Coating, recover or replacement?

Stop conditions for coating

Our feasibility check will not present coating as the recommended solution if you report any of these: wet insulation, a damaged or unsafe deck, repeated leaks with no known source, widespread membrane or seam failure, a failing or incompatible existing coating, unresolved ponding or blocked drains, or widespread rust or fastener failure on metal. Unknown answers mean professional review.

Before anyone quotes a coating

• A moisture survey, with cores to confirm the readings.
• Adhesion tests on the existing surface.
• A named manufacturer system, with its preparation, primer, coats and coverage rates.
• A drainage plan, and repairs to seams, flashings and penetrations.
• Warranty terms, and who inspects and issues the warranty.

What our winters do to a low-slope roof

The biggest enemy of a flat roof between Toledo and Flint is not summer heat. It is water that gets in during the shoulder seasons and then freezes. A small open seam in October lets water into the insulation, and months of freeze and thaw widen the gap and spread the wet area. By spring the same roof can have a leak inside and a soft, saturated section that no coating can bond to. That is why the first question for any coating bid here is how much of the roof is wet right now.

Snow matters too, even though northwest Ohio and southeast Michigan sit outside the heaviest lake-effect snow belts. NOAA's Great Lakes lab notes that lake-effect snow depends on wind direction, which is why the snowiest bands fall downwind of the lakes in places like west Michigan and the area east of Cleveland. Our region still sees steady snow cover. Snow drifts against parapets, rooftop units and step-downs, holds meltwater at blocked drains and hides ponding until it refreezes. Any coating, recover or replacement plan should include where snow piles up and whether the drains and scuppers can move the melt.

Ponding water is the other local problem. Many buildings in the region have flat, old roofs over large footprints, where a little deck deflection adds up to low spots. Water that sits for days in summer freezes into ice sheets in winter. Before coating, map ponding after a rain and ask whether the plan fixes it with drains, crickets or tapered insulation.

The coating season in Ohio and Michigan

Coatings are liquid products that need the right weather to go on and cure. Many manufacturer data sheets call for air and surface temperatures of at least 40°F, a surface at least 5°F above the dew point, and no rain, dew or frost during application. In practice, that makes late spring through early fall the working season here. October can work on dry, sunny days, but morning dew, short days and cold nights narrow the window fast.

A practical calendar for an owner or board:

• Late winter: gather roof history, warranties, leak logs and the last inspection report. Budget and board approvals usually take longer than the work.
• Spring, after snow melt: inspect, core-cut and run a moisture survey while winter damage is fresh and visible.
• Late spring: decide coating, recover or replacement per section, then get comparable bids on the same scope.
• Summer: schedule the work. Schools often target summer break, and churches often work around weekend services.
• Fall: clean drains and check flashings before the first freeze, whatever path you chose.

When code rules out a recover

Ohio's 2024 building code, in effect since March 1, 2024, and Michigan's current building code, in effect since April 9, 2025, are both based on the 2021 International Building Code with state amendments. The model code's reroofing section does not allow a roof recover when:

• the existing roof or roof covering is water-soaked, or has deteriorated to the point that it is not an adequate base for more roofing;
• the existing roof covering is slate, clay, cement or asbestos-cement tile; or
• the existing roof already has two or more applications of any type of roof covering.

That means a building that has already been recovered once is usually headed for a full tear-off. Replacement can also bring energy-code insulation requirements into play. Ask your designer or contractor what the job triggers, and check with the local building department whether your city requires a permit for a coating, a recover or a replacement. Practices vary from city to city.

Planning numbers (our provisional settings)

For early budgeting only, our commercial roof cost planner uses these owner-set settings. They are not a market average, observed local pricing or a quote.

Wet insulation removal, deck repair, drainage changes, rooftop unit curbs, access, warranty level and the season all move real bids. Only an inspection and written proposals set a price.

How buildings in our region usually sort out

Warehouses and plants along I-75, I-280 and the Ohio Turnpike often have large metal or single-ply roofs where a coating can make sense on the dry areas, once fasteners, seams and rust are dealt with. Office and light-industrial buildings along I-696, I-96 and I-275 in metro Detroit tend to have single-ply roofs from the 1990s and 2000s. Many of those are now at the age where a moisture survey decides between restoration and replacement. Churches and schools often have several roof sections of different ages and systems on one campus, so the right answer is usually different for each section. HOA and condo communities with flat-roof clubhouses or carports face the same choice at a smaller scale, with the added step of a board vote and a reserve plan.

A five-step way to decide

1. Collect what you know: roof age, system, warranty, past repairs and every leak with its date and weather.
2. Get a moisture survey with core cuts, section by section.
3. Remove or replace the wet areas first. A coating over wet insulation traps the water.
4. Check the rules: layer count, code limits on recovers, permit needs and the manufacturer's requirements for the coating warranty.
5. Compare options over the same time frame, including the maintenance each one needs. Our coating feasibility check screens out the obvious stop conditions first.

Detroit permit records

In the Detroit building-permit export we reviewed, explicit coating language is rare. Our rules found one permit description that mentions fluid-applied roof coatings and a few dozen that describe a roof recover or overlay. These are provisional rule matches, not verified projects, and permit dollar fields are not installed prices. See the research page.

Sources

1. 2021 International Building Code, Section 1512.2.1 Roof recover, International Code Council.
2. Ohio Board of Building Standards 2024 code update information, City of Toledo.
3. 2024 Ohio Building Code, preface, International Code Council.
4. 2021 Michigan Building Code, International Code Council; and code books, Michigan LARA Bureau of Construction Codes.
5. Parts of the Great Lakes are the snowiest places in the U.S., NOAA Great Lakes Environmental Research Laboratory; and What is lake effect snow?, National Weather Service.
6. Silicone SP guide specification, Neogard; and Unisil silicone roof coating data sheet, GAF. Examples of published application limits; always follow the data sheet for the product on your bid.

Guides: Silicone coatings · Roof recover · TPO · EPDM