‍The Old Asphalt Flat Roof Nobody Talks About. But Everybody Has.

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Modified bitumen and built-up roofing systems, mod bit and BUR, are the workhorses of the commercial roofing world in Northwest Indiana. Strip malls in Merrillville. Office buildings in Crown Point. Older industrial facilities in Hammond. If the building was put up before 2000, there is a strong chance it has one of these systems.

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They are not glamorous. They are not TPO white. They are black, they are heavy, and when they fail, they fail in ways that most contractors either miss or handle wrong. Here is what you actually need to know.

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5 Things That Go Wrong on Mod Bit and BUR Coating Jobs

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1.  Coating too soon after installation.  New modified bitumen and BUR contain light oils that must leave the membrane before any coating is applied. The minimum aging time is 90 days. Coat it before then and the oils will bleed through, staining the coating, destroying adhesion, and voiding the warranty. Most contractors do not mention this rule.

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2.  Skipping the stain blocker.  Even fully aged asphalt retains enough oil to cause staining and adhesion failure. A stain-blocking coat is required before the main coating system goes down. This is not optional. It is chemistry. Skip it and you will see brown bleed-through within the first season.

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3.  Ignoring granule adhesion on modified bitumen.  Granulated surface mod bit presents a coating adhesion challenge. The granules themselves must be properly embedded and stable before coating. Loose granules under a coating layer create delamination.

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4.  Treating gravel-surfaced BUR like a smooth surface.  It is not. Gravel presents significant coating problems. You cannot simply pour coating over gravel until it is covered, the resulting thickness creates cracking, never fully dries, and adds enormous weight to the assembly. Gravel must be addressed before coating begins.

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5.  No moisture scan.  BUR systems are multi-ply felt and asphalt assemblies that trap moisture between layers invisibly. The surface can look intact while water is migrating through the plies. A moisture scan, and core cuts if needed, is not optional on a BUR restoration job.

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Dad joke break: What did the BUR roof say to the new coating? "You need to let me age a little first. I've got oils. I've got layers. I've got history. Give it 90 days."

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Granulated vs. Smooth Mod Bit — Different Rules

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The surface type determines the approach:

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Smooth Surface

Granulated Surface

Easier adhesion surface

Granule stability must be verified first

Stain blocker required

Stain blocker required

No primer needed typically

Primer required for 20-yr silicone systems

Acrylic or silicone system

Acrylic, SEBS, or silicone — surface-dependent

3.0 gal/sq minimum (acrylic)

3.0–3.5 gal/sq (acrylic); 2–2.5 gal/sq (silicone)

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The Mod Bit / BUR Restoration Sequence

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A.  Age verification. When was the roof installed or last re-surfaced? Less than 90 days ago? Do not coat it yet. Wait, or recommend the building owner wait.

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B.  Moisture scan. Core cuts if needed. BUR traps water. Find it.

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C.  Full chemical clean. 115 Cleaner. Rinse. Dry. Asphalt roofs in industrial environments carry heavy contamination.

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D.  Stain blocker application. Every mod bit and BUR job. No exceptions.

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E.  Pipes, vents, AC units, rooftop units, individually addressed and flashed.

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F.  Seam and flashing reinforcement, mesh embedded in primer or base layer.

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G.  Base coat at 1.5 gal/sq. Finish coat at 1.5 gal/sq. Total system 3.0 gal/sq minimum.

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H.  20-year NDL warranty filed.

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Serving These Northwest Indiana Cities for Mod Bit & BUR Restoration

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Hammond  •  Gary  •  East Chicago  •  Whiting  •  Portage  •  Merrillville  •  Crown Point  •  Valparaiso  •  Michigan City  •  Chesterton  •  Highland  •  Munster  •  Dyer  •  Lowell  •  St. John

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Get a Free Commercial Roof Assessment

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No pressure. No pitch. Just an honest look at what your roof actually needs.

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pristineindustrialroofing.com

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Pristine Industrial Roofing  |  Conklin Preferred Contractor  |  Northwest Indiana

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