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Best basement waterproofing pros near Cos Cob, CT

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  • Average homeowner rating star icon4.7
    Average homeowner rating
  • Verified reviews icon46
    Verified basement waterproofing services reviews

Top-Rated Basement waterproofing pros in Cos Cob - Updated Nov 2026

Avatar for Connecticut Basement Systems, Inc.
Connecticut Basement Systems, Inc.
4.3(
589
)
Foundation, Basement or Crawlspace - Waterproofing / EncapsulationBasement Drainage Channels - InstallBasement Drainage Channels - Repair

Serving Cos Cob, CT and surrounding areas

Approved

In business since 1987

Free estimates

Warranties offered

"Great results from waterproofing. Turned my spring flooding anxiety to calm. As humidity rose in summer, I put in a small dehumidifier. Made basement noisy as it struggled to dry and produced a lot of heat. As temperatures rose to about 83 down there and the humidity rose to over 68%, I had same people put in a whole basement commercial-grade dehumidifier. The small unit dropped the humidity to around 50% in less than an hour. Incredible performance and have me peace of mind and peace and quiet downstairs. Temperature dropped gas as well. Weel worth the price to save my most expensive investment."
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+12

176 neighbors recently requested a quote
Recommended by90%of homeowners
Avatar for American Dry Basement Systems, LLC
American Dry Basement Systems, LLC
4.9(
118
)
Foundation, Basement or Crawlspace - Waterproofing / Encapsulation

Serving Cos Cob, CT and surrounding areas

Approved

In business since 1997

Free estimates

Credit card accepted

"I had my basement waterproofed almost 3 years ago by them and I had no issues since then with the basement flooding regardless of how much it rains. I highly recommend using American Dry Basement!"
Drainage Trench
Jackhammer
Mixing SuperCrete
Compress Wash Stones
Spreading SuperCrete

+7

Response time11 hrs
3 neighbors recently requested a quote
Recommended by66%of homeowners
Avatar for Dirty Deeds Basement Waterproofing
Dirty Deeds Basement Waterproofing
5.0(
4
)
Foundation, Basement or Crawlspace - Waterproofing / EncapsulationBasement Drainage Channels - InstallBasement Drainage Channels - Repair

Serving Cos Cob, CT and surrounding areas

Approved

In business since 2012

Free estimates

Emergency services offered

"Dean and his crew were professional, reliable, extremely neat/clean and went above and beyond, often, to make the sure work was completed to my satisfaction. They did small things not even required to make sure the entire basement area was much more than even expected. The basement has never been so dry in the 40 years I have lived here. I would hire them again in a heartbeat."
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+24

Response time7 hrs
6 neighbors recently requested a quote
Recommended by100%of homeowners
Avatar for Groundworks
Groundworks
4.9(
13
)
Foundation, Basement or Crawlspace - Waterproofing / EncapsulationBasement Drainage Channels - InstallBasement Drainage Channels - Repair

Serving Cos Cob, CT and surrounding areas

Approved (Corporate)

Super Service Award Winner

In business since 2025

Free estimates

Warranties offered

Groundworks is the North America's leading and fastest-growing foundation repair and water management solutions provider. Groundworks is a vertically integrated company with its own manufacturing operations and a world-class software solution, allowing us to serve our customers more effectively. From the first phone call to the annual maintenance offered, our customers have peace of mind knowing we're there with one mission to repair, protect and improve their home. For state licenses visit Groundworks.com/licensing

Foundation
Foundation
Foundation
Concrete
Concrete

+16

504 neighbors recently requested a quote
Avatar for AG Property Maintenance, LLC
AG Property Maintenance, LLC
4.6(
12
)
Foundation, Basement or Crawlspace - Waterproofing / Encapsulation

Serving Cos Cob, CT and surrounding areas

Approved

In business since 2012

Free estimates

Offers commercial services

"Pedro and team solved an ongoing pond drainage issue that was able to be resolved. Many companies came and charged us money for half a job and this was not the case with AG. They were professional, proficient and quickly got to the source of the problem in one day. Prices were fair and they did not have to come back as they had all the supplies they needed to start and finish the job which is very rare for a major culvert issue like this one."
Brookfield ct
Brookfield ct
Brookfield ct
Brookfield ct
Brookfield ct

+4

Response time2 days
3 neighbors recently requested a quote
Recommended by100%of homeowners
Avatar for KNL CONSTRUCTOR LLC
KNL CONSTRUCTOR LLC
5.0(
11
)
Basement Drainage Channels - Install

Serving Cos Cob, CT and surrounding areas

Approved

In business since 2020

Free estimates

Credit card accepted

*****Call Today for an Estimate @ 475-279-4864***** With over 10 years of experience, I take pride in my quality craftsmanship. We are owner operated, and believe in building long-term relationships with our clients by delivering honesty along with exceptional work. We pride our company on reliability, great communication, integrity, and customer service. We are experts in our trade and will do our best to keep you as educated as we can on your particular project. Give us a call today! We look forward to working with you!

Pavers
Pavers
Concrete Border
Concrete Border
Bluestone

+2

23 neighbors recently requested a quote
Recommended by66%of homeowners
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Basement Waterproofing FAQs, answered by experts

You should take care of any sign of water in your basement, whether it’s dampness after heavy rain or puddles of water on the floor. Besides potentially causing a health hazard, the moisture can damage your home’s structure and foundation. Furthermore, mold can grow quickly and spread throughout the rest of your home. With mold remediation costs ranging between $1,200 and $3,400, it’s best to avoid mold issues by fixing the leak.

Water can seep into porous materials like wood beams, floor joists, and roof rafters within minutes, but they’ll need to see prolonged exposure before you have structural damage. Mold can start growing within 24 hours, and mold can eat away at the structural components over time. Wood rot is more of a concern, though. Wet and dry rot are fungal infections that set in in moist conditions and rapidly deteriorate wood, causing major structural damage within just a few months in some cases.

As the first layer of water protection for your roof deck and the building materials below, underlayment is designed to prevent water damage, so it’s okay if it gets wet. However, you shouldn’t rely solely on underlayment for protection. If rain interrupts your roof project and you have all of the underlayment down, you’ll likely be fine, but you should install shingles over that layer as soon as possible, as long-term exposure can lead to water damage.

To ensure your basement walls are waterproof, it's crucial to address any existing moisture issues before finishing. Inspect for signs of water seepage, such as dampness or discoloration, and repair any leaks or cracks. Install a vapor barrier to prevent moisture from penetrating the walls, and consider waterproofing paints or coatings.

Proper drainage systems, such as interior or exterior waterproofing, can also be beneficial.

Waterproofing or encapsulating protects against moisture, preventing mold growth and structural damage. These services also enhance energy efficiency and improve air quality by keeping humidity levels in check.

The Cos Cob, CT homeowners’ guide to basement waterproofing services

From average costs to expert advice, get all the answers you need to get your job done.