Last updated: September 22, 2026
Basement waterproofing in Maryland runs from about $500 for minor crack sealing to $4,000+ for sump-pump and drainage systems — most Montgomery County jobs land between $1,200 and $4,000. Waterproof first, finish second. Here’s what each fix costs.
These are planning ranges, not quotes. Every project is different. What you actually pay depends on the size of the space, the condition of what is behind the walls, your material selections, and whether plumbing, electrical, or framing has to move — none of which can be judged from a photo or a phone call. Think2Remodel provides a firm written price only after an on-site consultation where we measure and inspect the space in person. Book a free on-site consultation.
How Much Does It Cost to Waterproof a Basement?
Cost depends entirely on the source of the water and the method needed. Typical Montgomery County ranges:
| Method | What it fixes | Typical cost |
|---|---|---|
| Interior sealant / waterproof paint | Minor dampness, humidity | $500 – $1,500 |
| Crack injection | Isolated foundation cracks | $500 – $1,800 per crack |
| Sump pump install | Water pooling / rising water table | $1,200 – $3,000 |
| Interior drainage + sump system | Recurring seepage at the floor/wall joint | $4,000 – $9,000 |
| Exterior excavation + membrane | Serious hydrostatic pressure, wall leaks | $9,000 – $18,000+ |
What Drives the Cost
Four things move the number: the size of the basement, the source and severity of the water, whether the fix is interior or exterior (exterior is far more invasive), and whether the space is already finished (removing and replacing drywall adds cost). Most Montgomery County homes with recurring seepage land in the interior-drainage range of $4,000–$9,000.
Should You Waterproof Before Finishing a Basement?
Yes. Finishing over an unaddressed moisture problem risks ruined drywall, flooring, and mold within a year or two. Waterproof first, then finish. If you’re adding a bedroom, you’ll also need a compliant egress window. See our basement finishing services and the basement finishing cost guide for the full picture.
Frequently Asked Questions
How much does it cost to waterproof a basement in Maryland?
Most Montgomery County basements cost $500-$1,500 for minor sealing, or $4,000-$9,000 for an interior drainage and sump system. Serious exterior waterproofing can run $9,000-$18,000 or more.
Is basement waterproofing worth it before finishing?
Yes. Finishing over a moisture problem usually leads to ruined drywall and mold within a year or two. Waterproofing first protects the entire investment.
How long does basement waterproofing take?
Interior drainage systems typically take 2-4 days. Simple crack injection or sealing can be done in a day.
Related: Planning a basement? See basement finishing cost in Maryland.
Related reading: Planning to finish it afterwards? See our guide to basement finishing costs in Montgomery County.