WATERPROOFING
BASEMENT WALLS
Anyone who has ever experienced a wet basement understands the importance of waterproofing basement walls. According to the American Society of Home Inspectors:
Most new homes will develop a basement leak within 10-15 years of being built.
Over 60% of basements in existing homes have a moisture problem.
Over a 30-year mortgage, you’re five times more likely to experience a basement leak than a fire in your home.
Perhaps most importantly, water leakage and mold can decrease the value of a property by 25%.
All of this shows the importance of keeping your basement dry and waterproof. This guide will walk you through the steps required to waterproof your basement, from the simplest to the most advanced options available to you.
FIND THE
SOURCE
The first step if you have water coming in through the basement walls is to find the source of the leak. If your basement walls are concrete – which is porous – identifying the specific area of the leak should be straightforward.
The best places to look for streaks of wet or dampness on the walls are:
- Near cracks in the concrete
- Around the edges of windows
- Between mortar joints
- Where pipes enter/exit your basement
- The cove joint (where the wall meets the floor)
RUN A FOIL TEST:
In more extreme cases, such as an entire wall being wet, you’ll need to run a ‘foil test.’ To do this, take the following steps:
1
Dry the Area
Dry the wall with a rag.
2
Cover with Foil
Duct tape a one-foot by one-foot piece of aluminum foil to the dry wall – making sure the seal is tight
3
Wait 24 hours, Then Check
Remove the foil after 24 hours and check the underside (i.e. the side that has been in contact with the wall).
If the foil is wet, water is seeping through the wall from outside. If the foil is dry, the moisture is coming from somewhere else in the basement. In this instance, it is most likely caused by condensation from something like a washer-dryer or a shower in the basement.
DRY THE
BASEMENT
Once you’ve found the source of the leak, you’ll be able to work on stemming the flow of water. However, before you proceed with any work, you need to dry the basement – particularly if there is standing water present. Standing water greatly increases your chances of receiving an electrical shock while working.
Shut Off Electricity
The first thing to do should be to turn off the electrical power to your basement. It is unsafe to put any part of your body in standing water that with an electrical charge running through it.
If your electric panel has been compromised or you can’t safely reach it, then call in professional help.
Remove Water
Then use a sump pump or utility pump to remove the standing water a safe distance away from your home.
- The cost of renting a submersible utility pump is around $50 per day or $190 for a week. You can also purchase a good quality sump pump for $140 - $360.
Dehumidify
You can also use a dehumidifier to fully dry the surfaces within your basement. This will make it easier for waterproofing paint to adhere to surfaces.
- To rent a large dehumidifier, you can expect to spend around $50 per day or $170 per week.
Our guide on the best dehumidifiers for your basement ranks and compares the top dehumidifiers available today.
FILL CRACKS IN
WALLS AND WINDOWS
Hydraulic cement is an at-home solution to filling in cracks in the walls of your basement. Hydraulic cement expands as it dries, which fills any cracks to create a fully watertight seal. A 10 lb. pail of hydraulic cement costs roughly $15, making it an easy and cost-saving option.
To use hydraulic cement:
Mix Cement & Water
Mix the hydraulic cement with water (for exact ratios, see the instructions on the pail). Note: only mix the amount of hydraulic cement that you can use in three minutes or it will begin to set in the container before you apply it to the wall).
Apply to Crack
Press the cement/water mixture into the cracks in the wall. Use a putty knife or gloved fingers to get it deep into the cracks.
As the hydraulic cement expands, it will prevent further leaks. However, you should also take steps to prevent water from placing pressure on your basement walls. This may include things like re-grading your yard or installing French drains (see the section below on Exterior Waterproofing).
WINDOW WELLS
Another major source of leaks in basements is through the window wells. Because basement windows largely lie around ground level, water can easily accumulate and begin to seep through.
The three main options, if you do have leaking through a window well, are to:
- Dig a new well. Dig a two-foot well area immediately outside the window and fill the well with gravel. This will allow rainwater to disperse rather than pool.
