What Are Exterior Waterproofing Membranes?
Exterior waterproofing membranes seal the outside face of a basement or foundation wall against the soil, the side where water pressure actually acts. It is the most thorough way to keep moisture out of the wall because it stops water before it can enter the block or concrete, rather than managing it after it is already inside. The approach requires excavating down to the footing to expose the wall, so APS recommends it where wall dampness, efflorescence, or seepage is significant and where access allows. Combined with a proper footing drain, the membrane both blocks moisture and gives any water that reaches the wall a path down and away. In Alabama's moisture-holding clay, protecting the soil side of the wall is a durable, root-cause fix.
How Exterior Waterproofing Membranes Work
The soil is excavated along the foundation to expose the exterior wall down to the footing. The wall is cleaned and prepared, then a waterproofing membrane is applied to seal the surface against water. A dimpled drainage board is often added over the membrane to create an air gap and channel water downward. At the base, a footing drain in gravel collects that water and carries it away. The result is a two-part defense: the membrane blocks moisture from entering the wall, and the drainage board and footing drain relieve pressure by moving water to a safe outlet.
“The outside of the wall is where the water pressure lives. Seal it there and drain it there, and the inside stays dry for the long haul.”
How APS Installs Exterior Waterproofing Membranes
- 1
Assessment and Access Plan
APS confirms exterior waterproofing is the right approach and plans excavation around access, utilities, and landscaping.
- 2
Excavate to the Footing
Soil is carefully removed along the wall down to the footing to fully expose the exterior surface.
- 3
Wall Prep and Membrane Application
The wall is cleaned and repaired as needed, then the waterproofing membrane is applied to seal the soil-side surface.
- 4
Drainage Board and Footing Drain
A dimpled drainage board is placed over the membrane and a footing drain in gravel is installed at the base to carry water away.
- 5
Backfill and Restore
The excavation is backfilled with attention to grading away from the wall, and the surface is restored.
What Exterior Waterproofing Membranes Cost and What Is Covered
Cost Range
Cost depends on the linear footage, access, and system specified. APS provides a free written estimate after the assessment.
Warranty
APS in-house workmanship warranty plus manufacturer warranties on system components, both fully transferable to future owners
Frequently Asked Questions
How is this different from interior drainage?
Interior drainage manages water after it reaches the footing inside; exterior membranes stop water on the outside before it enters the wall. Exterior work is more involved because it requires excavation, but it addresses moisture at the true source. APS recommends the approach that matches your situation.
Do you have to dig up my whole foundation?
Only the affected areas need excavation, not necessarily the entire perimeter. APS targets the walls where moisture is entering, which controls both cost and disruption while still solving the problem.
Will it stop efflorescence and damp walls?
Yes, when the wall dampness is coming from the soil side, sealing the exterior removes the moisture path that produces efflorescence and damp block. APS confirms the source during the assessment so the fix matches the cause.
How long does an exterior membrane last?
Modern membranes are engineered for long service life below grade, and APS backs the work with a transferable warranty. Proper backfill, grading, and drainage at installation are what protect that lifespan.