Basement Tanking Specialists London
A damp basement can quickly become unusable, affecting both your property and its value. If you are dealing with damp walls, water ingress, or planning a basement conversion, our professional basement tanking solutions are designed to keep below-ground spaces dry, protected, and ready for use.
At Advanced Damp, we specialise in basement waterproofing for both residential and commercial properties across London, Essex, Kent, Surrey, and surrounding areas.
- ✓ Specialist basement tanking experts
- ✓ Residential and commercial projects
- ✓ Tailored waterproofing solutions
- ✓ Clear surveys with practical recommendations
CSSW Qualified Surveyors
Tanking specified by Certificated Surveyors in Structural Waterproofing.
10-Year Guarantee
Written guarantee on all new waterproofing installations.
Over 30 Years Experience
CHAS accredited contractors, fully insured for residential and commercial work.
Fixed-Price Quotations
Written specification and fixed costs following your survey, fee deducted from works.
Accredited & Trusted
What Is Basement Tanking?
Basement tanking is a Type A waterproofing system that involves applying a cementitious waterproof coating directly to walls and floors to prevent water penetration. The system bonds to the substrate and forms a continuous barrier, resisting lateral groundwater pressure.
Basement tanking is commonly used for:
- ✓ Retaining walls
- ✓ Solid brick basements
- ✓ Lower-ground flats
- ✓ Storage basements
- ✓ Utility and plant areas
When installed correctly, tanking can provide long-term structural moisture protection.
We install Newton waterproofing systems, one of the UK's leading specialist waterproofing product ranges.
Cementitious tanking slurry applied to form a bonded waterproof barrier
Is Basement Tanking Suitable for Your Property?
Not all basements are the same. Tanking may be appropriate where:
- ✓ Water ingress is moderate
- ✓ The structure is sound and stable
- ✓ There is no significant hydrostatic pressure
- ✓ The space is non-habitable or lightly used
In higher groundwater environments or luxury conversions, a cavity drain membrane system may be more suitable. A professional survey ensures the correct system is specified.
Common Signs You May Need Basement Tanking
- ✗ Damp staining to lower walls
- ✗ Efflorescence (white salt deposits)
- ✗ Peeling paint or blistered plaster
- ✗ Musty odours
- ✗ Damp patches following heavy rain
- ✗ Previous tanking failure
Early intervention prevents structural deterioration and internal damage.
Basement Tanking vs Cavity Drain Membrane
The two most common ways to waterproof a basement are tanking (a Type A barrier system) and a cavity drain membrane (a Type C drained system). Tanking blocks water; cavity drainage manages it. Here is how they compare so you can see which suits your property.
| Basement Tanking (Type A) | Cavity Drain Membrane (Type C) | |
|---|---|---|
| How it works | A cementitious slurry bonded to the wall physically blocks water ingress. | A studded membrane lets water pass behind it, then channels it to a drain or sump. |
| Best suited to | Sound structures with low to moderate water ingress and stable walls. | Higher water tables, hydrostatic pressure and habitable conversions. |
| Reliance on workmanship | High; surface preparation and application quality are critical. | Lower on the barrier, but depends on drainage and pump maintenance. |
| Maintenance | Minimal once installed, but cannot be inspected behind finishes. | Requires accessible drainage channels and periodic pump checks. |
| Typical use | Storage basements, lower-ground utility areas, retaining walls. | Basement conversions, living space, high-risk or deep basements. |
Neither system is automatically better; the right choice depends on the structure, the water risk and how the space will be used. Our survey determines which is appropriate, and on higher-risk projects the two are sometimes combined. Read more about cavity drain membrane systems or our full below-ground waterproofing systems guide.
What Affects the Cost of Basement Tanking?
There is no single price for basement tanking, because the cost depends on the property and the condition of the structure. The main factors are:
Size of the area
Tanking is priced largely by the square metre of wall and floor to be treated, so a small cellar costs far less than a full basement.
Substrate condition
Sound walls need less preparation. Crumbling plaster, salt contamination or old failed tanking that must be removed adds labour.
Preparation required
Hacking off defective plaster, treating salts and making good before tanking all affect the time on site.
System and finish
Whether tanking alone is sufficient or a combined system is needed, plus the standard of render and plaster finish you want.
As a general guide, basement tanking in the UK typically costs:
From £1,500 to £3,000
A small cellar or single-room tank, where the structure is sound and preparation is minimal.
£3,000 to £8,000
A larger basement or full wall-and-floor tanking, including preparation, render and reinstatement.
£5,000 to £12,000+
A combined tanking and cavity drain system with sump and pump, typical of a habitable conversion.
Around £20 to £30 per m²
Indicative materials-only cost if you are pricing a project, before labour and preparation.
These are guide figures only. We confirm your exact, fixed price after the survey, when we have seen the structure and can specify the correct system, and if you proceed with the works the survey fee is deducted from the cost.
Our Basement Tanking Process
Detailed Survey & Assessment
We inspect the structure, identify moisture sources and assess substrate condition.
