If you are building a foundation for a concrete house, or have a house built largely of concrete, you may find yourself considering waterproofing the concrete itself to keep the rooms inside dry and cozy. It must be said that concrete itself is more impermeable than other materials used for building structures, and normally the only attention in this regard is required for cracks, joints, doors and windows. Read the first step of this guide on the first considerations to make, and which waterproofing techniques can be taken into consideration.
Steps
Method 1 of 3: Prepare the Surface
Step 1. First of all, evaluate if the waterproofing operation is really necessary in your case
Buildings with pre-formed concrete walls, prefabricated panels or ICF concrete with integrated insulation are essentially more waterproof than constructions made of other materials, so they need less attention from this point of view. However, it must also be said that the cladding of prefabricated concrete panels often has more an aesthetic function than a really waterproofing one.
If you think the structure in question really needs waterproofing, ask a construction company for specific advice. They may suggest that you just apply liquid sheathing, better seal joints, or fill in any cracks rather than embark on a more complex total waterproofing job
Step 2. Prepare the walls for the chosen type of cladding
If you have decided on waterproofing, the walls will need to be prepared properly, regardless of the technique used. This means:
- Seal with a good polyurethane sealant - to fill expansion joints and cracks up to 6-7mm wide.
- Fill open joints more than 6-7mm wide with concrete - making sure it is dry before proceeding.
- Smooth - to make the surface uniform, in order to facilitate the adhesion of the waterproofing layer, or of the mixture chosen for the purpose.
Step 3. Clean the concrete surface thoroughly before waterproofing
With a wire brush, trisodium phosphate and water, wash the wall thoroughly, removing any crumbly material, dirt, and any oils present on the cement surface. Most coatings need a well-cleaned surface to adhere. Let it dry well before proceeding.
Method 2 of 3: Choose the Right Waterproofing Product
Step 1. Use a liquid sheath if your priorities are speed and economy
Liquid sheaths are usually polymer based and can be sprayed, or applied directly to the wall with a trowel or roller. They have the advantage of being quick to apply and relatively cheap. Be sure to read and follow the product instructions for use.
The disadvantage of liquid sheaths is that they do not allow for uniform coverage. Even if you were to opt for 60mm coverage, the recommended minimum, it's hard to get the same thickness everywhere
Step 2. Use a self-adhesive membrane if you want a more even coating
Self-adhesive membranes are large rolls of material composed of rubber and asphalt, which are applied directly to the concrete wall after removing the protective part that covers the adhesive side. They guarantee uniformity of coating thickness: however, compared to the liquid sheath, it is a more expensive method (both for the cost of the materials and for the work required) and more complex.
- This type of membranes have a very high adhesive strength, and it is essential to handle them with extreme care after removing the protective material: once they have adhered to a surface it is virtually impossible to detach them.
- Pay particular attention to how the membranes intersect - if the job is not done carefully, leaks can later be created. Make sure the overlap joints are cut neatly, and seal them well with putty if they are less than a foot or so from a corner.
- At least two people are required to apply a self-adhesive membrane. Trying to do it yourself is a good recipe for poor quality work, and for a good deal of unnecessary frustration.
Step 3. Also take into consideration the "Coating" Waterproofing Plaster (EIFS)
It is a durable and easy to apply product, and useful for both insulation and waterproofing. EIFS can be applied as a putty directly on concrete to fill cavities, smooth out irregularities, and create a moisture resistant coating.
EIFS plaster is applied with a trowel, and is usually available in buckets containing the product ready for use and in different colors. Apply it with a polystyrene block or a rubber trowel to create a smooth, even coating. Some specific EIFS products can be applied with a brush or roller to paint, or even sprayed
Step 4. Try to use cementitious materials for waterproofing:
they have the advantage of being easy to mix and spread. They can be purchased in building supply stores, mixed with an acrylic additive to improve grip, and can be applied with a large, long-handled brush. The only disadvantage is that they have no elasticity, and are therefore prone to crack over time.
Step 5. If you prefer an ecological and non-polluting waterproofing method you can opt for sodium bentonite
Sodium bentonite is used in landfills in many cities to prevent liquids from seeping into the ground below. It is essentially clay, has excellent waterproofing properties and is a good option for limiting the human footprint on the environment. It also has the advantage of being able to be applied equally on more or less smooth surfaces.
Method 3 of 3: Finishing and Final Considerations
Step 1. Before starting, decide which walls you will want to waterproof, in order to optimize time, money and effort
A good starting rule is to waterproof the walls that delimit a habitable area (also including any spaces containing cables or pipes) and border on the outside. Other considerations can be:
- If the house is located in a particularly humid area, it is probably best to waterproof all the walls.
- When waterproofing a wall, do not be too precise on the edges but extend the chosen treatment by about 30 cm on the neighboring walls (even if they are not to be completely waterproofed): in this way you will be sure to cover the entire surface of the chosen wall well.
Step 2. To get the best result it is important to carefully follow the specific directions and advice on the product you will choose to use, by reading the instructions or by asking an expert
Step 3. Use a roof-specific method in the case of a poured concrete roof
Although they are not common, there are buildings with roofs built in this way, and generally in these cases a continuous concrete roof and a mat in reinforced fibers, prevent the infiltration of water.
If the roof does not have a sufficient inclination to drain the water away, it is advisable to apply a synthetic or bituminous membrane, or a continuous polymeric type cover. These are techniques normally adopted by construction companies, to which it is best to turn for this type of work
Step 4. Remember to pay attention to the water drainage system, as well as think about waterproofing techniques:
waterproofing alone is of little use if the water does not drain properly. Consult an expert on whether to build a ground-level drain, an underground drain, or even, in the presence of large volumes of water, a sump pump that takes water from the ground and redirects it elsewhere. If it's a cellar or basement, you can check out this article.
Advice
- Underground constructions are more problematic when it comes to waterproofing. Many cellars or basements are built in areas where snow often accumulates, or subject to continuous water infiltration: in these cases the high level of humidity makes it necessary to use pit pumps and dehumidifiers.
- Consult the indications on the emission of VOCs (volatile organic compounds) of the chosen products, to make sure that they comply with the law.
Warnings
- Read and follow the manufacturer's directions and manuals carefully to reduce the risks from volatile chemicals, fumes and other health hazards during application.
- Use safety gear like goggles and face masks.
