Types of Flat Roofing in Southfield: EPDM, TPO and Modified Bitumen
EPDM Rubber Roofing
EPDM is a synthetic rubber sheet, usually black, that comes in large pieces so a garage or small addition often needs few or no seams. It goes down fully adhered with bonding adhesive, mechanically fastened with plates, or loose-laid under ballast. Seams are joined with primer and seam tape. HomeGuide puts EPDM at $4 to $10 per square foot installed and notes it does well in cold climates. InterNACHI estimates its life at 15 to 25 years. Its weak points are seams and the flashing where it turns up a wall.
TPO Roofing
TPO (thermoplastic polyolefin) is a white or light single-ply sheet. Its seams are welded with a hot-air welder, so the joint becomes the same material as the sheet instead of relying on glue. The white surface reflects summer heat, which helps an addition with a living space below. HomeGuide lists TPO at $4 to $10 per square foot installed. InterNACHI's range for it, 7 to 20 years, is a wide one. Ask what membrane thickness the quote is for.
Modified Bitumen (Torch-Down and Self-Adhered)
Modified bitumen is asphalt reinforced with polymer, sold in rolls with a granule surface on the cap sheet. It's usually laid as a two-ply system: a base sheet and a cap sheet. Torch-down rolls are heated with a propane torch to bond. Self-adhered rolls peel and stick, which avoids open flame next to old wood trim on a house. HomeGuide prices modified bitumen at $4.00 to $7.50 per square foot installed. InterNACHI gives it about 20 years.
Built-Up Roofing
Built-up roofing (BUR, or tar and gravel) is layers of roofing felt and hot asphalt topped with gravel. It's the older way to roof a low slope, and plenty of mid-century additions and commercial buildings still carry one. HomeGuide puts new BUR at $3.50 to $7.50 per square foot. Repairs mean scraping back gravel, cutting out the failed area and building it up again in layers. When a built-up roof is replaced on a house, the new roof is usually a single-ply or modified bitumen system.
Flat Roof Repair: Blisters, Seams and Ponding
Most flat roof leaks start at a seam, a flashing turn-up or a spot where water sits. Blisters form when moisture or air gets trapped under the membrane and the sun heats it. Repair is matched to the membrane: a cover strip and seam tape on EPDM, a welded patch on TPO, a torched or adhered patch on modified bitumen. Patching won't solve ponding. If water still stands a couple of days after rain, the roof needs more slope or another drain. HomeGuide lists a roof drain at $70 to $340.
Flat Roofs Over Garages, Porches and Additions
On a house, the flat parts are usually an attached garage, a porch, a sunroom or a rear addition. The tricky spot is the tie-in, where the membrane meets the shingled main roof or turns up the house wall. That joint needs the membrane run up under the shingles and flashed, not lapped on top. HomeGuide puts a 2-car garage flat roof at $1,200 to $4,400. For office, apartment and retail roofs, see commercial roofing.
Why Southfield homeowners call Southfield Elite Roofing
- Free roof inspection
- Written scope and price before work starts
- One local roofing contractor per request
- Southfield homes and buildings only
- No fee for homeowners
Flat Roofing Cost in Southfield
HomeGuide's 2026 guide puts residential flat roof replacement at $3 to $11 per square foot, with tear-off of the old roof at $1 to $2 per square foot. A 1-car garage runs $850 to $3,100 in its figures. These are national estimates, not quotes.
What changes the price:
Membrane and thickness
Built-up and modified bitumen sit at the low end, EPDM and TPO across the middle.Attachment
HomeGuide notes fully adhered systems cost more than mechanically fastened or ballasted ones.Insulation and taper
Tapered insulation to fix ponding adds material but saves the roof.Tie-ins and edges
Wall flashing, metal edge and the joint with a shingle roof take the most labor per foot.
Flat Roof Replacement Process
- 1
Check Slope and Drainage
The contractor checks how the roof falls toward its drains, gutters or scuppers, and marks the low spots where water stands. That decides whether the new roof needs tapered insulation or another drain.
- 2
Check the Deck and Insulation
Wet insulation under an old membrane can't be roofed over. The contractor probes for soft or wet areas so they're in the scope before the tear-off, not discovered during it.
- 3
Tear Off the Old Roof
The old membrane or built-up layers come off, at $1 to $2 per square foot in HomeGuide's figures. Rotted decking gets replaced while it's exposed.
- 4
Insulation and Taper
Rigid insulation boards go down, tapered where the roof needs more fall. HomeGuide lists polyiso board at $0.50 to $3.00 per square foot installed.
- 5
Membrane, Seams and Flashing
The membrane is adhered, fastened or torched in place, seams are taped or welded, and the sheet turns up every wall and curb. The metal edge goes on last, and the joint with any shingled roof is tucked under the shingles.
- 6
Seam Check and Photos
Welded seams get probed along their length. Ask for photos of the seams and the wall flashing, since you probably won't be climbing up to look.
Things to Know About Flat Roofs in Southfield
Code sets a minimum slope. The International Residential Code, the model code Michigan's residential code is based on, calls for a design slope of at least 1/4 inch per foot on built-up, modified bitumen and single-ply roofs. A "flat" roof should still drain.
Shingles stop at 2 in 12. Michigan's residential code doesn't allow asphalt shingles below a 2 in 12 slope, and it requires double underlayment from 2 in 12 to 4 in 12. Many low porch roofs fall under that line, which is why they get a membrane.
Snow sits longer on a flat roof. About 45 inches of snow falls in an average Detroit-area season by NWS normals, and a low-slope roof doesn't shed it. When it melts, the water needs a clear drain or scupper. A drain buried under ice in March leaves the meltwater nowhere to go but the seams.
Coating is a different job. If the membrane is sound but aging, a coating may buy years without a tear-off. See roof coating.