Method comparison
Five methods, five very different prices
Two contractors can walk the same basement and return quotes $9,000 apart while both are being honest. They are proposing different work. This page names the five things they might be proposing, so you can tell which one you are being sold.
Interior work · average
$3,000
Manages water that has already reached the foundation — collecting it at the wall and floor joint and pumping it away. The floor gets cut; the garden does not.
Exterior work · average
$7,000
Stops water reaching the foundation at all — excavating to the footing and sealing the wall from outside. More disruptive, more expensive, and sometimes the only real fix.
Averages published by Angi, retrieved 2026-08-30.
Sealants & crack repair
$600–$1,500
Waterproof coatings and injected crack sealing applied to the interior wall.
When it fits
Minor seepage or damp patches with no standing water and no hydrostatic pressure.
Watch for
Sold as a permanent fix for a drainage problem. It treats the wall surface, not the water pushing against it.
Interior drainage system
$3,000–$8,000
An interior perimeter drain channel under the slab edge, routed to a sump pump. The floor is cut, not the yard.
When it fits
Recurring water entry at the wall/floor joint. The most commonly quoted real fix.
Watch for
Whether the sump pump, battery backup and discharge line are inside the quoted price or added later.
Interior French drain
$4,000–$17,000
A gravel-bedded perforated pipe run inside the footing line.
When it fits
Higher volumes of water than a basic channel system can carry.
Watch for
The range is enormous. A quote near the top of it should come with a stated linear-foot count.
Exterior excavation & membrane
$8,000–$15,000
Excavating to the footing, then applying membrane and exterior drainage against the outside wall.
When it fits
Structural or persistent water intrusion where the wall itself must be sealed from outside.
Watch for
Landscaping, hardscape and utility reinstatement. Full excavation jobs can pass $20,000.
Exterior French drain
$30–$90 per ft
A drain line installed outside the foundation to move water away before it reaches the wall.
When it fits
Surface and shallow groundwater arriving from a specific direction.
Watch for
Quotes given as a lump sum with no linear-foot figure cannot be compared to anything.
What makes two quotes actually comparable
A quote you can compare states all five of these. One that states none of them is not a cheaper bid — it is an unmeasurable one.
- Which method, named — not just “waterproofing system”.
- Linear feet of drain, or square feet of wall treated.
- Whether the sump pump, battery backup and discharge line are included.
- What happens to landscaping, hardscape and utilities on an exterior dig.
- What the warranty covers, who honours it, and whether it transfers on sale.