What is an exterior membrane?

An exterior membrane is a liquid or sheet-based waterproofing layer installed on the outer surface of a foundation wall that sits below ground level. Common types include elastomeric coatings, bentonite panels, and rubberized membranes, which are applied during or after excavation to create a continuous moisture barrier against groundwater and soil moisture.

This approach differs from dampproofing, which is a lighter-duty moisture control method typically applied with single-coat paint or spray systems. Exterior membranes are thicker, more durable, and designed to handle sustained water pressure and wet soil conditions common in below-grade applications. They are the standard solution for basements and crawl spaces where active water intrusion is a concern.

In Trumbull County, where seasonal water tables and clay soil can drive moisture problems, exterior membranes protect foundations from water damage, mold growth, and structural deterioration. They are installed on the excavated face of the foundation wall before backfill and soil is replaced. The membrane must be continuous and properly sealed at joints, penetrations, and wall transitions to remain effective.

Choosing between an exterior membrane and dampproofing depends on site conditions and moisture risk. Exterior waterproofing contractors can assess your foundation and recommend the appropriate protection level for your property.