• Share:

Where's the moisture coming from?

Water or moisture in basements comes from two sources. One source is indoor humidity that condenses on cold surfaces, much like water droplets form on a cold drink on a humid day. The other is water—or water vapor—that comes from outside. Rainwater, melting snow or groundwater can saturate the soil around your foundation and leak in. Water can leak through cracks, or it can penetrate porous concrete or masonry walls in the form of water vapor. And basements can be wet from a combination of indoor humidity and water from outside. So your job is to figure out what’s causing the problem and, starting with the simplest fixes, work on solutions. Photo 1 shows a simple test to help diagnose your basement moisture problem. But before you go to the trouble, read the rest of this article for other clues. The problem may be so obvious that you can skip this test and get right to solving the problem.

Get rid of excess humidity

When humid air in the basement comes in contact with cool surfaces like concrete or block walls, concrete floors or cold water pipes, it condenses into water. Then the condensation drips off pipes and runs down walls, leaving your basement wet and clammy. The humid air that causes condensation can come from outdoors, or indoors from a leaking dryer vent, an unvented shower or even a humidifier left on by mistake. Water droplets forming on cold water pipes or the outside of your toilet are a clear indication that at least part of your wet basement problem is caused by condensation.

Eliminating the sources of humid air will help dry out your basement. Repair and seal your leaking dryer vent (Photo 2). Add a vent fan to your basement bathroom and make sure your family turns it on during showers. Keep your basement windows closed during humid weather. And if you’re still getting condensation on cool surfaces, run a dehumidifier to lower the indoor humidity. Air conditioning also dehumidifies air, so if you have central air conditioning, make sure the basement registers are open. Consider adding air conditioning ducts to the basement if you don’t have any.

Insulate cold surfaces to prevent condensation

Condensation dripping from cold pipes or collecting on cool basement walls can contribute to basement water problems. Reducing the humidity level in the basement is the first step, but in addition, try insulating cool surfaces. Wrap cold water pipes with foam insulation (Photo 3). Install a toilet tank insulating kit (search online for “toilet insulating kit”) or replace your toilet with one that has an insulated tank. Reduce condensation on exterior walls by insulating them (Photo 4 shows one method). But don’t cover the walls with insulation if water is leaking in from outside; you’ll just create a potential mold problem. Note: For more information on insulating, search “insulate” on this site.

Keep water away from the foundation

If your basement leaks after heavy rains or after snow melts, making sure water is diverted away from your foundation may solve the problem. It’s common for the soil alongside your house to settle over time, creating a moat that collects runoff and directs it down your foundation wall and into the basement. Lawn edging and gravel along the foundation can make things worse. The edging acts like a dam, and the gravel can hide the fact that the ground slopes toward the house (Figure A). The fix isn’t technically difficult; it’s just a lot of backbreaking work.

Start by inspecting the ground around your house to find areas that are level or sloping toward the foundation. If only one side of your basement leaks, then start your inspection on that side of the house. Figure B shows how to slope the ground away from the foundation. Unfortunately, this solution may require you to dig up existing foundation plantings, remove gravel and landscape edging, and haul in additional soil to raise the level next to the house. But it’s worth the effort because there’s a good chance this fix will prevent additional water problems in your basement.

Start by creating a 6-ft.-wide slope that drops about 4 in. away from the foundation. For extra insurance, cover the sloping soil with a layer of 6-mil poly. Then hide the poly with mulch, gravel or a layer of soil covered with grass. This will keep water from soaking in near the foundation.

Figure A: Basement Leak Problem

Figure A: Basement Leak Problem

Figure B: Basement Leak Solution

Figure B: Basement Leak Solution

Figures A and B: Basement Leak Problems and Solutions

As the soil settles around the foundation, water is channeled back towards the house instead of away from it. The solution (Figure B) is simple—add soil and create a slope away from the house.

Add gutters and extend downspouts

If your basement leaks after it rains and you don’t have gutters, consider adding them. Gutters catch the rain and channel it to the downspouts, which direct it away from the house. Whether you’re installing new gutters or already have them, be sure the downspouts have 4- to 6-ft. horizontal extensions to move the water away from the house (Photo 5).

The next time you get a heavy rain, put on your raincoat and go outside to see if your gutters are doing the job. If water is gushing from your downspouts and still overflowing the gutters, you should install additional downspouts or replace your standard 2 x 3-in. downspouts with larger, 3 x 4-in. downspouts to increase the capacity. Also notice where the water is going after it leaves the downspout. If it looks like water is pooling in the yard, one solution is to install drainage tubing that leads to a dry well.

