Modified Bitumen Roofing in Dearborn, MI
Read the assembly first when the roof is layered asphalt with a granule-covered cap sheet; the number of plies and whether any are wet is what changes the decision. Modified bitumen is asphalt reinforced with polyester or fiberglass and modified with polymers, installed in sheets that are lapped and bonded. Those laps meet water often in Dearborn, MI, which averages 35.05 inches of precipitation in a year.
A core cut tells us what is really on the roof: the plies, the insulation, the deck and the moisture. The facility director receives the findings in writing, and the repair, recover and replacement paths follow from them.
A core cut is small, a few inches across, and it is patched the same day. It shows the number of plies, the type of insulation, the deck, the thickness of each layer and whether any layer is wet. The core location is marked on the roof plan, and the sample is photographed beside a ruler. Without it, a quote is a guess about what lies beneath the surface. The core also shows whether an earlier recover is buried in the stack, which changes the tear-off and disposal quantities and the code review at the same time.
SBS and APP
SBS, styrene-butadiene-styrene, makes the asphalt rubbery and flexible, which suits climates where roofs cycle through freezing and thawing. APP, atactic polypropylene, makes it more plastic, with good heat resistance and UV stability. Both are made in rolls and installed in layers, and both can be torch-applied, cold-applied with adhesive or self-adhered.
Dearborn's cold season is long, with 4,027 heating degree days at the local station, and SBS flexibility is a reasonable fit for it. The scope names the type and the reason. Reinforcement matters too: polyester gives stretch and puncture resistance, and fiberglass gives dimensional stability.
Torch, Cold-Applied and Self-Adhered Work
Torch-applied sheets are heated at the underside with a propane torch and bonded to the layer below. The work needs a trained crew, fire control and a fire watch afterward. Cold-applied systems use adhesive and avoid open flame, which suits buildings where torches are restricted. Self-adhered sheets are peel-and-stick, with a factory adhesive layer, and are useful in occupied or fire-sensitive buildings.
Each method has trade-offs in speed, odor, weather tolerance and fire risk. Torch work moves fast over clear areas and handles details well in skilled hands, though every detail near a combustible wall or deck needs added protection. Cold-applied work releases solvent odor that can reach air intakes. Self-adhered sheets keep both down but need warm, clean, primed surfaces to hold. The scope identifies the method up front. Hot-work permits, fire-watch periods and insurer requirements are written into the schedule, so the date a torch is lit is never a surprise to the building.
Cap Sheets, Granules and Coatings
The top layer is usually a cap sheet surfaced with mineral granules that shield the asphalt from sun and add fire resistance. Over time granules loosen and wash into the drains, and when bare asphalt shows, the roof is aging faster. We look for granule loss at drains and low areas, blisters, ridging along seams and splits at laps.
Smooth-surfaced membranes are often finished with a reflective coating. An acrylic coating or a silicone coating can extend a sound modified bitumen roof once the surface is cleaned and blisters and splits are repaired. The moisture survey comes first, since a coating over wet insulation traps the water.
Blisters, Ridging and Splits
Blisters are pockets of trapped air or moisture between plies. Small ones that are intact can be watched, and broken ones let water in and need repair. Ridging follows the edges of insulation boards below and indicates movement. Splits at laps and seams show where the roof moved more than the membrane could take.
Repairs use compatible materials and methods. Blisters are cut open, dried and patched, splits are cleaned and covered with new sheet, and flashing is rebuilt with membrane and mastic as needed. A seam failure repair follows a sequence of cleaning, priming and bonding, with attention to the weather at the time of application. Asphalt patches need the right primer, and a patch that does not match the existing system will lift at its edges.
Snow, Hail and Timing
January, with 14 inches of average snowfall in the NWS Detroit normals, is the heaviest snow month, and that is when ice builds at drains and laps. Hail and wind also test a granule surface, and the NWS documented both in Southeast Michigan in September 2026. Hail bruises a granule surface and wind lifts edges, so a post-storm walk looks at both.
Modified bitumen is installed on dry surfaces, and cold-applied adhesives and self-adhered sheets need minimum temperatures to bond. Warm months give the main working window, and any late-fall start comes with a weather hold and a date for the next update. Winter damage from ice dams and drain blockage is common to all roofs, and we recheck seams and flashings after a hard winter. Price tracks how much insulation is wet, how many penetrations and flashings there are, how the sheets are attached, how materials reach the roof and what the building does underneath. Each of those appears as a line in the scope, so a revision can be traced to its cause. We estimate remaining service life from granule loss, cracking and lap condition, and that estimate tells the owner how many years a repair is likely to buy.
Repair, Recover or Replace
Moisture decides. An infrared moisture survey and core cuts show whether insulation is dry. If it is, a modified bitumen roof can often be repaired or recovered with a new membrane over a cover board. If wet insulation spreads across the roof, a full replacement removes the wet material and starts over.
Depending on scope, the permit falls under Michigan's 2021 codes, and the energy provisions may touch insulation. The local enforcing authority confirms what applies before the thickness is set.
Where Modified Bitumen Is Found
Layered asphalt roofs are a possibility on any low-slope commercial building, from Michigan Avenue's East and West Downtown to the Warren Avenue and Dix-Vernor corridors and the Fairlane and Midtown redevelopment the city's audited report describes, and each roof has to be read in person. In the Fairlane and Midtown district and Dearborn Heights the same core-first approach applies, as it does in Detroit and Warren. A comparison with built-up roofing helps where the existing system is unclear.
Commercial Roofing Questions
How do I know my roof is modified bitumen?
A core cut shows the layers. Granule-surfaced rolls with lapped seams are the usual sign from the surface, but only the core confirms the plies and the insulation below.
Is torch-applied work allowed on every building?
No. Some owners and insurers prohibit open flame, so cold-applied or self-adhered systems are used, and the scope states which method applies and why.
What causes blisters?
Trapped air or moisture between plies. Intact ones are watched, and broken ones are cut open, dried and patched, with the location recorded on the roof plan.
Can modified bitumen be coated?
Yes, when it is clean, sound and dry beneath. A coating extends service life and adds reflectance, and the moisture survey comes first.
Why do granules matter?
They shield the asphalt from sun and add fire resistance. Heavy granule loss at the drains means the roof is aging faster than it looks.
Schedule a core cut and inspection
Send what you know of the roof layers, leak locations and access. We will core, test and document the roof, so you can choose between repair, recover and replacement.
