The two systems, priced side by side
The price gap between interior and exterior work is not a quality gap. It is an excavation gap - one system needs a machine and your garden, the other needs a jackhammer and a weekend.
Interior: $55-110 per linear foot
Exterior: $95-250 per linear foot
Interior job: 2-3 days
Exterior job: 5-10 days plus landscaping
On a typical 140 linear foot perimeter anywhere in the United States, that works out to roughly $7,700-15,400 interior against $13,300-35,000 exterior. The wider spread on the exterior number is excavation depth, which nobody can price accurately until they dig.
Across the United States exterior work also carries costs that rarely appear on the quote: 1 or 2 mature shrubs that do not survive, a patio section that has to come up, and a lawn that needs a season to recover. Ask for those to be listed explicitly.
Interior systems are installed in an estimated 8 out of 10 residential waterproofing jobs in the United States, not because they are better but because wall-joint entry is by far the most common pattern.
What is inside each price
- Interior: jackhammering the slab perimeter, laying perforated pipe in stone, new sump basin and pump, patching the concrete
- Exterior: excavation to the footing, cleaning and sealing the wall, membrane or dimple board, footing drain, backfill and compaction
- Both: a discharge line that gets the water far enough from the house, which is the part most often done badly
Common questions
Can I do interior drain tile myself?
The jackhammering is genuinely doable and the pipe laying is not hard. What people get wrong is the slope and the discharge: pipe laid flat holds water instead of moving it, and a discharge line that dumps six feet from the wall recirculates the same water. If you do it yourself, rent a laser level and run the discharge to daylight or a storm connection where the code allows it.
Why do some quotes include a battery backup and others do not?
Because basements flood during storms and storms cause power cuts. A backup pump adds roughly $600-1,200 and it is the difference between a system that works when you need it and one that does not. It is not upselling.