Flat Roof Replacement Cost in Michigan: EPDM, TPO, Coatings

The calculator at the top of this page prices shingle roofs. Flat and low-slope roofs price differently, so set it aside. By the national cost guides, a residential flat roof replacement runs about $4 to $8 per square foot installed for modified bitumen, $4 to $13 for EPDM rubber and $4 to $14 for TPO, with a typical whole job between $4,000 and $21,000. A silicone coating over a sound existing roof runs roughly $1.50 to $4.50 per square foot. Those are national figures, not our prices, and we say so whenever a number below is ours. I'm Aaron Scott, a licensed Michigan residential builder and the owner of Roofing Army, and what follows is how we price and build these roofs.

How Much Does a Flat Roof Replacement Cost in Michigan?

The per-square-foot ranges below come from a national home-services cost guide updated in January 2026, with coating ranges from a second national guide. The lifespans for modified bitumen, EPDM and silicone are the ones we publish on our own roof replacement page; the TPO figure is the national guide's, since we do not install TPO on homes.

To make that concrete, a 400 square foot porch roof in modified bitumen at $4 to $8 per square foot works out to $1,600 to $3,200, and a 600 square foot garage in EPDM at $4 to $13 works out to $2,400 to $7,800. That is arithmetic on national ranges, not a quote. The low end of each range is a simple overlay with no insulation work; the high end is a full tear-off with new insulation, edge metal and flashings. Small roofs also cost more per square foot than large ones: permit, dumpster and crew setup cost about the same at 400 square feet as at 4,000. Our published shingle jobs show the same pattern (see our Michigan roof replacement cost guide), so a high per-square-foot number on a small porch roof is not by itself a red flag.

Which Flat Roof System Do We Install on Michigan Homes?

About 8 percent of the replacement quotes in our CRM include a low-slope or flat section, and flat or low-slope sections were the reported leak source on 63 of our logged leak calls, behind only water getting behind the gutter, wall flashing and chimneys. Most are porch roofs, additions and garages on otherwise shingled homes. We install three flat roof systems:

• Modified bitumen. Asphalt-based rolled roofing reinforced with rubber or plastic polymers and finished with a granulated cap sheet. Our standard for porches, additions and low-slope sections that tie into a shingle roof. We install CertainTeed Flintlastic.
• EPDM rubber. A single-ply synthetic rubber membrane installed in large sheets with very few seams. It stays flexible through Michigan winters. We use it on garages and large flat sections.
• Silicone coatings. A fluid-applied coating that cures into a seamless, reflective waterproof layer over an existing flat roof. It extends the life of a structurally sound roof without a tear-off and stands up to ponding water. We use it on commercial and industrial flat roofs.

TPO is in the table because homeowners ask about it: a white thermoplastic membrane with heat-welded seams, common on commercial buildings.

What Moves the Price of a Flat Roof Replacement?

Tear-off versus overlay

The Michigan Residential Code defines a roof replacement as removing the existing roof covering down to the deck. A recover, meaning a new membrane over the old one, is allowed only where the manufacturer's instructions permit it, and never where the existing roof is water soaked or deteriorated, or where there are already two or more layers of any roof covering. The national guide puts tear-off at $1 to $5 per square foot. An overlay saves that but hides what is underneath, usually wet insulation, so we lean toward a full tear-off on anything that has leaked.

Insulation and tapered insulation

The code requires a design slope of at least one quarter inch per foot for new modified bitumen, EPDM, TPO and liquid-applied roofs. A reroof is exempt if the roof already drains positively, but a roof that holds water now will hold it under the new membrane. Tapered insulation, rigid foam cut on a slope to push water toward the drains, is how a dead-flat roof gets pitch. It is the biggest reason two quotes for the same flat roof can be thousands apart. Ask whether it is included and what slope it builds.

Drains, scuppers and edge metal

A flat roof sheds water through drains, scuppers through the parapet, or over a drip edge into a gutter. The code requires existing flashings, edgings, outlets and vents to be replaced when rusted, damaged or deteriorated, so new edge metal and drain parts belong in the quote. Gutters are not our work; we refer that to our gutter partner.

Parapet and wall flashing

Where the membrane meets a wall or parapet it has to turn up, terminate and be counterflashed. Wall and step flashing was the second most reported leak source in our CRM, and on flat roofs it is where most of the labor goes. Long wall runs and masonry parapets cost more than a simple drip-edge perimeter.

