Flat Roof Replacement for Philadelphia Rowhomes
A flat roof that holds water, leaks in new places every season, or carries layer on layer of old roofing is past repair. We take it down to the deck, fix the drainage, and install a membrane suited to your roof.
Replacing a Philadelphia rowhome flat roof means a tear-off to the deck, new insulation or tapered board where water has been ponding, and a new EPDM, TPO or modified bitumen membrane. Recent Philadelphia figures put rowhome flat roofs at $6 to $11 per square foot installed, depending on the membrane and the prep the deck needs.
Signs the Flat Roof Is Done
Replacement is the honest answer when water sits across large areas two days after rain, when the membrane is brittle and cracks where you step, or when leaks keep appearing in new places. Soft spots underfoot mean the deck below has been wet for a while.
The payoff of a full replacement is fixing what caused the old roof to fail. That usually means drainage: slope that was never built in, or a deck that has sagged since. Membranes we install include systems from Firestone, Carlisle, Johns Manville and GenFlex, chosen to suit the roof rather than the label.
What Sets the Price of a Flat Roof Replacement
- Roof areaRowhome roofs are small, so setup is a bigger share of the cost.
- Layers and tear-offEach old layer adds labor and disposal.
- Membrane choiceEPDM, TPO and mod bit price differently.
- Drainage workTapered insulation, crickets and drain resets add material.
- Parapets and additionsCoping, party-wall seams and extra roof levels add detail work.
Published 2026 Philadelphia figures put rowhome flat roof replacement at $6 to $11 per square foot installed. Those are market planning ranges, not our quote.
EPDM, TPO or Modified Bitumen?
All three work on a rowhome. The differences are in the seams, the surface and the price.
| Membrane | Seams and surface | Published Philadelphia range |
|---|---|---|
| EPDM rubber | Black sheet, glued and taped seams, long local track record | $6 to $9 per square foot |
| TPO | White reflective sheet, heat-welded seams | $7 to $10 per square foot |
| Modified bitumen | Torched or self-adhered, usually with silver coating | $3.50 to $4 per square foot |
Tear-Off of Built-Up and Layered Roofs
Many older rowhome roofs carry a built-up tar and gravel roof under one or two layers of rolled roofing or modified bitumen. Once two layers are up, the city requires a full tear-off, and on a flat roof it is the only way to find wet insulation and rotted planks. We remove everything to the deck, cart it off in the same day's work, and replace soft boards before any new layer goes down. Published Philadelphia figures put the tear-off at $1.50 to $3 per square foot on top of the new roof.
Tapered Insulation for Drainage
Ponding is the main reason flat roofs fail early, and the cure is slope. Tapered insulation boards are cut thicker at the high end and thinner at the drain or scupper, building a fall into the roof without reframing it. Small crickets between drains stop water collecting in the low valleys that form between them. On most rowhomes this also adds insulation over the top floor, which is usually the hottest room in the house in summer and the coldest in winter.
Parapet and Coping Tie-In
Rowhome roofs end at parapet walls, and the membrane has to run up the wall and under the coping to stay watertight. On a replacement we strip the old flashing from the parapet, run new membrane up the inside face, and cap the wall with new metal coping or reset the existing stone. Where our roof meets a neighbor's at the party wall, the seam is sealed so water cannot cross between the two. Deteriorated parapet brick gets flagged, and our parapet and coping repair covers that work.
Rear Addition and Porch Roof Sections
Many rowhomes have a lower rear addition or kitchen roof and a front porch roof, each with its own membrane and each tied into a wall of the main house. They are often in worse shape than the main roof because they collect runoff from above. On a replacement we redo them with the main roof so all the tie-ins are new at once. Published figures put a rear flat section added to a pitched-roof replacement at $2,000 to $4,000.
Brands we install and service
Tired of patching the same flat roof?
Call and we measure it, check the deck and price all three membranes.
What We See on Philadelphia Roofs
The late-1950s rowhomes of Morrell Park are about 1,200 square feet with front garages, so their flat roofs are small and simple, and replacement there is mostly about the tear-off and the drain. Mayfair's larger rows, laid out with rear garages, often carry a separate low roof over the back that fails first. Across the city, a roof already carrying two layers has to come off to the deck before a new one goes on.
How a Flat Roof Replacement Runs
- 1
Measure and core
Area measured, layers counted with a small core cut.
- 2
Pick the membrane
EPDM, TPO or mod bit priced side by side.
- 3
Permit and materials
L&I permit filed, materials hoisted to the roof.
- 4
Tear-off and deck
Old roof off, soft boards replaced the same day.
- 5
Slope and membrane
Tapered board, cover board, membrane and parapet flashing.
- 6
Drains, coping, cleanup
Scuppers, coping and neighbor seams finished, debris gone.
Flat Roof Replacement Questions
Most rowhome flat roofs are done in one to two working days. Rear additions and extra layers can add a day.
Only over a single sound layer with a dry deck. With two layers up, the city requires a tear-off.
There is no single best. EPDM has the longest local track record, TPO reflects summer heat, and mod bit takes foot traffic well.
Yes. The party-wall seam is part of the job, sealed so water cannot pass between roofs.
No. Cover furniture under the roof hatch and near walls; tear-off shakes loose some dust.
More Replacement & Installation Work in Philadelphia
From our guides: What a Roof Replacement Costs in Philadelphia
Replace the Flat Roof and Fix the Drainage
Call for a measured quote on all three membranes. We fix the slope along with the roof.