Basement Waterproofing in Greenwich, CT
Backcountry ledge estates and Sound-front homes in Byram, Riverside and Old Greenwich sit at opposite ends of the same water problem.

Why Greenwich basements need waterproofing
Greenwich basements fail for two very different reasons depending on where you are. In the backcountry, homes sit on shallow bedrock ledge where rainwater runs along the rock and pushes hydrostatic pressure against foundation walls with nowhere to drain. Down by the water — Byram, Belle Haven, Riverside, Old Greenwich — the water table sits high and close to Long Island Sound, so basements and crawl spaces weep vapor year-round even without a visible leak.
Many Greenwich homes are also old enough to have fieldstone or mortared-rubble foundations that seep through the joints during every heavy rain. We start every Greenwich assessment with thermal imaging and moisture mapping to separate a genuine groundwater problem from an above-grade source (roof, plumbing, grading), then prescribe interior drainage, exterior membrane, Stego vapor barrier, or crack injection based on what the readings actually show.
How we waterproof Greenwich basements
We tailor the system to the source of the water. See the full detail on our basement waterproofing hub.
Interior Drain Tile + Sump
Perimeter French drain to a battery-backup sump — the standard fix when exterior excavation isn't practical.
Stego Vapor Barriers (ASTM E1643)
Below-slab barrier that stops vapor migrating up through soil — the top source of chronic basement humidity.
Foundation Crack Injection
Polyurethane or epoxy full-depth seal for leaking foundation cracks under hydrostatic pressure.
Exterior Excavation + Membrane
Dig out the wall, apply waterproof membrane, drain to daylight — the durable fix for chronic exterior intrusion.
EZ Breathe Ventilation
Whole-basement moisture, mold-spore, radon and VOC removal — the preventive final step after a dry-out.
Grading + Downspout Correction
Often the cheapest, highest-impact fix: slope soil away from the foundation and move roof water off the walls.
Real waterproofing work near Greenwich
Selected photos from waterproofing assessments and projects across Fairfield + Westchester. The pattern is consistent: find the source, install the right system, verify with moisture mapping.




Greenwich basement waterproofing — FAQ
Will homeowners insurance cover basement waterproofing?+
Preventive waterproofing is almost never covered — policies pay for sudden, accidental water events, not moisture prevention. If waterproofing is needed to restore damage from a covered event (a burst pipe, for example), it can be folded into that claim scope. We tell you honestly during the free assessment whether any part is claimable.
How do you decide between interior and exterior waterproofing?+
It depends on the source, which we identify first with thermal imaging and moisture mapping. Hydrostatic pressure from outside the foundation usually calls for exterior grading, drainage or membrane; vapor and seepage through walls or slab is handled with interior systems (drain tile, Stego, EZ Breathe). Often a combined approach is best — but we never prescribe before we've found the actual water source.
How is 911 Storm different from a typical waterproofing contractor?+
We're an IICRC-certified restoration company first, waterproofers second — so we approach basement moisture as a building-science problem and use thermal imaging + moisture mapping to find the real source, not just sell a system. If your problem is actually from above (roof, plumbing), we'll tell you. If it's groundwater, we install the right system with the right manufacturer warranty.
Do you waterproof the older stone foundations common in Greenwich?+
Yes. Fieldstone and mortared-rubble foundations are common in Byram, Cos Cob and the older backcountry estates. They seep through the mortar joints rather than through cracks, so the fix is usually an interior drainage channel + sump combined with parging and a vapor barrier, not crack injection. We assess the wall condition on site before quoting.
Basement waterproofing in nearby towns
Free basement waterproofing assessment in Greenwich
60-minute response, no obligation, no high-pressure sales. We find the water source before we quote a system.
IICRC Certified • Licensed & Insured • All Major Insurance Carriers