Commercial Flat Roof: Leak Repair or Coating Restoration?

A leak repair is aimed at a failure you can point to. A seam opened, a pitch pan cracked, a drain clamp loosened, a forklift tine went through the membrane. The repair restores that detail and leaves the rest of the roof as it was, good or bad.

A coating restoration is aimed at the whole surface. The membrane is weathered, the seams are tired, the flashings are near the end, and you can see the next leak coming even if you cannot see where. Silicone goes over the entire field after the details are rebuilt, so the roof gets a new continuous waterproof layer without a tear-off.

The mistake runs both ways. Coating a roof that only needed two seams fixed spends capital you did not have to spend. Patching a roof that is failing everywhere means a new service call every storm. The decision comes from the condition of the whole roof, not from the leak that started the conversation.

A coating is only as good as what it is bonded to. That is why the manufacturers put qualification steps in writing. GAF's five-step silicone restoration sheet for EPDM roofs starts with: make sure the roof is clean, dry and tight, perform a moisture scan and identify all wet areas, and conduct an adhesion test. The next step is to replace any wet membrane and insulation with like material.

Mule-Hide's silicone coating specification goes further for its system warranties: a moisture survey report, adhesion tests and a pre-project evaluation must be submitted and approved before installation. Its specification also requires adhesion tests on each distinct roof condition, such as patched areas, previously coated areas and different roof levels.

Coating proposals often lead with the warranty term. The term matters less than what the document covers. GAF's basic limited warranty on its liquid-applied coatings, effective for installs after 1 January 2026, warrants that the coating will not leak because of a manufacturing defect. The remedy is replacement coating for the defective portion, or its cash value. It states that repair of the deck or other materials is not included, that GAF's maximum liability is the original cost of the products, and that it is not transferable.

That same document ties the term to how much coating goes on: a table lists the gallons per square and dry film thickness each product needs for each warranty term, and it says applying less than the listed amount can lead to a denied claim. The product, the rate and the term all belong in your contract.

System warranties are different. Mule-Hide's specification describes 10, 15 and 20 year coating system warranties, available for commercial projects through its eligible contractors, that cover leaks from manufacturing defects, premature weathering and the contractor's workmanship. GAF notes that certain projects installed by its CoatingsPro contractors may be eligible for enhanced warranty or guarantee coverage. Ask which document you are getting and read a sample before you sign.

Michigan's commercial energy code is one more reason the choice between repair, restoration and replacement carries real money. The 2021 Michigan Energy Code for commercial buildings took effect on April 22, 2025, under rules filed by LARA's Bureau of Construction Codes. It adopts the 2021 International Energy Conservation Code with Michigan amendments, and allows ASHRAE 90.1 as an alternative path.

The code treats a full roof replacement as an alteration with an insulation consequence. Section C503.2.1 says roof replacements must meet the code's insulation requirements where the existing roof assembly is part of the building thermal envelope and contains insulation entirely above the roof deck, which describes a typical flat roof with insulation board laid over the deck. It adds that in no case shall the R-value of the roof insulation be reduced as part of the replacement. The code's county table puts Kent, Allegan, Kalamazoo and most of West Michigan in climate zone 5A, and some northern counties, such as Grand Traverse, in 6A. In both zones, Table C402.1.3 calls for R-30 continuous insulation above the deck for most commercial occupancies. On an older building with a few inches of board, that can mean adding substantial insulation, taller curbs and edge metal, and raised flashing heights as part of the job.

A repair or a coating sits differently. Section C503.1 lists alterations that need not meet new-construction requirements, provided the building's energy use does not increase, including roof recover and construction where the existing roof cavity is not exposed. Section C504.1 says ordinary repairs exempt from permit and the abatement of wear due to normal service conditions are not subject to the code's repair requirements. A silicone restoration leaves the existing insulation in place and exposes nothing, which is part of why it can cost far less than a tear-off.

That is not a reason to coat a roof that should be replaced. Wet insulation still has to come out, and replacing it in patches is its own conversation with the building department. But when you compare quotes, ask each contractor whether the scope would trigger the energy code and how much insulation it would require. Confirm how your local building department classifies the work before you sign.

A good repair quote names the failed detail, the materials that will be used to match your membrane, and what the repair is warranted for. A good restoration quote names much more, because there is much more to go wrong.