Rising damp specialists in Battersea and Wandsworth

Waterproofing Strategies for Basement Extensions in London

Do you want more space in your home? If you have a basement, you can convert it into liveable or usable space to add more space to your home. There are varying levels of conversions, from simple to elaborate ones, depending on how much space you have, your budget, and other factors.

Even though it may seem like a project without too many complications, there are several things you need to deal with before doing a basement conversion. One of these things is to waterproof the area. Because they lie below the ground, basements are typically damp, which introduces issues such as rising and penetrating damp and the possibility of mould growth.

If you want to convert your basement, here are some of the best strategies to waterproof and keep it dry.

Do a Survey First

Before looking at the different basement waterproofing strategies you could use, you should first find the source of moisture in your basement. Each home and basement is different, so a solution that works on one might not work on another.

A waterproofing specialist can complete the survey for you, and they may even let you know of additional issues that you need to take care of before starting the conversion. For example, they may notice signs that the basement walls will crack and cause moisture issues in the future. They can provide solutions for these and other issues.

Basement Waterproofing Strategies

The different waterproofing strategies are divided into various categories depending on where and how they are used.

Using Interior Sealants

One of the most common water entry points in a basement is through cracks in the walls. The good news is you can seal those cracks from within. You can do this through sealants and epoxy sealants injected into the cracks. These fill the crack up to the exterior opening, closing the space water would have used to seep into the basement.

These sealants and epoxies last a very long time and are a great solution if you do not have a severe water problem or larger cracks. If you do, you will have to explore other options. Also, they do not work well if there is a lot of water pressure on the outside pushing on the basement walls.

Use Waterproof Coatings

Waterproofing coatings are also a good idea if you do not have a serious issue with cracks, subsidence, or water pressure. These coatings adhere well to concrete walls and are perfect for basements with minor condensation and moisture issues.

However, they cannot fix damp issues caused by basement floods or major leaks; you must find a more robust solution for them.

Apply Basement Tanking

Tanking uses a slurry to create an impermeable waterproofing coating which can be used on both floors and walls. Because of how easy it is to use and how great it works it is a great option for basements with severe damp issues.

Tanking slurry, also called cementitious tanking, uses a mixture that is applied to walls to stop water egress. Most contractors buy it as a powder that they mix on-site using clean water, but you can also buy it as a pre-mix to make things easier.

This mixture contains chemical modifiers, aggregates, and Portland cement that give it water-sealing properties. Some also include acrylic polymers that give it additional abrasive resistance, strength, and bonding power.

Once you have prepared the mixture, apply two to three coats to the basement walls and floor, letting each dry as you go.

When it is dry, it can be plastered before the conversion or decoration. Do not paint the tanking directly or use decorations that block moisture because doing so will lead to issues down the line.

Apply a Damp Proofing Membrane

These membranes can be used on top of tanking or alone to prevent penetrating damp. These materials consist of studded polypropylene that is impermeable to water. They are easy to install and are installed in such a way that there is a cavity left behind them and their studs face inward.
Water can enter the cavity and drain. However, there are instances where there is so much water or so little natural drainage that it needs to be pumped away. If this is the case in your situation, the contractor will install a sump pump that you can use to direct the water away from the house, typically into an external drainage solution.
Once installed and secured, the contractor can plaster or dry-line the membrane before you can decorate the item. Alternatively, you could paint the membrane to ensure the extension matches the rest of the house much better.
Besides wall membranes, the contractor will also install floor membranes. These perform much like their wall counterparts and ensure water cannot seep into the converted basement through the floor. However, they have bigger studs, so they stay in place better.
Lining both the walls and floor with membrane is an excellent solution for those who want their conversion to finish faster. You do not have multiple layers of material to worry about like you would with tanking. You only need to wait for the plaster or paint to dry before continuing your project while you would have to wait for multiple coats of tanking to dry before continuing.

Combine Different Approaches

Sometimes you have an issue where one waterproofing option does not work. For example, you know how well tanking works but do not want to be limited in your decorations. You can turn to sealants, but then you have a water pressure issue.

In these and similar cases, you should consider combining methods. You could use sealants to deal with cracks and a waterproof membrane for more serious areas of water ingress.

Every property or homeowner who wants to convert a basement into a liveable space has to find ways to deal with damp. The good news is that there are numerous waterproofing options that you can use, some more elaborate and require more preparation than others. Always consider your specific circumstances and project to ensure you use strategies that work best for the long term.

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