Plug holes and cracks in the foundation

Holes and cracks in your foundation can let moisture and water seep into your basement. Plugging them probably won’t solve basement-leaking problems, but along with the other solutions we’ve suggested, it’ll help. Hydraulic cement works great for patching holes in a foundation because it can set up even under water, and it expands as it sets to seal the hole and lock the plug in place. Use a cold chisel or an angle grinder fitted with a masonry-cutting disc or diamond blade to enlarge the hole or crack into an inverted “V,” with the narrow part of the “V” on the surface of the wall. Then follow the package instructions for mixing and using the hydraulic cement (Photo 6).

Coat the walls with masonry waterproofing

If your basement leaks periodically after it rains or when snow melts, or if the aluminum foil test (Photo 1) reveals that water vapor is seeping in from outside, waterproofing the walls on the inside can help (Photo 7). Waterproofing materials that go on like paint fill the pores in the concrete or masonry walls and prevent water from leaking in. To be effective, these coatings must be applied to bare concrete or masonry walls. Start by removing loose material with a wire brush. Then clean off any white powdery “efflorescence” with masonry cleaner. Follow the safety and application instructions carefully.

A common mistake when using masonry waterproofing products is to spread them too thin. The goal is to fill every pinhole to create a continuous waterproofing membrane.

Crystalline waterproofing material is another type of waterproofing coating. It penetrates the surface and reacts with chemicals in the concrete to form water-blocking crystals. You’ll spend a little more for this option, depending on how porous the walls are. Check online for suppliers.

Install a drainage system

If you’re still getting water in the basement after sloping the ground away from the house and adding gutters and downspout extensions, then a drainage system may be the only solution. Drainage systems installed below the basement floor level on the outside of your foundation are very effective, but this approach is only practical while the house is under construction and access to this area is easy.

There are two other options for existing basements. You can buy a channeling system that glues to the floor around the perimeter of the basement. The channel diverts water that leaks into the basement into a sump pump. This system is easier to install than one that’s buried under the floor. The disadvantages are that the channel is visible above the floor, and the effectiveness of the system relies on creating a waterproof seal between the channel and the basement floor. You’ll also have to install a sump basket and sump pump.

The second option, drainage tubing below the basement floor that’s connected to a sump basket and pump (Photo 8), is more expensive and difficult to install, but it’s the best permanent fix for chronic basement leaks. You can install a system like this yourself, but breaking out the concrete floor, burying the tubing, and patching the floor are a lot of backbreaking work. Materials to do an average basement will cost $600 to $1,000. Expect to spend $3,000 to $8,000 for a professionally installed system in a standard-size basement.

Back to Top

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • Hammer
    • Cordless drill
    • Caulk gun
    • Angle grinder
    • Cold chisel
    • Dust mask
    • Wheelbarrow
    • Spade
    • Paintbrush
    • Tuckpointing tool
    • Trowel

You may need concrete cutting tools if you install a sump basket and drain system.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

    • Caulk
    • 6-mil poly
    • Aluminum foil
    • Duct tape
    • Foil tape
    • Foam pipe insulation
    • Rigid insulation
    • Hydraulic cement
    • Masonry waterproofing
    • Downspouts
    • Drainage tubing
    • Sump pump

Comments from DIY Community Members

Share what's on your mind and see what other DIYers are thinking about.

1 - 3 of 3 comments
Show per page: 20   All

August 27, 10:21 AM [GMT -5]

A quick fix done on your own may be helpful. It is better to have a professional take care of a wet basement problem. Wet basements can cause foundation structural issues and/or health issues because it can be a breeding ground for mold.

For more information, visit http://www.ebasementwaterproofing.com

August 06, 11:53 AM [GMT -5]

Flooded basement
24/7 Emergency Water and Fire Damage Specialists. Our services include but are not limited to: Fire & Smoke, Flood & Water Damage Restoration, Flooded Basement Pump-out and cleanup, Mold Removal, Sewage Backup Cleanup, Storm & Vandalism Cleanup.

May 10, 12:47 AM [GMT -5]

For around $600 - $800 you can install an above floor basement waterproofing system yourself or hire your local handy man to do it for you.


+ Add Your Comment

Add Your Comment

Affordable Wet Basement Solutions

Please add your comment

Log in to My Account

Log in to enjoy membership benefits from The Family Handyman.

  • Forgot your password?
Don’t have an account yet?

Sign up today for FREE and become part of The Family Handyman community of DIYers.

Member benefits:

  • Get a FREE Traditional Bookcase Project Plan
  • Sign up for FREE DIY newsletters
  • Save projects to your project binder
  • Ask and answer questions in our DIY Forums
  • Share comments on DIY Projects and more!
Join Us Today

Report Abuse

Reasons for reporting post

Free OnSite Newsletter

Get timely DIY projects for your home and yard, plus a dream project for your wish list!

Follow Us