How much does basement tanking cost in the UK?
Basement tanking costs £8,000 on average in the UK. Most jobs fall between £2,500 and £20,000 for the job. Size and system: Small cellar £2,500 to £6,000; Average basement with membrane £6,000 to £12,000; Large or full system with pumps £12,000 to £20,000. Prices reviewed July 2026.
Basement tanking usually costs between £2,500 and £20,000 in the UK, with an average basement around £8,000. Cementitious tanking is cheaper per m2 than a cavity drain membrane with a sump pump, and the size of the space is the biggest factor.
Basement tanking cost calculator
Use the calculator to price your basement tanking in 2026. Adjust the options and area for a UK cost range. Nothing is sent anywhere.
Basement tanking cost breakdown
Typical basement tanking costs, by option:
| Size and system | Typical UK cost |
|---|---|
| Small cellar, cementitious | £2,500 to £6,000 |
| Average basement with membrane | £6,000 to £12,000 |
| Large or full system with pumps | £12,000 to £20,000 |
What's included in the price?
Typical basement tanking prices include:
- A damp and water survey of the basement or cellar
- Preparing and sealing the walls and floor
- Cementitious tanking slurry, or a fitted cavity drain membrane
- A sump and pump where a drained system is used
- Making good and clearing away afterwards
What changes the price?
The things that move basement tanking prices most:
The size of the basement in square metres
Whether it is cementitious tanking or a cavity drain membrane system
Whether a sump and pump are needed
The condition of the walls and how much prep they need
Access and how far below ground the basement sits
These are why two quotes for the same job can differ, and the only way to know your price is to get prices from local firms (through Bark; we may earn a fee, at no extra cost to you).
How the price is built up
The price covers the survey, prepping the walls and floor, the waterproofing itself, and any sump and pump. A drained membrane system with a pump costs more than a cementitious slurry, and going deeper below ground adds labour and prep. Labour is the bigger share of a tanking job. Materials such as the slurry or membrane, plus any sump and pump, are typically 30 to 40 percent of the total, with skilled labour making up the rest.
Ways to keep the cost down
- Fix the source of water outside first, such as gutters and drainage, so you are not paying to hold back avoidable damp
- Get quotes from CSSW-qualified waterproofing specialists and compare like for like
- Tank the basement while it is already being converted, so the prep work is shared
Does where you live change the cost?
In London, basement tanking typically costs around £9,600 for the job, about 20% above the UK average of £8,000. In the North, Scotland and Wales the guide figure is nearer £7,800.
| Region | From | Typical | Up to |
|---|---|---|---|
| Midlands / East (UK average) | £2,500 | £8,000 | £20,000 |
| London | £3,000 | £9,600 | £24,000 |
| South East / South West | £2,600 | £8,400 | £21,000 |
| North / Scotland / Wales | £2,400 | £7,800 | £19,500 |
Guide prices for the job, scaled with the same regional multipliers as the calculator. Not quotes.
Basement tanking cost in major UK cities
| City | From | Typical | Up to |
|---|---|---|---|
| Belfast | £2,400 | £7,600 | £19,000 |
| Birmingham | £2,500 | £8,000 | £20,000 |
| Bristol | £2,600 | £8,400 | £21,000 |
| Cardiff | £2,400 | £7,800 | £19,500 |
| Edinburgh | £2,400 | £7,800 | £19,500 |
| Glasgow | £2,400 | £7,800 | £19,500 |
| Leeds | £2,400 | £7,800 | £19,500 |
| Liverpool | £2,400 | £7,800 | £19,500 |
| London | £3,000 | £9,600 | £24,000 |
| Manchester | £2,400 | £7,800 | £19,500 |
| Newcastle | £2,400 | £7,800 | £19,500 |
| Sheffield | £2,400 | £7,800 | £19,500 |
City guide estimates, scaled by local labour costs. Indicative averages for basement tanking, not quotes.
The South East and London run higher than the Midlands, the North and Scotland, where specialists and labour cost less.
Compare this with a real quote
The figures above are guide prices. Two or three quotes for your basement tanking tell you what it costs where you live.
Free and no obligation. You answer a few questions on Bark, local pros get in touch, and you decide who, if anyone, to hire. We may earn a fee, at no extra cost to you.Common questions
How much does basement tanking cost in 2026?
