A proven commercial system, but aging modified bitumen portfolios require close attention to avoid compounding problems.
Modified bitumen (mod-bit) is an asphalt-based roofing system applied in layers and reinforced with polyester or fiberglass. It is common on commercial buildings constructed between the 1970s and 2000s, particularly in multifamily, institutional, and industrial applications. Modified bitumen is durable and repairable, but aging systems across Virginia frequently show blistering, cracking, seam separation, and flashing failures that require systematic attention rather than reactive patching.
Blistering — Trapped moisture or air between layers creates blisters that rupture and allow water infiltration.
Surface cracking and alligatoring — UV degradation over time causes the surface to crack in a pattern that accelerates moisture penetration.
Seam and lap failures — Torch-applied or cold-applied seams separate, particularly at perimeter flashings.
Flashing deterioration — Metal and bitumen flashings at walls, curbs, and penetrations are the most common failure point on older systems.
Drain failures — Strainers, collars, and drain bowls deteriorate, causing ponding that accelerates membrane breakdown.
If your existing modified bitumen system has one layer in place and the deck is in sound condition, a recovery (overlay) installation places a new membrane over the existing system. This eliminates the tear-off cost and is significantly less expensive than a full re-roof. It is only appropriate when the existing system meets eligibility criteria, we assess this as part of every replacement evaluation.
We assess every system individually and tell you whether repair, overlay, or full replacement is the right answer.
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