How to choose a basement waterproofing company in Long Island

1. Start with the job you need

Interior drainage, exterior membrane and foundation repair are different jobs. Some companies here are waterproofing specialists, some are foundation-repair firms that also waterproof, and some offer waterproofing as one line among others, such as general remodeling or masonry. Start with companies that state your kind of job in their own words.

2. Ask whether an interior system, an exterior system, or both fit your basement

An interior system collects water inside and channels it to a sump pump. An exterior system excavates outside and seals the wall with a membrane. Ask the company which option fits your foundation, your soil and your property, and what each one includes.

3. Get the scope in writing

Ask what is included: drainage, sump pump and backup power, crack repair, discharge lines, permits, documentation and restoration. A quote that does not list those parts is not comparable with one that does.

4. Ask how the price is calculated

Ask whether the price is by job, by linear foot, or a flat scope price, and what would change it. No company in this guide publishes a fixed waterproofing price, so every figure you are given is a range or a discount until it is written as a firm quote for your exact basement.

5. Verify the license yourself

Ask the company for its license number and verify it yourself with the county: only 4 of the 20 companies in this guide publish a license number on their own website. A claim on a website is not a verified credential, a directory award is not a license, and a mold-remediation license is not a waterproofing license.

6. Ask about permits and discharge

Ask which county requirements apply to your job, who obtains them, where the discharge water goes, and whether backup power is included.

7. Ask about the warranty

Ask what the warranty covers, for how long, whether it transfers to a new owner, and what maintenance the system needs.

8. Service-area companies

A service-area company serves Long Island but publishes no street address on its own site. That is not a red flag on its own, but confirm response time, who comes to your home, and whether the crew is in-house or subcontracted before you book.

9. Get it in writing before work starts

Scope, system type, permits, discharge, crew, timeline, warranty and total price should all be in one written quote. Verbal promises about price, timeline or results are hard to enforce later.