In 2026 basement tanking usually costs £2,500 to £20,000. A small cellar with cementitious tanking is around £2,500 to £6,000, an average basement with a cavity drain membrane and sump is roughly £6,000 to £12,000, and a large or full system runs £12,000 to £20,000.
What changes the price of basement tanking?
The two main systems drive most of the difference. Cementitious tanking seals the walls with a waterproof slurry at around £50 to £90 per m2. A cavity drain membrane lets water in behind a studded membrane and channels it to a sump and pump, costing £80 to £150 per m2 but coping better with high water pressure. Size, wall condition and depth below ground do the rest.
Is basement tanking worth it?
If the basement leaks or feels damp, tanking is usually worth it, both to make the space usable and to protect the structure. A dry basement is also the starting point if you later convert it. It only pays off when the work is done properly and the outside source of water is dealt with too.
Can I tank a basement myself?
Cementitious tanking on a small, sound cellar can be a DIY job for a confident person, with materials at £15 to £30 per m2. But if water pressure is high or the job is done wrong, you can trap damp and cause worse problems. A cavity drain system with a sump is best left to a specialist.
How long does basement tanking take?
A small cellar takes about 2 to 4 days. An average basement with a membrane and sump usually takes 1 to 2 weeks, and you then need drying time before decorating or laying a floor.
How long does basement waterproofing last, and does it need maintaining?
That depends which type you have, because only one of the two has moving parts. A Type A barrier system, cementitious tanking applied to the structure itself, has nothing to service: once it is on, it either works or it does not. A Type C system, the cavity drain membrane with a perimeter channel and a sump and pump, is the usual choice for a habitable basement and it is a managed system rather than a permanent fix. It needs servicing, and BS 8102 expects it to come with alarms, a battery backup and a maintenance schedule handed over to you, with access points designed in so the channel, the sump and the pump can actually be reached. A pump that has silted up or lost power is how a dry basement floods. On guarantees, a Property Care Association member can offer a 10-year insurance-backed guarantee, but that normally requires the system to have been designed by a qualified waterproofing designer rather than simply specified by the firm installing it. Across a £2,500 to £20,000 range that distinction is worth checking, because a guarantee from the installer alone is only ever as good as the installer.
Is there a cheaper alternative to tanking?
If you only have minor damp, damp proofing or improving drainage and ventilation outside can be far cheaper than full tanking. For a basement you plan to use as a living space, though, proper waterproofing is the reliable option.
Do I need planning permission or building regulations approval to tank and convert a basement?
Planning permission is unlikely, but building regulations apply to the conversion. Planning Portal says converting an existing basement into living space is unlikely to need planning permission in England, but it will where you add a lightwell, alter the outside of the house, create a separate dwelling or change the use significantly, and a listed building is likely to need consent for internal work. Building regulations apply to basement builds and conversions, covering fire escape routes, ventilation and damp proofing, so the waterproofing in a conversion is checked by building control along with the rest of the job.
Official guidance and sources
The rules and schemes referenced on this page come from these official UK sources. The price figures are Costwise's own; see how we price.
- Basements: planning permission Planning Portal · Converting an existing basement into living space is unlikely to need planning permission in England, while creating a new basement commonly does.
- Basement conversion: planning permission and building regulations Planning Portal · Building regulations apply to basement builds and conversions, covering fire escape routes, ventilation and damp proofing, and a listed building is likely to need consent.
- Basement conversion: things to consider Planning Portal · Describes the two waterproofing approaches: a waterproof cement system applied to walls and floors, or a membrane that lets water in and channels it to an exit point.
Cite this data
These figures are free to use in articles, reports and research under a CC BY 4.0 licence. All we ask is a credit to Costwise, and online a link. Where your style allows, please make "Costwise" the linked word so readers can check the figure for their own region.
Costwise (2026): Basement tanking typically costs £8,000 in the UK, ranging from £2,500 to £20,000 for the job. Reviewed July 2026. costwiseuk.co.ukSource: Costwise (costwiseuk.co.uk)Costwise (2026). Basement tanking cost. Costwise UK cost data, version 2026-10-12. https://costwiseuk.co.uk/basement-tanking-cost/2026-10-12 (158 jobs)Dataset DOI: 10.5281/zenodo.21159943 · also on Kaggle, Hugging Face and Figshare. Method: how we price. Downloadable CSV.
These are independent guide prices based on typical UK jobs in 2026. Your actual cost depends on your property, spec, access and where you live. Always get at least three written quotes before committing.