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Basement waterproofing

Basement waterproofing in Maryland

Waterproofing keeps the next storm out. It's a different job from drying out a flooded basement, and the right fix depends on where the water gets in. Start outside, where the cheapest fixes are.

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Local Water & Mold is a referral service. A participating local company answers the call and does the work.

How the work goes

What a professional basement waterproofing job involves

  1. 01

    Find the entry point

    Watch where water appears and when: at the wall-floor joint, through cracks, up through the slab, or down the walls from above grade. Timing after storms points to surface water or groundwater.

  2. 02

    Fix the outside first

    Clean gutters, extend downspouts well away from the foundation, and regrade soil so it slopes away from the house. Many wet basements stop here.

  3. 03

    Relieve water pressure

    Where groundwater pushes in, an interior perimeter drain or exterior drain tile carries it to a sump pump before it reaches the floor.

  4. 04

    Seal and protect

    Inject foundation cracks, apply exterior membranes when excavating, add a battery backup to the sump pump, and dehumidify.

Why Maryland basements leak

In Maryland, the typical county gets 9.3 days a year with an inch or more of rain (NOAA, 2015–2024). Those are the storms that saturate soil around a foundation, push groundwater against basement walls and overwhelm gutters and storm drains. These counties average the most heavy-rain days:

Match the fix to the water

What you seeLikely causeUsual fix
Water near a downspout or one corner during rainRoof runoff and gradingDownspout extensions, gutter repair, regrading
Water at the joint where wall meets floorGroundwater pressureInterior perimeter drain and sump pump
Water through a wall crackCrack in poured concreteCrack injection; exterior repair if it keeps leaking
Water up through floor cracks or a floor drainHigh water table or sewer backupSump system; backwater valve if it's sewage
Damp walls, white crust, musty smell, no puddlesMoisture moving through masonry, or condensationExterior drainage fixes, dehumidifier, sealer as a finish
Walls bowing, stair-step cracks in blockSoil pressure on the foundationStructural evaluation first; waterproofing alone won't fix it

Questions to ask a waterproofing contractor

  • Where exactly is the water coming in, and how did you determine that?
  • What will you do outside (gutters, downspouts, grading) before anything inside?
  • What sump pump, discharge line and battery backup are included, and where will it discharge?
  • What does the warranty cover, is it transferable, and does it cover the result (a dry basement) or only the parts?
  • Do you need a permit, and who pulls it?

Maryland contractor and contract rules

Licensing rules for contractors in Maryland vary by trade and by city or county. Ask for proof of insurance and any license or registration your local building department requires, and check that the company name matches the paperwork and the truck.

The FTC's Cooling-Off Rule generally gives you until midnight of the third business day to cancel a sale of $25 or more made at your home, and the seller must tell you about that right and give you cancellation forms. If you ask for emergency repairs, the right can be waived only with a separate, dated statement in your own handwriting describing the emergency, so don't sign one under pressure. State law may add more protection.

Questions

Basement waterproofing FAQ

What's the difference between basement waterproofing and water damage restoration?
Restoration dries and repairs a basement after water gets in. Waterproofing stops water from getting in next time, with drainage, sump pumps, grading and sealing. If the basement is wet now, dry it first; then fix the cause.
Do waterproof paints and sealers work?
Masonry sealers can reduce dampness from minor moisture moving through concrete or block. They don't hold back water under pressure from saturated soil, and they can peel off when they try. Treat them as a finishing step, not the fix for active leaks.
Interior drain or exterior waterproofing: which is better?
Exterior waterproofing (excavating to apply a membrane and drain tile) stops water before it reaches the wall but is disruptive and expensive. An interior perimeter drain with a sump pump manages water that gets through and is usually less costly. The right choice depends on the soil, the foundation and what's inside the basement.
Does homeowners insurance pay for basement waterproofing?
No. Waterproofing is maintenance and improvement. Insurance may cover sudden water damage, and sump pump or sewer backup damage only with a water backup endorsement, but not the cost of preventing future seepage.
How do I know if water is from the surface or groundwater?
Surface water shows up during or soon after rain, often near downspouts or low corners, and on the upper part of walls. Groundwater shows up at the wall-floor joint or through the slab, often hours or days after storms or in wet seasons, and can persist.

Read next

Basement flooding and sump pumpsWhat to do when it's wet right nowSewer backupsBackwater valves and coverageCrawl space water and moldVapor barriers vs. encapsulation

Local help

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Each county page has local risk data and the call line for that area.

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