confirmed before the crew is scheduled.
- 3
Clean, precise installation
The crew shows up on time, protects floors and furniture, and installs with tight joints and consistent reveals. Photos of the finished work go in your job folder.
- 4
Walkthrough and invoice
We walk the finished work with you. If anything is not right, we fix it before we call the job done. Then one invoice, paid by check or direct deposit — no card fees, no payment links.
Situations and options
Front porch roof
The classic case: a shallow hip or shed roof over the porch dying into the house wall and the main roof. Membrane on the porch, turned up the wall and run up under the main roof's eave courses.
Rear addition roof
A family room or kitchen addition with a nearly flat roof against the back wall of the two-story. Membrane with a cover board, up the wall under new counter flashing, with a scupper or gutter at the low edge.
Shallow but shingle-able section
A section just above the shingle makers' low-slope line takes shingles with ice and water shield under the whole area and a tighter lap. Below the line, it is membrane. We measure the pitch and tell you which.
Entry canopy or bay bump-out
Small flat roofs over a front door or a bay window. Small area, but the seam to the wall is the leak. Membrane turned up behind the siding with counter flashing, tied into the main roof if they touch.
Roof Replacement With a Low-Slope Section — Shingles Plus Membrane: questions, answered
Can you put shingles on a low slope roof?
Only above the pitch the shingle maker allows. Between the standard minimum and the lower limit, shingles can go on over ice and water shield covering the whole section with a tighter course lap. Below that lower limit, shingles are not allowed because water backs up under the laps, and the section needs a membrane roof. We measure the pitch at the estimate and the scope says which system each section gets.
How do you join a flat roof to a shingle roof?
The membrane runs up the pitched slope well past the seam, under the ice and water shield and the first shingle courses, so the shingles lap over membrane and any water that gets under them lands on it and runs back out onto the flat roof. The membrane is adhered to the deck under that lap and never relies on caulk. That seam, and the seam where the flat roof meets a wall, are where most of the labor on the low-slope section goes.
EPDM or TPO for a house addition roof?
Both work. EPDM is the black rubber sheet, glued at the seams and very forgiving in cold; TPO is the white sheet with heat-welded seams that reflects heat. On a small residential section the choice is mostly color and what is visible from upstairs windows: white TPO stays cooler over a room below and shows dirt; black EPDM disappears visually and warms in winter sun. Either is tied into the shingles and the walls the same way.
Why does the flat part of my roof always leak where it meets the house?
Because that is where water runs when it cannot run off: against the wall or against the pitched roof above. On most older flat sections the roofing was stopped at the wall and caulked, or shingles were run onto a slope too flat for them. The fix is membrane turned up the wall behind the siding with counter flashing over it, and run up under the shingles at the pitched roof. Caulk is a maintenance item; a turned-up membrane is a roof.
Water stands on my flat roof after rain, can that be fixed during the reroof?
Usually. Ponding means the deck is low in that spot or the drainage is in the wrong place. During the tear-off we check the deck, replace soft sheathing, and where needed add tapered shims or a tapered insulation board under the membrane so water runs to the edge, scupper or gutter. The membrane itself can sit in water, but a roof that drains lasts longer and the seams stay cleaner.
Do both roofs have to be done at the same time?
No, but the seam between them is built right only when both are open. If the main roof is replaced and the flat section is left, the membrane cannot be run up under the new shingles later without lifting them. If the flat section is done alone, it gets tied in under the existing shingles as best the old roof allows. One visit for both costs less than two and gives a cleaner seam.
Recent JMB work, from our job log
59 installs recorded across 30 Twin Cities communities since Dec 2025. Window and door installs for homeowners, builders and dealers. Counts come straight from our job log; no customer names.
Get a written quote for this job
Three photos and a sentence is enough: a reply within one business day, or ask for a free in-home estimate. Or text the photos to 763-333-4066.
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Read morePage reviewed October 2, 2026 · JMB Builders LLC, MN license BC809005 · All roofing pages
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