Basement Waterproofing Options Explained

By Ishaq Hassan. Updated October 10, 2026. 3 min read.

Short answer: Basement waterproofing starts outside, with gutters, downspouts and grading that keep water away. Inside, the main options are sealing cracks, installing an interior drain tile and sump pump, and dehumidifying. Exterior waterproofing, which excavates and seals the outside of the walls, is the most thorough but also the most disruptive.

A wet basement ruins stored belongings, grows mold and can signal foundation problems. The right fix depends on where the water comes from. This guide explains basement waterproofing options, from simple to major.

First, find where the water comes from

Condensation: damp walls in humid summer, often fixed with a dehumidifier.
Surface water: rain and snowmelt running toward the house, fixed with drainage and grading.
Cracks and joints: water seeping through wall cracks or where the wall meets the floor.
Groundwater: water pushed up by a high water table, called hydrostatic pressure.

A simple test for condensation: tape a square of foil to the wall for a few days. Moisture on the room side points to condensation. Moisture behind it points to water coming through the wall.

Illustration of a concrete block wall with a long crack and water seeping through — Wide or growing cracks, or cracks that let water in, need a closer look.

Outside fixes: start here

Clean and repair gutters
Extend downspouts 4 to 6 feet from the house
Regrade soil to slope away from the foundation
Fix window wells with covers and drains

These are often the lowest cost and most effective steps. Read our guide to downspout drainage.

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Inside waterproofing options

Crack injection: epoxy or polyurethane sealing of individual wall cracks.
Interior drain tile: a perforated pipe in a trench along the inside of the walls that collects water and carries it to a sump pump.
Sump pump: pumps collected water out and away. A battery backup keeps it running in power outages.
Wall coatings and membranes: help with dampness but will not stop water under pressure on their own.
Dehumidifier: controls humidity and condensation.

Illustration of a brick wall with a stair step crack running through the mortar joints below a window — A stair step crack in brick or block often means the foundation below has moved.

Sump pump tips

Test the pump every few months by pouring water into the pit
Install a battery backup or a water powered backup for power outages
Make sure the discharge line carries water well away from the house
Add a high water alarm
Replace older pumps before they fail, often every 7 to 10 years

Exterior waterproofing

Exterior waterproofing digs down to the footing around the outside of the house, cleans and seals the walls with a membrane, and installs footing drains. It stops water before it reaches the wall, but it is disruptive, costly and affected by landscaping, decks and walkways. It is often chosen for new construction or major repairs.

Illustration of a flooded basement with water covering the stairs and boxes floating — Basement flooding often follows heavy rain or a failed sump pump.

When waterproofing becomes foundation repair

Horizontal cracks, bowing walls and stair step cracks can mean soil pressure is moving the walls. Waterproofing alone will not fix this. Have a foundation specialist or structural engineer look first. Read about foundation repair and foundation crack repair.

Illustration of a brick house with a stair step crack running down from a window — Stair step cracks in brick can be a sign of foundation movement.

Quick answers: basement waterproofing

What is the best way to waterproof a basement?

Start with gutters, downspouts and grading. Inside, interior drain tile with a sump pump is a common, effective fix for leaks.

Does waterproof paint work on basement walls?

It can reduce dampness but will not stop water under pressure or through cracks.

Do I need a sump pump?

If groundwater collects under or around the basement, a sump pump with a battery backup is often the key part of the fix.

Is a wet basement a foundation problem?

Not always, but bowing walls, horizontal cracks and stair step cracks need a foundation specialist.

Who waterproofs basements?

A basement waterproofing or foundation company. Sifixit can connect you with local providers.

This guide covered basement waterproofing. For more background, see the FTC’s advice on hiring a contractor and avoiding home improvement scams, and if you need help, Sifixit can connect you with a local provider.

This guide is general information for homeowners, not professional, insurance or safety advice for your situation.

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