Tie-ins where a low-slope section meets a shingle roof

Porch and addition roofs usually tuck under a shingle slope, and the membrane has to run up under the shingles far enough that runoff cannot get behind it. In winter, meltwater off a poorly ventilated slope above refreezes on the colder flat section, the same mechanism behind ice dams in Southeast Michigan. If the attic above is the problem, fixing the attic ventilation during the job protects the new flat section too.

Decking repair

Flat roofs that leaked for years often have soft spots in the deck, and nobody sees them until the old roof is off. Get a per-sheet price for replacement decking in writing before the job starts. Our guide on rotted decking and sagging roofs covers that repair.

How Long Does a Flat Roof Last in Michigan?

Michigan is hard on flat roofs for three reasons: freeze-thaw, snow and standing water. Water that gets into a seam or flashing lap freezes and pries the joint open a little further every cycle, snow sits on a flat roof instead of sliding off, and any spot that ponds stays wet long after the rest of the roof is dry.

EPDM handles the cold well: the EPDM Roofing Association, cited by a major membrane manufacturer, reports a brittleness temperature of minus 49 degrees Fahrenheit under ASTM D746, far below anything Michigan sees. Modified bitumen is the system we see wear out soonest, as the granulated cap sheet sheds granules and dries out over 15 to 20 years.

Ponding is the one to watch. A puddle the day after a rain is normal; water still standing two or three days later is ponding, and that area will fail first whatever the membrane is. It needs tapered insulation or a drain, not just a new surface.

When Is a Roof Coating a Smart Fix, and When Is It a Bad Idea?

A coating is the right call when the existing roof is structurally sound and dry, the leaks are at seams and flashings rather than across the field, and you want 10 to 20 more years without the cost and disruption of a tear-off.

It is a bad idea when the roof is wet underneath. Coating manufacturers require a moisture survey first, call for wet insulation to be removed and replaced, and say not to coat over saturated insulation at all. A facilities-management trade publication puts it bluntly: if the roof is more than 25 percent wet, do not spend the money on a coating. A coating over wet insulation seals the water in, and the roof keeps rotting under a bright white surface.

Chronic ponding is the other disqualifier. As one manufacturer's representative put it, consistent ponding water means there is an underlying issue that must be addressed before coating. Silicone tolerates standing water far better than acrylic, which is why we use silicone, but even silicone makers call for adhesion testing and often a primer in ponded areas. Acrylic in standing water can soften, curl or peel, so an acrylic proposal on a roof that ponds is a reason to keep shopping.

Our guide on repair versus replacement in Michigan walks through the same decision for the whole roof. For an active leak on a flat section, roof repair can often fix a seam or flashing without touching the rest, and emergency tarping buys time after a storm.

How Do You Read a Flat Roof Quote?

A flat roof quote should be specific enough that two contractors could build the same roof from it. Look for:

• The system by name and thickness. Mils for EPDM or TPO; base sheet and cap sheet for modified bitumen. "Rubber roof" is not a specification.
• Tear-off or overlay, stated plainly, with the layers assumed and what happens if more are found.
• Insulation type and thickness, and whether it is tapered and to what slope.
• Decking replacement price per sheet, in writing, before the job starts.
• Edge metal, drains and scuppers: new or reused, and which.
• Wall and parapet flashing: how high the membrane turns up and how it is terminated.
• The tie-in detail where the flat section meets the shingles, including how far the membrane runs under them.
• Permit, dumpster and cleanup in the number (see our roof permit guide).
• Both warranties in writing, with the actual years. Ours is 50 years on workmanship.
• Payment terms. We do not take deposits; you pay when the work is done and you are satisfied.

Our guides on what a roof replacement quote should include and how to compare roofing quotes cover shingles, but the rule is the same: compare line by line, not bottom number to bottom number.

Get a Real Number for Your Flat Roof

National ranges are a starting point. Your porch, addition or garage roof has one exact price. Our inspections are free, and we give every customer five quotes at different price points so you can see the real tradeoff between an overlay, a tear-off and a coating where one qualifies. A Roofing Army project manager is on site for every job, our crews are in-house, and every project in our job gallery shows its real price alongside the drone photos customers see in their portal. Financing can spread the cost; get the itemized price first. We serve Southeast and West Michigan, including Ferndale, Royal Oak and Plymouth, from five local offices.