How to Waterproof a Cellar
Many homes in the UK have a cellar or basement space underneath the ground floor of the property. This might be small, such as a coal vault that was designed mainly for storing coal and food in the Victorian times, or your cellar might span the entire width and length of your home. Either way, they can make ideal additional storage spaces for your belongings, or in the case of a large basement, be converted into an additional living space that can be used as a home office, extra bedroom or living room, games room, or even a whole apartment to rent out.
The truth is, however, that many cellars in the UK are not used as much as they could be due to damp issues. Since the cellar is below the ground level there is a lot of earth around the exterior walls with moisture that gets through easily if the cellar has not been waterproofed. This could mean that when you moved into your property, excited to use the cellar for storage, you were disappointed weeks later when you went to get your belongings only to find that they had gone damp and mouldy.
Whether you just want a useable storage area or are hoping to turn your cellar into another room, here are the main options for waterproofing your basement or cellar.
Waterproof Render and Damp Proofing
One option to consider is a waterproof render. This is usually applied on the external walls of a property but can also be used in your basement to provide a water-resistant coating that prevents moisture from getting through and causing damp.
Waterproof Render and Damp Proofing in London
A waterproof render such as a silicone render can be used in your cellar for waterproofing and preventing damp. This is a good idea if you are going to use your cellar for storage rather than as a living area since waterproof render is durable and doesn’t require much maintenance or touching up over time. Silicone render is the best option and since this is typically designed for using on the exterior walls of a property, you can get it in several pre-mixed colours of your choice.
What is Waterproof Render and Can You Get Waterproof Render?
Silicone render is the best choice if you are looking for a type of water-resistant render to use for waterproofing your cellar or if you want a coating to apply to the exterior walls of your property to increase water resistance and prevent problems with penetrating damp inside the home.
Will Waterproof Render Stop Damp?
Waterproof render is designed to be impenetrable by moisture so it can be a very effective product when it comes to preventing penetrating damp. Penetrating damp is a type of damp that gets in through the exterior walls. In the basement, this is usually water that has accumulated in the ground around the walls since the basement is below ground level. On the exterior walls of your home, it is more likely to be an issue caused by heavy rain.
What Do You Use to Waterproof Render?
If you’ve decided that rendering is your best option in the cellar, then you should look out for a silicone render. You may also be able to find silicone that you can add to traditional render that comes in a powder and is mixed on-site with water. You can also add waterproofing properties to existing non-waterproof render with the help of waterproofing façade creams.
If you are serious about sealing your basement before using it as storage or turning it into a liveable space, then a better option that you might want to consider is cement tanking. This involves applying a waterproof slurry which is used to coat the walls and, in some cases, the floor and ceilings of the basement to prevent any moisture from getting in. Since it is applied directly to the masonry, it provides a sealant that stops water from getting in through the brick or stone at all.
This can cause a lot of external water pressure to build up around the walls, so it is important to make sure that your cellar is adequately prepared for the slurry to be applied. You should do this by removing any wall coverings that are currently in place including any existing rendering, plastering, paint, or wallpaper and then conducting necessary repairs.
A salt-neutralising product may be applied to the bricks to prevent salt deposits in the future that could damage the structural integrity. Along with this you should repoint the bricks if necessary and make sure that any cracks or other types of damage are repaired.
Cement tanking is usually your best choice if you have low-level damp problems in your basement. It can be used to seal the entire basement or used in single problem areas that need additional protection.
How is Cement Tanking Applied?
Once the preparation has been done, the hardest part of this job is over. Cement tanking is usually applied as a slurry directly to the masonry substrate such as brick, stone, or concrete. Before you apply the slurry, it is a good idea to prime the area, which you can do with a specialist priming spray. Or, if you are dealing with materials such as waterproof concrete that do not provide a good key for the slurry to adhere to, then you may want to start by first applying a bonding slurry, which will provide the necessary key and make it easier for the cement tanking slurry to bond to the substrate and prevent moisture from entering in the future.
Cavity Membrane Drainage System
A cavity membrane drainage system is a good choice for damp proofing a basement or cellar that is prone to damp. This is a high-density Polyethylene, a studded and waterproof membrane that is fitted to the floors, walls, and perhaps the ceiling of the basement depending on where waterproofing is needed. Unlike with cement tanking, you can install it over existing wall surfaces such as plaster and paint, so there is less preparatory work needed.
The membrane system works in a different way to tanking. Instead of preventing the moisture from getting in through the walls completely, the membrane blocks it in a cavity between the wall and the membrane, where it can be drained away. The water is drained down into the floor cavity where it goes through a drainage system, often involving a sump pump that removes it from the basement and out to an external drain.
This type of waterproofing can be a better choice for basements that are prone to flooding or have bad damp problems, as it is a way of controlling the moisture that is coming through rather than completely blocking it out. This means that there is less pressure on the external walls of the basement, and less risk of damage from high levels of moisture.
How is a Cavity Membrane Drainage System Installed?
Unlike with tanking, which is a job you can do yourself with a little bit of DIY knowledge and skill, you will need to hire a professional to come and install a cavity membrane drainage system in your basement. It’s a good idea to find a professional installer who has a good knowledge of the entire installation process and the different membrane specification to help you find the right one for your needs.
The main reason to invest in professional installation for this job is that even the smallest of errors during the installation process can cause big problems in the future, and this isn’t a risk that you will want to take, especially if you are going to turn your cellar into a habitable room for your home. Weak patches in the membrane are easy to overlook if you are not an expert, and this can cause the entire system to fail in the future, as water pressure will build up around these weak areas and cause flooding and serious damage.
Can You Use Two Options Together?
Yes. If you want even more protection from damp and flooding in your basement, then you can use two different options at the same time. For example, a cement tanking slurry can be applied to the masonry substrate first, or a waterproof render can be used before installing a cavity membrane system to provide drainage and additional protection against any water that might make its way through the external walls. This might be recommended if your cellar is very prone to severe damp problems or if you have had instances of flooding in the past.
In cellars that are prone to flooding, cement tanking slurry or waterproof render alone might not be enough to prevent the issue as while moisture is blocked, the pressure will continue to build up around the external walls with nowhere to go, which can lead to more serious issues.
Whether you just want more storage space or are considering converting your cellar into another room, it’s important to understand the damp-proofing options available.
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