Ask three waterproofing companies how to fix a wet basement and you can get three different answers. One says dig outside. One says drain tile inside. One says seal the crack. All three can be right. “The water tells you where it’s coming from,” says Imad “Matt” Mansour, owner of Mansour’s Innovations. “Our job is to read it before we sell anybody a system.”
Why Southeast Michigan basements get wet
Much of Southeast Michigan sits on poorly drained lakeplain with heavy clay soil. Clay holds water and lets it go slowly, so after a heavy rain or the spring thaw, water sits against the foundation and pushes through cracks, tie rod holes, the cove joint where the wall meets the floor, or the floor itself.
Match the fix to where the water comes in
One crack or tie rod hole leaking: seal it from inside
If water is coming through a single vertical crack or a tie rod hole, epoxy crack injection seals it through the full wall from inside the basement. No digging, usually done in a day.
Water along the bottom of the wall or floor edge: interior drain tile
Dampness or water at the cove joint means pressure under and around the footing. Interior waterproofing breaks out the floor along the walls, lays drain tile in gravel sloped to a sump pit, and puts dimple board on the walls. Typically two to four days of work. Interior waterproofing runs approximately $6,000 to $8,000 for a 40-foot wall, depending on how many feet of wall. See a real 250-foot interior job in Washington Township.
Leaks in many places, a high water table or a finished basement: exterior waterproofing
When water comes in all over, or the basement is finished and you don’t want walls torn out, exterior waterproofing stops it at the source: excavate to the footing, clean and seal the wall, add a membrane and new drain tile, then backfill. Typically five to ten days. Exterior waterproofing runs approximately $8,000 to $12,000 for a 30-foot wall. Example: exterior waterproofing in Davisburg with no basement demo.
Horizontal cracks or a wall bowing in: structural first
That’s soil pressure, not just a leak. It needs a structural assessment before any waterproofing. See bowing wall repair.
Water rising through the floor drain in storms: that’s the sewer
Water coming up through a floor drain during heavy rain is usually a sewer backup, not groundwater. The fix is a backwater valve, not waterproofing.
Interior vs. exterior basement waterproofing at a glance
- Interior: manages water that gets in, from inside, no yard digging, works year-round, typically 2 to 4 days, approximately $6,000 to $8,000 for a 40-foot wall.
- Exterior: keeps water off the wall entirely, needs excavation, the right fit for finished basements and widespread leaks, typically 5 to 10 days, approximately $8,000 to $12,000 for a 30-foot wall.
- Warranty: drain tile and membrane work from Mansour’s Innovations carries a 25-year transferable limited warranty. The sump pit and pump carry the manufacturer’s warranty.
Before you call anyone, check these
- Downspouts discharge at least 6 feet from the foundation.
- Soil slopes away from the house.
- Window wells are clear.
- Note exactly where the water shows up and after what kind of weather. That tells you, and us, most of what we need to know.
Not sure which one you need? Try our basement problem finder or get a free estimate; we’ll tell you what the water is telling us.
Frequently asked questions
Is interior or exterior basement waterproofing better?
Neither is better for every home. Interior drain tile is right when water comes in along the bottom of the walls; exterior waterproofing is right for leaks in many places, a high water table or a finished basement. A single leaking crack often only needs epoxy injection.
How much does interior vs. exterior waterproofing cost in Michigan?
Interior waterproofing runs approximately $6,000 to $8,000 for a 40-foot wall and exterior waterproofing approximately $8,000 to $12,000 for a 30-foot wall, depending on the length of wall and access.
How long does basement waterproofing take?
Interior drain tile typically takes two to four days. Exterior waterproofing, which needs excavation, typically takes five to ten days.
Why does water come up through my basement floor drain?
Water rising through a floor drain during storms is usually a sewer backup. A backwater valve stops it; waterproofing does not.
Sources: Mansour’s Innovations field experience across Macomb, Oakland and Wayne counties, and USDA soil survey descriptions of Southeast Michigan lakeplain clay soils. This guide expands on our press release, Inside or Outside? How Metro Detroit Homeowners Can Tell Which Basement Waterproofing Fix Fits Their Leak, distributed by EIN Presswire on November 8, 2026.
Mansour’s Innovations is a family-owned waterproofing, excavation and plumbing contractor in Shelby Township, Michigan, serving Macomb, Oakland and Wayne counties since 2014. Owner Imad “Matt” Mansour has 20+ years in the trade and the crew has completed 1,600+ projects. Our waterproofing work carries a 25-year transferable limited warranty. We’re open 8 AM to 8 PM, 7 days a week. Call or text (586) 345-7292 or book a free estimate online.
