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Most cellars are damp and cold places, not really good for much more than storage. Tanking a cellar can let you take advantage of that extra space. You can insulate a cellar against water and protect against damp. This makes it more usable.
The average cost of tanking a cellar can vary but it might be cheaper and easier than you think. This is everything you need to know about the process. From what material to use, to cost of hiring someone or doing it yourself, and how long you can expect it to last.
So how much will it cost? If you hire a professional, the average cost of tanking a cellar will usually range between £40-£60 per square meter. However, you can get the materials for as little as £6 per m2. So, if you’re doing it yourself, it can be cheaper.
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If you do decide to hire somebody, it is highly advised you get multiple quotes. This can help you get the best price. Job comparison sites are a great way to do this, as you get multiple quotes from rated and reviewed companies.
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A few factors are going to decide the exact price. You have to consider the cost of labour if you’re hiring someone else to do the job. This will naturally increase the average cost of tanking a cellar. As will your choice of damp proof membrane or tanking slurry.
Waterproofing your floor is another variable for the price, but it isn’t always necessary. So, while materials cost as little as £6 per m2, the actual cost can get higher based on a few different factors.
Why Would You Need to Tank Your Cellar?
Tanking a cellar essentially makes it waterproof and insulated against damp. There are a few different reasons why you might want to do this:
- Converting a Cellar – If you’re converting a cellar from storage space to an actual usable room, then tanking is essential.
- Dealing with Damp – Damp can be a problem with cellars. Tanking it prevents water from getting through in the future.
- Flooding – If your basement is having water build-up that damages what you’re storing there, tanking and waterproofing it will get things in order.
- Mould – If your basement has a problem with mould it is likely caused by damp. Tanking your basement can prevent this in the future.
These are common reasons that someone would want to tank their cellar. However, no matter why you’re doing it, the process and the average cost of tanking a cellar is the same.
Damp Proof Membrane, Tanking Slurry or Masonry Paint?
When you’re tanking a cellar, you have a choice of method. You can use a damp proof membrane, tanking slurry, or special masonry paint. Which of these you go for is going to have an impact on the average cost of tanking a cellar.
Damp proof membranes are sheets made from high-density polythene. They can be fixed to an internal wall with plugs and fitted to sit between the brickwork and your plaster. It then prevents damp or salts from soaking through.
The membrane has cavities on the inside which allows moisture to evaporate rather than soaking in. This can be fitted DIY but you’ll need to re-plaster the wall afterwards. This is one of the cheaper methods when you’re looking at the average cost of tanking a cellar.
You can see our full guide on Installing a damp proof membrane here
Tanking slurry is a thick substance that you apply to the brickwork of your wall. It is a cement-based material that needs to be brushed over the masonry. It then creates a waterproof barrier.
Tanking slurry is great for standing up to heavy water pressures. The process for applying tanking slurry is a bit more complicated. You’ll need to apply a salt inhibitor primer, then a thick layer of tanking slurry. That needs to be left to dry, then a second coat can be applied.
Masonry paint is another option which is even simpler than the previous two. This paint applied to your brickwork and will stop damp from soaking through. It works similarly to damp-proof paint for any other area of your house.
Masonry paint can be as cheap as £6 per litre, so if you’re looking for the lowest average cost, then this can be a good option.
Do You Need to Waterproof the Cellar Floor?
Tanking a basement isn’t just applying the materials to the walls. To waterproof the entire area, you might need to address the cellar floor as well. Whether or not you need to waterproof your cellar floor depends on the room’s purpose.
If you’re fully converting the basement into a useable interior room, then you’ll need to waterproof the floor. This will protect the flooring that you do lay on top. This can be done with tanking slurry or some alternatives specifically for flooring. However, if you’re just trying to stop a problem with penetrating damp then it might not be necessary. If the moisture is coming in only through the walls, then waterproofing the floor might not be needed.
Costs of Tanking a Cellar DIY
The average cost of tanking a cellar will be different depending on the method that you use. Doing it yourself is always going to be cheaper than hiring a professional. This is how the cost of materials breaks down:
- Tanking with Damp Proof Membrane – The average cost of tanking a cellar with damp proof membrane is going to be easiest with a DIY kit. These include the membrane. However, you also get the plugs, sealing washers, and waterproof taping for sealing the corners. You can get one of these kits for around £85. This type of kit will usually cover 10 m2, so that works out at roughly £8.50 per m2.
- Tanking Slurry – Tanking slurry can take longer to apply than membrane, but you get a bit of a saving. It can be bought for as little as £4.30 per m2, even accounting for the second coat. Also, an anti-salt primer will cost around £27 for 5 litres or £2 per m2. However, you will also need other tools to properly smooth the brickwork before applying the slurry. You can see a popular tanking slurry here on Amazon
You can also read our full tanking slurry review and case study here
- Masonry Paint – Masonry paint is the simplest way of doing things yourself. The average cost of waterproofing a cellar with masonry paint is about £6-7 per litre depending on the brand you go for. Accounting for using two coats, it makes the average cost of painting a cellar around £3.5m2. However, you’ll need to use a primer here too which brings the cost up slightly. One of the most popular masonry paints is Granocryl Smooth Masonry paint. You can learn more and read reviews here on Amazon
Cost of Hiring a Professional to Tank your Cellar
The average cost of tanking a cellar is going to be a bit higher if you’re hiring a professional. A general price for labour is around £100-200 per day. Depending on the size of the area and the method used it should only take 1-2 days. This time frame would be similar whether you are installing a damp proof membrane or applying a tanking slurry.
So, a rough cost will be the cost of your materials, based on the size of the job. Plus, the day rate of the person you are hiring.
If you do plan to hire somebody, it is a good idea to price the materials up yourself beforehand. This way you can work out how much you are being charged for labour.
You should also consider using online job sites to find the best companies at the best price. Our favourite is currently Bark. They have a lot of rated professionals on their website. So you can read reviews from other people that hired them.
Also you get multiple competing quotes, so you can get some real bargains. Getting quotes from local pro’s only takes a couple of minutes. You just need to click here and answer a few simple questions.
Is Tanking a Cellar a Permanent Fix?
If you’re looking at the average cost of tanking a cellar, you likely want this to be a one-off payment. Ideally, your cellar tanking should last forever, and permanently stop water from coming in. However, everything wears down over time. This is how long you can expect each treatment to last:
- Damp Proof Membrane – High-quality damp proof membrane has a life expectancy of 30 years.
- Tanking slurry – Tanking slurry is a pretty permanent addition to your home. It settles like cement. So, like cement, its lifetime more depends on how much pressure it is put under. Tanking slurry doesn’t really have a set expiry date since it works a bit differently. However, it should be last at least as long as damp proof membrane.
- Damp Proofing Paint – Damp proofing paint can be expected to last around 5 years before it starts to lose effectiveness. This is quite a bit shorter than the other ways to tank a cellar. However, masonry paint is a lot easier and cheaper to apply.
The average cost of tanking a cellar can start at £6 per square meter for materials, keeping costs low as long as you’re willing to do the tanking yourself.
There are various ways that you can tank your cellar, but each is going to give you a waterproofed room with longevity for the treatment.
Doing it yourself is possible, but it will be quite the commitment for your time. If you chose to hire someone, the average cost of tanking a cellar will increase. In either case, you’ll have a dry and damp free cellar ready for use.