Preparation
All defective plaster and contaminated materials are removed. Surfaces are prepared to ensure proper adhesion.
Cementitious Tanking Application
A specialist waterproof slurry is applied to walls and floors to create a bonded barrier.
Waterproof Rendering & Reinstatement
We apply appropriate render systems and finish plaster in accordance with best practice.
Each installation is carried out by experienced waterproofing technicians.
Basement Tanking for Period Properties in London
Many London basements were not originally designed as habitable spaces. Common issues include solid brick construction, lime-based mortar, lack of a damp proof course, and poor historical drainage.
Our team has extensive experience working with:
- ✓ Victorian terraces
- ✓ Georgian townhouses
- ✓ Listed buildings
- ✓ Lower-ground flats
Care is taken to ensure appropriate preparation and compatibility with existing structures.
Remedial Tanking & Failed Waterproofing Repairs
We regularly rectify failed or deteriorated tanking systems across London. Common causes of failure include:
- ✗ Poor surface preparation
- ✗ Incorrect product application
- ✗ Structural movement
- ✗ Hydrostatic pressure exceeding system capability
Where necessary, we can upgrade systems to alternative waterproofing methods to ensure long-term performance.
Why Choose Advanced Damp for Basement Tanking in London?
- ✓ Specialist structural waterproofing contractors with CSSW qualified surveyors
- ✓ All work carried out in accordance with BS 8102:2022
- ✓ Experienced in London period properties
- ✓ CHAS accredited and fully insured
- ✓ 10-year written guarantee on new installations
- ✓ Over 30 years experience
We focus on accurate diagnosis and correct specification, not one-size-fits-all solutions.
Reviewed by Our Waterproofing Surveyor
Michael Young
Technical Manager & Waterproofing SurveyorMichael leads the technical standards and waterproofing expertise at Advanced Damp. He carries out waterproofing and damp surveys across London, specifying tanking and cavity drain systems based on the structure and water risk rather than a default approach, and reviews complex commercial and high-risk projects. Our surveys are carried out by CSSW qualified surveyors and we are members of the Federation of Damp.
Meet the full team →Basement Tanking Across London
We carry out basement tanking from our central London office at 45 Fitzroy Street, covering all London boroughs as well as Essex, Kent, Surrey and the wider South East.
London basements are particularly exposed to damp and water ingress. Rising groundwater, heavy rainfall and deep excavations for new developments have changed how water moves through the ground, and properties in areas such as Fulham, Hammersmith, Chiswick, Wandsworth, Southwark and Walthamstow are among those most affected. Period basements built without a damp proof course are especially vulnerable, which is why correct system selection matters so much in the capital.
See examples of our work in our basement waterproofing case studies.
Frequently Asked Questions
What is the difference between tanking and a cavity drain membrane?
Tanking is a Type A barrier system: a cementitious coating bonded to the structure that physically blocks water. A cavity drain membrane is a Type C system that accepts water may enter and manages it through a drained cavity and pump. Tanking suits sound structures with moderate water ingress; cavity drainage suits higher water pressure and habitable conversions.
How long does basement tanking last?
A correctly specified and installed cementitious tanking system bonded to a sound, stable substrate can last for decades. Failures almost always trace back to poor preparation, the wrong product, structural movement, or water pressure beyond what a barrier system can resist, which is exactly what our survey is designed to rule out. New installations carried out by our team are covered by a written 10-year guarantee.
Can a basement be tanked from the inside?
Yes. Internal tanking is the standard approach for existing basements, since excavating externally is rarely practical. The waterproof slurry is applied to the internal face of the walls and floor after preparation, then finished with appropriate renders and plaster.
Is tanking suitable for Victorian and period basements?
Often, yes, and period properties make up a large share of our London tanking work. Solid brick walls and lime mortar need careful preparation and the right product selection, and in some cases a cavity drain system is the safer choice. The survey determines which approach suits the structure.
How much does basement tanking cost?
As a general guide, a small cellar tank starts around £1,500 to £3,000, a larger basement is commonly £3,000 to £8,000, and a combined tanking and cavity drain system for a habitable conversion can run from £5,000 to £12,000 or more. The exact cost depends on the size of the basement, the condition of the substrate, the preparation needed and the finish required, so we provide a fixed-price quotation following the survey. If you proceed with the works, the survey fee is deducted from the cost.
Can I tank a basement myself?
Cementitious tanking products are sold to the public, and a competent DIYer can tank a small, sound, dry cellar. In practice the result lives or dies on preparation and application: if the substrate is not properly prepared, the slurry is applied too thin, or the wall-to-floor joint is missed, the tanking fails and water finds the weak point. For anything beyond a minor area, an actively damp basement, or a space you intend to live in, professional installation with a guarantee is the safer investment, since remedial work after a failed DIY attempt usually costs more than doing it properly first time.
Related Waterproofing Services
Book a Basement Tanking Survey in London
If you are experiencing damp in your basement or lower-ground property, contact our team for a professional assessment with clear, honest advice on the most suitable waterproofing system.