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Foundation & basement waterproofing: the basics
Cracks, bowing walls, settling, piers, sump systems, French drains, crawl spaces.
The full guide for this trade is being written. Until then, here is what we know for sure: the problems that belong here, who handles them, and how to check a contractor.
On this page4 sections: urgent, permits…
What people call about
- Crack in the foundation
- Basement wall bowing
- Water seeps in when it rains
- Crawl space encapsulation
How soon to call
Call in the next day or two
Water seeps into the basement when it rains
Ask for: basement waterproofing (interior drain, exterior grading, crack sealing)
Crack in the basement wall
Ask for: foundation crack evaluation and repair
Hairline vertical cracks are common; horizontal or stair-step cracks, or any crack that is widening, should be seen by a foundation contractor or structural engineer.
Basement wall bowing in
Ask for: wall stabilization (anchors, braces, piers) with an engineer's design
If the wall moved suddenly or is cracking as you watch, keep people out of that area and call today.
Crawl space is wet
Ask for: crawl space drainage and moisture control
Basement window well fills with water
Ask for: window well drainage and cover
Crack in the foundation outside
Ask for: foundation crack evaluation
Need an engineer to look at a crack
Ask for: structural engineer evaluation (ask for a licensed PE)
Crack across the ceiling getting bigger
Ask for: structural evaluation
Schedule it
Basement smells musty
Ask for: moisture assessment and control
White powder on the basement walls
Ask for: moisture assessment
The white powder is mineral left by water moving through the wall; it is a sign, not the problem.
Crawl space encapsulation
Ask for: crawl space encapsulation
General guidance, not a diagnosis. If anyone is in danger, call 911 first.
Permits and licensing
- Some of this work needs a permit, depending on the job and the town. Ask before the work starts.
- Licensing depends on the state: a trade license in some, a home-improvement registration in others, none in the rest. The finder shows what the record says where one exists.
Know what you're looking at
On new foundations the waterproofing goes on before backfill. Seeing it done right is one reason to look at the job while it is open.
National Institute of Standards and Technology · Public domain
Thin hairline cracks are common and often only need sealing. Wide, stair-step or growing cracks, or doors that stick, are reasons to call a structural engineer first.
General information, not legal, tax, engineering or insurance advice. Rules and prices vary by place, so get three local quotes. Problem list updated 2026-10-04.