If your home has a significant amount of concrete or you are building a foundation of concrete, waterproofing is a way you can ensure your home stays comfortable and dry. As a rule, concrete homes are already more waterproof than other types of homes but may need attention in places where there are window and door openings, joints, or any other cracks or openings.
This article will help you waterproof your concrete home and learn more about the techniques involved.
Does your home need waterproofing?
If your home was constructed with precast concrete panels, core-formed concrete, or Insulated Concrete Form (ICF), you will likely not need to do anything extra because these methods are usually more waterproof than other methods. However, weatherproofing on pre-fabbed concrete is usually there for looks and not function.
A general contractor can help you decide whether your home needs additional waterproofing. You may not need a full-on waterproofing job, but often adding a liquid membrane or filling in joints and cracks is enough.
Preparing the walls for coating: Regardless of the waterproofing technique you have decided to use, you concrete walls need to be in good condition.
Before you waterproof your concrete, you need to clean it completely: Clean oil, dirt, and any other loose material with trisodium phosphate (TSP) and water with a rigid brush. You will need a clean and dry surface for the waterproofing to stick.
A liquid membrane is the fastest and most economical waterproofing tool. Polymer-based coatings can be applied directly to the concrete with a roller, a trowel, or with a sprayer. Be sure to follow the instructions provided by the manufacturer.
Unfortunately, liquid membranes do not go on evenly, and it’s sometimes difficult to get the recommended 60 mm of coverage.
A self-adhering sheet membrane is a large rubberized asphalt membrane that you just peel and place onto the concrete, making it easier to achieve a consistent application. This method is more costly to purchase and installation takes longer because the process takes time to get used to.
Because the sheets are so sticky, you have to take your time during installation to keep the sticky side of the membrane from touching anything other than the concrete itself.
During installation, pay special attention to how you place the sheets to avoid leaks. Lap joints must be cut properly and a bead of mastic should be applied to every lap joint within 12 inches of the corners.
You will have a hard time installing sheet membranes by yourself, so you will need at least two people to get the job done right and avoid a lot of frustration.
For a better-looking, more durable waterproofing option, try exterior insulated finish systems (EIFS), a simple coating that doubles as waterproofing and insulation. An EIFS looks like stucco and is applied to the outside of the concrete and will seal any voids, float out small abnormalities, and create a moisture-resistant surface.
EIFS is premixed in a 5-gallon bucket and tinted to the color of your choice.
You can apply it with a trowel, but some products may be applied with a brush, sprayed on, or you can use a paint roller. Use a Styrofoam block or rubber float to add texture or to achieve a smooth, even surface.
Found at your local masonry supply store, cementitious waterproofing is an easy to mix and apply option. To get a better bond and easy application, mix with an acrylic additive and apply with a long-handled brush. Unfortunately, cementitious waterproofing tends to crack over time because of its lack of elasticity.
For a “green” method of waterproofing, use sodium bentonite, a type of clay that can cover coarse and smooth surfaces. If leaving a human footprint is a concern of yours, sodium bentonite is a good waterproofing option. Many city dumps use it to prevent liquid from getting into the soil below.
Decide which walls you need to waterproof. In order to save time and money, know ahead of time which walls actually need to be waterproofed. As a general rule, you want to waterproof the walls that have soil on one side and are living in on the other. Don’t forget about your crawl space! Consider the following when making a decision:
You may want to consider waterproofing all of your walls if you live in an area like Seattle that is particularly wet.
Give the waterproofing a buffer by applying it an extra 12 inches onto the walls that are not being waterproofed.
Always follow the manufacturer’s instructions when applying to waterproof. The manufacturer will offer best practices and suggestions based on the method you are using. For best results, follow these instructions or contact a professional for assistance.
If you have a cast-in-place concrete roof, apply a roof sealer. Although not typical, some homes have cast-in-place roofing systems, which often have roofing cement and roll roofing that is fiber reinforced to prevent it from leaking. You may have to use a seamless rubber roofing system or apply tar or synthetic waterproofing membrane to the concrete if your house doesn’t have enough slope to drain when it rains. Keep in mind, these products are better left to the professionals to install.
In addition to waterproofing, you should make sure you have proper drainage. If you do not have proper drainage, when the water rolls off the walls, your waterproofing is not as effective. You can install a footing drain around the perimeter, an under drainpipe system, or a sump pump if necessary. Please consult a professional for these types of installations.