Built-Up Roofing in Dearborn, MI
A gravel-surfaced low-slope roof on an older commercial building is the classic built-up assembly, and the condition that changes the decision is the number of plies and whether water has traveled between them. A built-up roof is made of alternating plies of reinforcing felt and bitumen, topped with gravel, a mineral cap sheet or a coating. Dearborn, MI, recognizes four business districts, East Downtown, West Downtown, Warren Avenue and Dix-Vernor, and a roof in any of them must be read in person before a fix is proposed.
We count the plies with a core cut, identify the insulation and deck, locate the surface type and record any layers that may be wet. That record tells the owner whether to repair, recover or replace, and what each choice costs.
How the Layers Work
A BUR assembly starts with a base sheet or insulation, then adds plies of felt bonded with hot asphalt, coal tar or cold adhesive. Multiple plies mean redundancy: a defect in one layer is covered by the next. The surface may be gravel embedded in bitumen to protect against sun and add fire resistance, a mineral-surfaced cap sheet, or a smooth surface with a reflective coating.
Gravel hides the membrane, which makes inspection harder. Low areas, flashing and blisters can be buried under stone. On a gravel-surfaced roof, we sweep selected areas clear, photograph what is under them and note where the stone has migrated to the drains. Gravel in a drain bowl is a leak waiting to happen, and the sweep also lets us check flashing bases for splits.
Some built-up roofs carry a smooth surface with an aluminum or white coating instead of gravel. Those roofs are easier to read and show blisters and cracking directly. The coating itself ages, chalks and thins, and a recoat plan is part of a maintenance program. Without it, the bitumen below is exposed to sun and weather again, and the roof ages from the top down.
Aging Signs and Failure Patterns
Built-up roofs fail in recognizable ways: alligatoring of the surface, blisters that break, ridges over insulation joints, splits in the membrane at changes in plane and flashing that has pulled away from walls. Pitch-based surfaces can flow in summer and crack in winter, and asphalt can oxidize and lose flexibility.
With 4,027 heating degree days and a 49.5 degree annual mean at the Dearborn station, every season moves the membrane by a measurable amount. Splits often open along the lines where the roof moved most, such as the edge of a deck panel, a change in insulation thickness or the line where an addition meets the original building. We map them on the roof plan, photograph each from a fixed point and measure the length, so the repair decision rests on numbers.
Moisture Between the Plies
Water that enters a multi-ply roof can travel between plies and into insulation before it reaches a ceiling. The wet area is often far from the visible defect. An infrared moisture survey maps the wet area, core cuts confirm it, and the boundary becomes the repair limit.
Repair within the boundary can involve removing wet insulation and patching the plies back in. Beyond a certain extent, repairing a built-up roof piece by piece costs more than replacing it. The scope compares both, with the cost of each and the expected life of the result. Foot traffic matters too: a built-up surface under rooftop equipment that gets frequent service wears faster along the paths to it, and walkway pads laid over the route extend the life of the surface. Remaining service life, judged from cracking, blistering and the condition of flashings, goes into the written findings.
Hot Asphalt, Fumes and Safety
Traditional BUR installation uses a kettle or tanker of hot asphalt on or near the roof. The work requires fire controls, a trained crew, ventilation planning and communication with the building about fumes. Air intakes near the work area are closed or filtered, and the schedule tells tenants when odor is likely. Cold-process adhesives reduce heat and odor and suit buildings where hot work is restricted. Material is hoisted in the morning and the kettle, if one is used, is placed away from air intakes, walkways and combustible walls, with the fire-safety plan reviewed at the start of each day.
Not every building allows hot work, and some insurers restrict it. Where it is allowed, a fire watch stays on the roof for a set period after the last application, and extinguishers and clear access are checked before work starts. If the building is occupied, the schedule and the odor plan go to the facility director before the roof is opened.
Snow, Rain and the Installation Window
The Dearborn station records 35.05 inches of precipitation a year, including 30.8 inches of snowfall, and the NWS Detroit record puts the first measurable snow around November 16. Built-up work needs dry, warm days, because bitumen applied in cold or damp conditions does not bond well. A late-season start risks cold plies and incomplete flood coats, so the schedule carries a weather hold and a clear rule for stopping.
After installation, drainage is the first protection. Gravel stops, scupper details and drain bowls get checked after the first heavy rain and again after the first thaw. Heavy snow adds weight to a roof that already carries a gravel surface, and project snow loads require code-specific site checks before layers or ballast are added.
Repair, Recover or Replace
A built-up roof with dry insulation and a sound deck can often be restored with a coating or recovered with a single-ply membrane over a cover board. Permitted work follows Michigan's 2021 building and energy codes, and reviewers care how many layers already sit on the roof. Where the roof already carries multiple layers, a full replacement removes them.
Single-ply replacements such as TPO or a modern modified bitumen system are common after a tear-off. The choice depends on exposure, budget and the building's tolerance for noise, odor and heat work. Wet insulation is often the real cost driver, and we state the wet area in square feet from the survey and price each path.
Where Built-Up Roofs Appear
Older low-slope commercial buildings are the usual place for built-up roofs, and Dearborn's older commercial streets, from Michigan Avenue's East and West Downtown districts to the Warren Avenue corridor and the South End's Dix-Vernor corridor, are where a core cut settles the question. In West Downtown Dearborn and the Dix-Vernor corridor the work starts with that cut, and so it does in Detroit and Southfield.
Commercial Roofing Questions
How many plies does a built-up roof have?
A core cut shows it. Two to four plies is typical, and the count affects repair and replacement choices as well as the cost of tear-off.
Why is gravel a problem for inspection?
It hides the surface. We sweep selected areas clear and photograph what is under them, then put the stone back or remove it as the scope directs.
Can a BUR roof be coated?
If it is clean, sound and dry beneath, yes. A coating adds reflectance and protection, and a recoat plan keeps it protective.
What makes tear-off of a BUR roof expensive?
Weight, layers and disposal. Multiple plies of felt and bitumen are heavy and slow to cut away, and wet insulation adds to the volume.
Is hot asphalt required?
No. Cold-process adhesives and other systems exist. Building rules and insurer limits guide the choice, and the scope states it.
Schedule a core cut and inspection
Send any drawings, past repairs and leak locations. We will core, test and document the roof, so you can choose between repair, recover and replacement.
