Exterior Waterproofing
Membranes
in Maryland

Damp-proofing — typically an asphalt emulsion brushed or sprayed on a foundation — is what most new Maryland homes received from the original builder. It slows moisture vapor transmission through the wall. It is not designed to resist hydrostatic water pressure and will crack, shrink, and deteriorate over time as the foundation moves and the material ages.

A true waterproofing membrane — rubberized asphalt sheet or spray-applied polymer — is a continuous, elastic layer that maintains adhesion and integrity under hydrostatic pressure. It bridges minor foundation movement and remains effective through Maryland's freeze-thaw cycles. If your foundation has only original builder damp-proofing and you're experiencing water intrusion, adding more damp-proofing is not the solution. You need a membrane that can handle pressure, not just vapor.

Primarily rubberized asphalt sheet membrane for wall applications — it bonds directly to concrete and block, remains flexible at Maryland temperature extremes, and carries a documented performance history in the wet clay soil conditions common across Baltimore, Harford, and Carroll Counties. The sheet format allows us to confirm full coverage in a way that spray application sometimes cannot.

Spray-applied polymer membranes are used where sheet membrane cannot fully conform to the surface geometry — irregular block courses, areas with significant patched repair, or penetrations with complex profiles. Both types are covered with drainage board (dimple mat) before backfill to protect the membrane from puncture during soil compaction and to channel groundwater down to footer drainage rather than pooling behind the membrane.

In theory yes — targeted excavation to the failure point, membrane repair or patch application, and re-backfill. This is appropriate when a specific mechanical puncture or installation defect is identified in an otherwise sound membrane that has relatively few service years.

In practice, by the time a membrane fails and the failure becomes detectable inside the basement, the membrane is usually aged enough that targeted repair offers limited additional longevity. If the membrane is 20-plus years old and showing one failure point, it likely has others. OBW will scope this honestly: we'll tell you whether targeted repair or full re-application to the affected section is the better value given membrane age and condition. We don't do targeted repairs to justify a smaller invoice when the honest answer is broader work.

They address different parts of the moisture problem. The membrane stops water from reaching the wall face; interior drainage manages water that gets past the wall — whether through cove joint seepage, existing cracks, or tie rod holes. On a properly waterproofed new construction where the membrane is applied during the build, interior drainage typically isn't needed.

On an older Maryland home where the membrane is being added retroactively, interior drainage is often installed in combination — because you can't guarantee every water entry point is addressed by the membrane alone, particularly when cove joint seepage has been the primary source. In those cases OBW scopes both elements and presents the combined system as the complete solution.

The membrane application itself — once excavation is complete and the surface is cleaned and repaired — is typically one to two days for a standard residential section. A single wall of a Baltimore County split-level might be done in a day; a full-perimeter treatment on a larger colonial in Harford County runs into the second day.

Excavation and backfill are separate phases with their own timeline depending on soil conditions, equipment access to the foundation wall, the length of wall being treated, and any hardscaping or landscaping that needs to come out. OBW provides the full project timeline at quote — not a membrane-only estimate that leaves excavation as a surprise line item.