Can you waterproof an existing basement?

Author: Prof. Hailey Barton  |  Last update: Monday, December 15, 2025

There are two general methods for waterproofing existing basements: By using Type C Cavity Drainage Membranes or by using Internal type A Barrier Systems. Type C Cavity Drainage Systems are generally considered to be the most reliable form of waterproofing and require less surface preparation in order to be successful.

Can you waterproof an already finished basement?

An exterior waterproofing membrane can also be used when water enters the finished basement through porous concrete or over the top of a foundation wall.

How much does it cost to waterproof an existing basement?

Basement waterproofing costs $5,213 on average, and most homeowners pay somewhere between $2,459 and $8,181 depending on the waterproofing method, the extent of the issue, and the size of the home.

Can I waterproof my basement from the inside?

Yes, you can seal a basement from the inside using several methods. Here are some common approaches: Waterproofing Paints and Sealants: These products can be applied directly to the walls and floors of the basement to create a waterproof barrier. Look for specifically formulated waterproofing paints or sealants.

Is it worth it to waterproof a basement?

According to some water damage studies, over 98% of all homes with basements will experience some kind of water damage. Even a minor leak will raise your water bill by 10%. A properly waterproofed basement can be a great selling point for potential buyers and typically offers a return on investment of about 30%.

Basement Waterproofing - How To Permanently Waterproof A Basement

What are the disadvantages of basement waterproofing?

Exterior basement waterproofing has a few downsides, though.
  • Cost. It's a more involved process that requires digging up your yard, which is expensive and time-consuming.
  • Damages landscaping or hardscaping elements. ...
  • Not serviceable.

How do you permanently waterproof a basement?

5 Steps to Effectively Waterproof Basement Walls
  1. Remove All Standing Water and Verify That the Area is Completely Dry. ...
  2. Clean and Prepare the Area. ...
  3. Plug Holes and Cracks. ...
  4. Reseal Windows, Doors and Window Wells with Caulk. ...
  5. Apply Waterproof Coating.

How long does interior basement waterproofing last?

Generally, waterproofing lasts 5-10 years but can extend to decades with proper maintenance. To ensure longevity: Regularly inspect and maintain the system. Discuss specific longevity expectations with your contractor.

What is negative waterproofing?

What is negative side waterproofing. Negative side applied waterproofing is applied to the internal surfaces of the structure, usually when there is no access or ability to either get access to the access to the external surfaces or where continuity is not possible.

Can I use flex seal in my basement?

Apply Flex Seal Products

Flex Shot and Flex Seal Liquid are great options for attacking a basement wall leak.

Does homeowners insurance cover basement waterproofing?

Although basement waterproofing isn't directly covered by insurance, it is possible to add an endorsement to your homeowner's insurance policy covering your things like a broken sump pump, burst pipes, or extreme weather events like a lightning strike.

What is the cheapest way to waterproof basement walls?

The cheapest basement waterproofing method is typically applying a waterproof paint coating, which can cost as little as a few dollars per square foot for materials if doing it yourself.

Do you need a license to waterproof basements?

The first thing you should ask any basement waterproofing service is whether they have a valid license. Most states require waterproofing companies to have a valid license or permit to carry out their operations. Steer clear of any waterproofing company without proper licensing.

What is the best DIY basement waterproofing?

What can I use to waterproof my basement? For minor leaks and moisture, you can use hydraulic cement, silicate concrete sealant, and silicone caulk to fill cracks and gaps. You can apply these products yourself, followed by waterproof paint.

Does waterproofing a basement increase home value?

Waterproofing your basement can increase/ recover the resale value of your home by up to 10-20%. This is because it makes your property more attractive to potential buyers and reduces the likelihood of future repair costs.

What are the three types of basement waterproofing?

The 3 Major Approaches to Basement Waterproofing
  • Sealants & Epoxy Injections. Sealants and epoxy injections are widely considered band-aid fixes, but some homeowners opt for these sealants as the next-best solution when a drainage system isn't in their budget. ...
  • Interior Drainage. ...
  • Exterior Waterproofing.

What is the strongest waterproofing?

POLYURETHANE

Polyurethane is considered one of the best waterproofing materials. It can be applied seamlessly and penetrates the surface deeply and evenly. Thus, the polyurethane membrane will fill in even the finest cracks in concrete, reducing its water absorbency capacity.

What are the disadvantages of waterproofing?

Cons Of Waterproofing
  • High Initial Costs. The upfront waterproofing costs can be substantial, especially if external methods are used. ...
  • Regular Maintenance May Be Required. ...
  • Temperature Sensitivity. ...
  • Potential For Incorrect Installation. ...
  • Reduced Breathability.

What is class 2 waterproofing?

• Classification of waterproof membranes. • Class I membranes: Resin (fiberglass) systems, Water based Epoxies. • Class II membranes: Acrylic. membranes, Bitumen based.

How much is the average cost to waterproof a basement?

Basement waterproofing costs homeowners an average of $3,000–$10,000 for a 1,000 square foot basement. See which factors will impact your total cost.

Can you waterproof an old basement?

Applying Waterproof Masonry Cement

After sealing cracks, you can apply a coat of waterproof masonry cement to your basement walls for additional protection. We recommend applying at least two coats to seal the pores of the concrete and prevent moisture from seeping through the walls.

How do professionals waterproof basements?

The most common basement waterproofing methods include:
  • Exterior waterproofing coating.
  • Interior sealants.
  • Interior water drainage.
  • French drains (interior and exterior)
  • Sump pump installation.

Can you waterproof a basement only from the inside?

Waterproofing Basement Walls From Inside Only Is Usually Not Enough. When researching the internet, most results show that waterproofing basement walls from inside only is usually not enough to keep moisture out of your basement.

How do I stop water from seeping in my basement?

The following practical tips can help you effectively avoid extensive foundation leak repair and keep water out of your basement after heavy rain.
  1. Add a Sump Pump. ...
  2. Install a Dehumidifier. ...
  3. Maintain Gutters and Downspouts. ...
  4. Ensure Proper Landscape Grading. ...
  5. Add or Replace Exterior Drainage and Damp Proofing.

What is a French drain in a basement?

A French drain (also called a weeping tile, drain tile, perimeter drain or sub-surface drain) is a common basement waterproofing solution. It's a trench containing a perforated pipe that redirects surface water and groundwater away from the foundation.

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