Waterproofing guides

Diagnosing. Tape plastic sheeting tightly to a suspect wall for two days. Condensation collects on the room-facing side; seepage collects behind it. Meanwhile, keep a written log of dates, rainfall and where water shows up. EPA advises keeping indoor humidity below 60 percent, ideally 30-50 percent — a $15 hygrometer will tell you whether you have a humidity problem at all.

Outside first. Clean gutters, extend downspouts well clear of the foundation, and check that the ground falls away from the wall. The code reference point is at least 6 inches of fall within the first 10 feet, with swales or drains required where lot lines or walls make that impossible (2021 IRC R401.3). Impervious surfaces within 10 feet should slope at least 2 percent away.

Reading a quote. A quote you can actually compare names: linear feet of drain, pipe type and diameter, filter fabric and stone, pump make and model with horsepower, whether a battery backup is included, discharge line length and destination, what is excavated and what is restored, permit responsibility, and the warranty terms in full. If it is one line and a price, send it back.

Vetting. Ask for license and insurance certificates and verify them with the issuing body yourself, not from a copy the contractor hands you. Licensing requirements for this trade vary by state and city, so check with your state contractor licensing board and your local building department for what is required where you live. Ask for three addresses of jobs done three or more years ago in your area, and actually call them — a waterproofing system that worked for one winter proves nothing.

How to choose

Get the diagnosis in writing

Ask the contractor to write down what they believe the water source is and why. It anchors the warranty conversation if the fix does not work.

Three quotes, at least two methods

If all three quotes are for interior drainage, you have three opinions from the same school. Get one excavation contractor in the mix.

Never pay in full up front

Structure payments against milestones. A materials deposit is normal; most of the money before work starts is not.

Ask about the discharge

Where the pumped water ends up decides whether the problem moves or is solved. Some municipalities also regulate where you may discharge — ask your building department.

Keep every document

Contract, warranty, permit, product data sheets, photos, and the final invoice. You will need them for a warranty claim or for a buyer years from now.