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Foundation Wall Water Seepage
in Ann Arbor, MI
Water seeping through foundation walls is one of the most common calls we get in Ann Arbor, especially after the 3 to 4 inches of rain that can fall here in a single April or May storm. The heavy clay soil holds that water against the wall for days after a storm, and any crack, joint, or thin spot in the wall becomes a path inside. Left alone, seepage causes mold, damages stored belongings, and eventually weakens the wall itself.
Quick Answer
Water getting through your foundation wall in Ann Arbor almost always means the waterproofing on the outside of the wall has failed, or there was never much to begin with. Homes built before 1980 often have nothing more than a tar coat on the outside. The fix depends on how bad the seepage is, ranging from interior crack injection to a full exterior waterproofing job. Don't wait. Water damage compounds fast and leads to mold.
Telltale Signs
Warning Signs to Watch For
- Water stains or wet streaks running down the interior wall surface
- Standing water on the basement floor after rain or snowmelt
- A white powdery crust on the wall called efflorescence, which is mineral deposits left by evaporating water
- Mold or mildew smell in the basement even when it looks dry
- Paint bubbling off the interior side of the wall
- Damp insulation or wet framing in a finished basement
Root Causes
What Causes Foundation Wall Water Seepage?
Failed exterior waterproofing
Most Ann Arbor homes built before 1980 have only a thin tar or parging coat on the outside of the foundation. That coating cracks and deteriorates over decades. Once it is gone, the wet clay soil sits directly against bare concrete or block and water moves through.
The Fix
Exterior Waterproofing Excavation
The soil is excavated down to the foundation footing, the wall is cleaned and any cracks are repaired, and a modern waterproofing membrane is applied. A drainage board is placed over it to direct water down and away before it reaches the wall.
Cove joint gap at floor and wall
The cove joint is where the floor slab meets the foundation wall. It is rarely bonded together and is a common entry point for groundwater. When the water table rises after heavy rains in lower-lying neighborhoods like Riverside Park, water pushes in right at that gap.
The Fix
Interior French Drain and Sump Pump
A channel is cut at the base of the wall along the perimeter, a drain pipe collects the water before it spreads across the floor, and a sump pump moves it outside. This does not stop the water from entering the wall but it controls it before it causes damage.
Porous block wall construction
Concrete block walls are hollow and porous. Water soaks through the face of each block and also travels down through the cores inside the blocks. Older homes in Ann Arbor neighborhoods like Kerrytown often have block foundations that were never sealed on the interior or exterior.
The Fix
Masonry Waterproofing Coating
A hydraulic cement is used to plug active leaks first, then a crystalline waterproofing product is applied to the interior face of the block. It grows into the pores of the block and forms a physical barrier against water.
Self-Diagnosis
Which Cause Applies to You?
Check the signs you're observing to narrow down the likely root cause before your inspection.
| What You're Seeing | Failed exterior waterproofing | Cove joint gap at floor and wall | Porous block wall construction |
|---|---|---|---|
| Water comes in at the base of the wall near the floor | |||
| Seepage appears across a wide area of the block face | |||
| Water stains appear higher on the wall after heavy rain | |||
| Seepage is worst on one wall that faces a slope or downhill grade | |||
| Water appears right after rain but dries within a day | |||
| Water appears days after rain, not immediately |
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