What is tanking
There are two main methods for tanking: Tanking Membrane that comes in sheet form and Tanking Slurry that is chemically designed to bond with damp masonry and form a waterproof layer. The right method will depend on your exact requirements and the type of damp you are dealing with. You may also need to use a combination of these methods to ensure your walls stay dry. In the article below we aim to help you choose which is the right type of tanking for your project.
Why you need Tanking
Damp rooms often need tanking, particularly if they are below ground level. If your walls are damp, it doesn’t only cause decorative issues but can also lead to a cold home. Tanking a room can help tackle mould and damp problems, as well as stopping water penetrating your building.
When you need Tanking
If your inner walls are colder than your outer walls, condensation can form on them, and with condensation comes mould, unless you have adequate ventilation. Rising damp can also introduce salts into your wall, and because these are hygroscopic (water-attracting) it will only make problems worse. Not only do salts attract damp, drawing it from the air, but they can also leave an unsightly finish and damage the plaster.
Many people want a quick fix. However, if you’re tanking, it’s important to remove any plaster that’s been contaminated with salt as otherwise, you’re only covering the problem, not treating it.
Tanking isn’t just used in cases of rising damp. If you’re converting a basement or have an area of your home that’s below the level of your damp proof course, the walls will automatically be damp as the substrate contains moisture.
How to tank a wall
Below we give you two guides. The first explains how to tank a wall with tanking slurry and the second shows you how to tank a wall with tanking membrane.
How to apply tanking slurry
Step 1: Start by cleaning your walls, removing old plaster, dust, paint or render then wash thoroughly with water. Watch for any leaks, if water is seeping from the walls you’ll need to use a quick setting plug such as Restor Rapid Set to stop the flow until it is properly tanked. Once the wall is clean, apply Salt Neutraliser, to prevent any salts from entering the new tanking slurry you’re going to apply. Use two coats, wetting the surface with clean water between each coat.
Step 2: Once you’ve treated the wall with RUK Salt Neutraliser, fill any holes you can see with mortar (sand and cement) (NB: if you have walls made of soft stone, you may want to avoid using cement: call us for advice on alternatives). Do not use a waterproofer instead SBR Bonding agent is good and prevents damp getting through.
Step 3: Apply a coat of tanking slurry. Make sure you use the right amount of water as mistakes can make it ineffective. Once mixed, apply it to the wall in horizontal strokes, using a masonry brush.
Step 4: After you’ve applied the first coat, let it set for approximately 6 hours then apply a second coat using vertical strokes. This should help ensure you cover the wall without leaving any patches uncovered. Now, leave the second coat to cure and, once it’s totally dried out, re-plaster using renovating plaster or render with sand and cement, or paint over with microporous paint. Again SBR Bonding Agent can be used between all coats.
how to use damp proofing membranes
Damp proof membranes aren’t technically tanking, but are an efficient and simple way to damp proof below ground. They consist of a studded plastic sheet that is fixed to the wall with plugs and sealed with tape.
The studs allow air to circulate behind the membrane, and excessive moisture can be drained into a sump pump using drainage channels. The size of studs varies: as a general guide, the damper the wall, the bigger the studs, though our experts can help guide you through the different membrane types to let you know which one is right for you.
Once the membrane is applied, it can either be plastered directly onto, or battened to allow plaster boarding. You can also use membranes on damp floors.
Whichever form of tanking you use, it can help you fight water ingress, ensuring your home stays free from damp. Obviously, it’s also important to ensure you have adequate ventilation to avoid condensation related damp – but that’s another matter entirely: Condensation Analysed.
Check out our Membrane Fitting Guide.