- Add caulk. Add an extra layer of caulk to the edges of the window joist.
- Get a well cover. Install a sloped window well cover to deflect the rain away from the window.
Your best choice may be to do all three of the above. You can complete all three projects in a single day without additional labor needed.
INTERIOR
SEALING
Sealing the interior walls of your basement is a far cheaper (and easier) option than sealing the outside. If you do pursue this option, you have four products to choose from:
Concrete Waterproof Coatings
With concrete waterproof coating, you brush the mixture onto your walls – either concrete or masonry) and it dries to adhere permanently to the surface. This creates an impermeable membrane, meaning that water cannot leak through your walls.
Although the name may imply a functional, boring finish, you can ‘brush’ the surface as you paint to give it a professional finish.
- Limitations: If your basement wall has already been painted, you will need to sand off the paint before you apply the concrete waterproof coating.
Cost: A 5-gallon bucket of concrete waterproof coating is between $30 and $40 and will cover 100 square feet.
Silicate-Based Concrete Sealers
These types of sealers absorb into the wall and react with the concrete or brick to form a waterproof barrier. They are sometimes known as densifiers because of their ability to make walls ‘thicker.’ Key benefits of this type of sealer are that it won’t flake off or peel and it doesn’t leave a residue or finish on the basement wall.
- Limitations: If your wall has already been painted or sealed, silicate-based sealers won’t work.
Cost: A 1-gallon can costs $40-$50 and will cover 200 square feet (although you need to do two coats).
Waterproofing Paint
Waterproofing paint looks and acts like regular paint – you roll or brush it onto your basement wall; in some cases, you can even spray the paint onto the wall. However, unlike regular paint, it is designed to keep water from passing through.
Moreover, waterproof paint is much thicker than regular paint and requires a lot more paint to cover much less area.
- Limitations: Waterproof paint doesn’t prevent water from getting into the basement walls. If water does get in, it can quickly ‘push’ the paint off the walls.
Cost: A 1-gallon can of waterproof paint costs $35, but will only cover 75 square feet.
Plastic Sheets or Panels
This system is the most technical and may require additional labor. The first step is installing plastic sheets or panels to the wall. These panels then allow water to drain down to the basement floor without passing through them. A sump pump then pumps away the water that accumulates.
- Limitations: The main limitation here is that water still gets into your basement, although the items in your basement are protected. It, therefore, combines the cost and difficulty of an exterior waterproofing job, with the key ineffectiveness of an interior waterproofing job.
Cost: This is the most expensive option. The panels and the pump together will cost between $3,000 and $5,000 for a standard, 20×20 foot basement.
EXTERIOR
WATERPROOFING
If you want to make absolutely sure that your home is waterproof, then exterior waterproofing is by far the best option. This involves placing waterproof lining around the exterior of your basement wall. Although this is a drastic solution, it has the added benefit of preventing water from permeating the walls at all, thereby preventing structural damage. This option is very much a permanent solution to the problem.
In addition to the waterproofing, you may also look to install a French drain around the outside of your home to further prevent water from building up.
However, while many of the other solutions can be run in combination with one another, if you use exterior waterproofing, there is little need for any other waterproofing to take place.
- Limitations: The primary limitation of this type of waterproofing is the cost. However, there is also the disruption caused by the need to dig a trench around the entirety of the perimeter of your home. This can be exacerbated if you have tree roots, gas lines, or any other underground obstacle.
Cost: The cost for the full excavation, the materials, and the labor will come in between $15,000 and $30,000.
Since there’s a very strong chance you’ll experience basement leakage at some point in your future, it’s better to know your options. Waterproofing can run from an hour’s work and $30 to a week’s work and $5,000.
Deciding which choice is best for you is a matter of timing and circumstances. But know that it’s better to think long-term rather than short, and see any spending as an investment into your home.