Six fixes get sold under the word "waterproofing," and they range from a $50 downspout extension to a five-figure excavation. Most metro Detroit basements need the cheap end of that list, in a specific order. Here is what each one does and where it sits.
The cheap fixes that prevent the most problems
Gutters and downspout extensions
The single cheapest protection there is. Clogged gutters and downspouts that dump water right at the foundation are a leading cause of basement moisture. Extending downspouts at least six feet from the house moves thousands of gallons a year away from your walls, the kind of low-cost measure federal flood guidance puts first (FEMA, Protect Your Property From Flooding). Cost: $0 to $200, mostly do-it-yourself.
Grading
The soil around your foundation should slope away from the house, not toward it. Regrading or building up low spots is the second-cheapest thing on this list and the second most effective. Cost: $0 to $200 for a load of soil and a weekend, more if a landscaper does it. Oakland County homeowners can offset some of this through RainSmart rebates for downspout disconnection and rain gardens.
The mechanical systems
Sump pump (and a battery backup)
A sump pump sits in a pit at the low point of your basement and pumps incoming water out before it floods the floor. It is essential equipment for most metro Detroit homes. The most common failure point is a power outage during the exact storm you need it, which is why a battery backup is one of the highest-value upgrades you can make. Cost: $1,500 to $3,500 for a backup pump, per our 2026 sump pump pricing.
Backwater valve
A backwater valve installs on your main sewer line and closes automatically if the municipal sewer backs up, stopping sewage from pushing into your basement. For older homes on combined sewers, this is the fix that addresses the 2021-style disaster. Cost: $1,500 to $3,500 as a standalone retrofit, the planning range we use across this site.
The bigger drainage systems
Interior weeping tile (drain tile)
A perforated pipe installed inside the perimeter of the basement floor collects water that reaches the footing and routes it to the sump. This is the workhorse of interior waterproofing for chronic seepage. Cost: $4,000 to $12,000 installed, roughly $40 to $85 per linear foot.
Exterior waterproofing and excavation
Digging out around the foundation to seal the walls and install exterior drainage. It is the last resort, for a basement that keeps taking water after an interior system is already in. Cost: $10,000 to $25,000 and up.
Match the fix to your actual risk
Which system you need comes down to three things: when your house was built, whether it sits on the clay that covers most of Wayne, Oakland, and Macomb, and whether your street runs on a combined sewer. Once the water is controlled, keep the finished space itself dry: the EPA recommends holding indoor humidity below 60 percent to stop mold before it starts (EPA). Start by checking your neighborhood's Basement Risk Index, then have a qualified professional confirm what your home needs.
Sources reviewed
Primary sources checked September 2026:
- EPA, A Brief Guide to Mold, Moisture and Your Home, drying wet materials within 24 to 48 hours and holding indoor humidity below 60 percent.
- FEMA, Protect Your Property From Flooding, the low-cost grading, gutter, and downspout measures that keep water off the foundation.
- Oakland County Water Resources Commissioner, RainSmart rebates, rebates for downspout disconnection and rain gardens.