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Is Waterproofing Membrane Necessary

Whether you are finally constructing your dream home from the ground up or adding the much-needed renovation to make room for your expanding family or business, there are certain things you need to take into account that you might not have thought much about.

For instance, you know that you need to keep the inside of your home nice and dry and protected from the elements, so you will make sure you have strong walls and a sturdy roof. However, to really make sure no water seeps into your home, you might need to install a waterproofing membrane in some areas of your home.

Waterproofing is necessary in basements and foundations. It is beneficial for roofs, bathrooms, showers, and balconies/terraces. Waterproofing membrane is a good option, but it is not the only option. Alternatives are cementitious coating, rubberized asphalt (roof), and thermoplastics.

What Is Waterproofing Membrane?

You need to keep your home dry and make sure that any water outside, does not come inside. So you know you need to add a waterproofing membrane so that you can achieve this. But what exactly is this?

waterproof membrane

A waterproofing membrane is a water-tight material that is installed on various surfaces around your home to prevent leaks. These membranes come in two forms: liquid or sheet-formed.

If you choose sheet-based membraned, you will simply purchase the rolls of the Polymer-modified bitumen/ Polyurethane membrane and unroll them and adhere them to the necessary surfaces.

Liquid membrane is a “monolithic, fully-bonded, liquid-based coating applied to the surfaces by being sprayed on, or manually brushed on. It foams up and creates a seamless waterproof barrier.

Where Is Waterproofing Necessary?

According to Section R406.2 of the Internation Residential Code (IRC), which is the building code adopted by most American states, waterproofing is necessary for concrete and masonry foundations, specifically:

  • Where a “high water table or other severe soil-water conditions are known to exist”.
  • Where “exterior foundation walls that retain earth and enclose interior spaces and floors below grade”. These areas are waterproofed from the finished grade to either the top of the footing or to 6″ (152 mm) below the top of the basement floor (whichever is highest).

So, this basically means that the most important places to apply some kind of waterproofing membrane are your foundations and your basements, and there are very good reasons for this.


The foundation of your home keeps your house safe and secure, therefore, you need to take every possible measure to make sure you are doing the most to keep your house stable and safe.

waterproof foundation

Water can seep from outside and flow under your house. It can also reach your foundation if there is a flood. If there is no waterproofing, this water can cause the foundation to swell or become brittle and weak, breaking easily.

You need to apply the waterproofing membrane to the walls of your foundation, making sure the wall is smooth and any holes filled before applying it. Once the contractor has approved that the membrane is applied properly and is the appropriate thickness, then an additional layer of insulation is applied.


We all know that basements are often the poor victims of water damage as they tend to be unfinished or simply the catch-all for water. Signs that your basement may have water damage include cracked walls with peeling paint and the presence of mold.

In order to prevent floods, water damage, and structural issues in your basement, which can also affect the upstairs or above-grade parts of the home, it is best to make sure you have sufficiently added waterproofing membranes to your basement walls and floor to prevent any water from leaking through to the inside of the house.

You should waterproof the outside of the basement walls, and it can be beneficial to also waterproof the interior surface of the wall with something like Drylok.

Does a Waterproofed Basement Need a Sump Pump?

Other Locations That Benefit From Waterproofing

While the basement and foundations have to have waterproofing membranes of some kind, there are other locations of the home where it is extremely beneficial.


Your roof is literally the outermost part of your home that will bear the brunt of any water that the house is exposed to. Come rain, shine, hail, or snow, your roof will feel the elements first, so it is vital to make sure it has adequate protection.

You should install this membrane above the structural slab, but below your roofing tiles to ensure that no water can seep through and cause damage to your roof struts or attic.

The type of waterproofing membrane used needs to have specific properties due to its unique location. It will need to be UV stable as it will be exposed to sunlight for many hours a day, and be flexible and tear-resistant so that it can contract and expand with the tiles as the temperature changes.

Some types of waterproofing membrane you could consider for your roof include:

  • Self-adhesive modified bituminous membrane.
  • Thermoplastic membranes.
  • Polymer-modified bitumen membrane.

If you were to have no waterproof membrane, you would likely feel drops of rain showering on you throughout the house. Your structural slab will also become saturated with water, which can lead to mold and structural damage.

Exterior Walls

The exterior walls of your house will be faced with the elements regularly, so unless you are okay with water seeping through the walls and causing a host of issues, you will need to waterproof it.

Experts suggest applying the waterproofing membrane to the outside of the walls as this is the side that will be the most likely to be exposed to water, snow, or hail.

However, these walls will need additional waterproofing mechanisms to ensure their utmost longevity. The waterproofing membrane is more of an added protection, not the main character in waterproofing the walls.


Your bathroom is the space in your home that will be exposed to the most water that comes from within. Without sufficient waterproofing, your walls, floors, and ceiling quickly become infested with mold and become brittle and weak to the touch because of the accumulated water that has seeped into the surfaces.

bathroom waterproofing

You should apply the membrane to the walls, floor, and ceiling as the humidity from the bathroom will reach all of these surfaces, so they should be adequately protected. When it comes to the floor, you will need to carry the membrane slightly up the wall to cover the cracks and joints.

Even with waterproofing, you should still take steps to reduce the amount of moisture created or retained in your bathroom.


It is very important to apply waterproofing membrane to your shower floor as it will constantly have water washing over it. You want the water to flow neatly down the drain, and not seep into the floor.

Although your ceiling should be waterproofed throughout your house, you do need to make sure you have applied a waterproofing membrane in the ceiling above your shower, as that is where most of the steam will accumulate.


Having a balcony or terrace in your home is a real blessing as they provide additional opportunities for relaxation and entertaining.

Since these areas are outside, they too will be exposed to the elements continuously. You will need to install the waterproofing membrane on the subfloor of your balcony and terrace. The membrane has to have similar properties to your roofing membrane as it needs to withstand UV rays and temperature changes.

Water on your balcony can quickly seep through the subfloor. Too much water can make the balcony extremely brittle and poses a huge safety risk.

Make sure you have drainage systems in place in addition to your waterproofing membrane so that the balcony does not become flooded. This water can travel to the rest of your house and cause serious damage.

Downsides of Using Waterproofing Membrane

  • Sheet-based waterproofing membranes tend to be more expensive than other waterproofing options as they require higher labor and material costs.
  • They also tend to crack and break down during periods of weather change, which can result in leakages.
  • Liquid waterproofing membranes bring the risk of inconsistent coverage – one area could have a thicker membrane than the other. It is best to leave it to the professionals to ensure efficiency.
  • Sheet membranes are quite sticky due to their need to adhere tightly to the required surfaces. This means that there is little space to make errors as if you place the sheet in the wrong spot, lifting it off can cause it to tear.
  • Sheet membranes bring the risk of having visible seams and open joints where the sheets meet. This poses the risk of water leaking through.
  • They will not work optimally if they are not left to dry completely before they are covered.

Does It Have to Be Waterproofing Membrane?

Waterproofing membranes are not the be-all and end-all of waterproofing. There are there other suitable forms of waterproofing that can be used.

You can make use of Cementitious coating, which is often used by contractors because of how easy it is to apply to surfaces as well as its affordability. However, unlike waterproofing membranes that can be used in a variety of locations, cementitious coating is less flexible and more suited for basements and foundations.

For your roof, you can make use of Rubberized Asphalt as it is extremely tough and flexible and will definitely prevent any water leaks through your roof.

Another option, albeit slightly costlier, is thermoplastic. When this material is heated, it becomes liquid, which allows it to be applied to seals and walls.


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