What is cementitious tanking?

Will Cement Tanking a Cellar Keep Moisture Out?

A basement or cellar space can be very susceptible to damp. This is because moisture can get in through the walls from the ground, and since the basement is below ground level, there is often much more moisture around the external walls from the soil, especially in wet weather. This is why if you have a cellar in your home that has not been damp-proofed, you might notice that things inside the cellar are affected by damp and mould after a while, or the walls in the basement are moist even if you do not have any damp problems in the rest of your home. If you want to be able to use your cellar for more storage or are considering converting it into a liveable area of your home, then cement tanking your cellar can be an ideal way to keep moisture out and prevent any further damp problems.

What is Cementitious Tanking and How Does It Work?

If you are thinking about converting your basement so that you can use it for storage without worrying about damp affecting your belongings or you want to take advantage of the space to use it as a second living room, bedroom, or another room in your home, then protecting it from damp and flooding is one of the most important first steps to take. Even a small damp problem in the cellar can cause issues by damaging your belongings and making the area unpleasant to spend time in. In addition to this, damp problems in your basement or cellar can get much worse as time goes on, leading to structural damage of your property and even negatively impacting the health of yourself and your family. Cement tanking involves applying a waterproof slurry to the basement walls and floors, to prevent moisture from getting through.

What is the Difference Between Waterproofing and Tanking?

When damp proofing a basement there are two main options to consider. These are tanking and waterproof membranes. While both work the same way, there are some considerable differences between the two.

Cementitious Tanking and Damp Proofing

Tanking the basement for damp proofing involves coating the walls, floor, and sometimes the ceiling of the basement with a waterproof slurry to seal it. The material is usually cement-based and is designed to prevent any moisture from entering at all. However, it can be a lot of work depending on the age and state of your basement currently. If you need to waterproof a basement that has been renovated in the past, then you will need to ensure that all plaster and other wall coverings are completely removed before the cement tanking slurry can be applied. You will also need to make any necessary repairs such as repointing, and in some cases, coat the masonry with a salt-neutralising product to ensure that the walls are at peak structural integrity, as this will make sure that the tanking slurry can work as effectively as possible once it has been applied and dried.

What is Cementitious Tanking Slurry?

Applying a cement tanking slurry is usually the best way to deal with low-level cellar and basement damp problems. It can be used on the entirety of the basement walls and floor or used to patch problem areas that may be more prone to damp than others. You can also use cement tanking alongside other damp proofing products such as a cavity membrane drainage system for extra protection. The tanking slurry is applied directly onto the masonry substrate of the walls to create a waterproof barrier that water is not able to penetrate. Once it has dried, you can apply internal finishes such as plaster and paint or wallpaper to finish your habitable area in the cellar.

Cavity Membrane Systems

You can use a cavity membrane system for damp proofing your cellar either together with or instead of cement tanking slurry. This involves installing a high-density studded plastic membrane, which is fitted to the walls and floor of the cellar. It is designed to prevent the water from entering the basement. Instead, there is a cavity left behind the membrane where the water becomes trapped before it is drained down into the floor cavity and away from the basement, often with the help of modular drainage pipes and a sump pump, which may be necessary if there is no natural drainage system present. This type of waterproofing for a cellar is an ideal choice if the area is prone to getting a lot of damp problems or flooding. It can be used on its own or you can apply a cement tanking slurry first before adding the membrane for additional protection against any moisture that might find its way through. It is designed to handle larger amounts of water in comparison to tanking.

Preparation for Cementitious Tanking and Damp Proofing in London

Successfully applying a cement tanking slurry to waterproof your basement will require a lot of preparation. Unlike a cavity membrane drainage system, which can be installed on existing walls and floors, you will need to fully remove any previous coatings on the walls. This includes taking off any existing render, plaster, paper, or paint from the walls and restoring them to the original masonry. Only when this has been done and any necessary repairs have been made can the slurry then be applied to the walls. Applying slurry over existing wall coatings, or onto masonry that has not been suitably repaired, can render it less effective. If you are tanking a cellar, another key part of the preparation process will also involve forming a cove joint in the floor slabs.

Once the prep work has been done, you may find that a key is needed for the slurry to properly bond with the substrate. If your cellar has materials such as waterproof concrete, for example, then this might be a challenge. Before applying the slurry to the masonry substrate, you can improve your results by first applying a bonding slurry coat over the substrate, which is designed to provide a key for the tanking slurry to bond to once applied.

What are the Main Benefits of Using Cementitious Tanking Slurry?

If you have a basement or cellar in your home, then you will need to damp proof it correctly before it can be anything but unused extra space. Without damp proofing, you will struggle to even use your basement as a storage area since anything that you put down into the cellar will be quickly impacted by the high levels of moisture and damp. Because of this, it’s no surprise that there are many benefits of using a cementitious tanking slurry to update your basement.

Easy to Apply

While there’s a lot of preparation involved for some cellars, the good news is that a cementitious tanking slurry is usually an easy product to apply. You may even be able to do it yourself once the basement has been prepared. And if your basement walls are still the original masonry substrate and do not have any other coverings, then all you may need to do is some minor repairs and apply a bonding coat before brushing or rolling the slurry on.

Liveable Space in the Basement

Whether you need more storage space or want to create a new room in your home, damp proofing is the first step to converting your basement into anything but a dark and damp area. Applying a cement slurry will provide a sealant for the walls and floors that allow you to use your basement for storage without worrying about water damage. In addition, you have also now finished the first main step towards converting your basement into a liveable room. Once it’s been damp proofed, you can add things like flooring, wall coverings, and have an electrician install power sockets and lighting.

Protection From Structural Damage

By using a cement waterproofing slurry to damp proof your basement, you can protect your home from the structural damage that can often be caused by damp that has been allowed to go on for too long. After a while, damp can lead to serious issues in the home such as wet rot and mould issues that could even make your home unsafe if not repaired.

Save and Make Money

Once your basement has been damp proofed with a cement slurry, you have a much more usable space, which in turn can add to the value of your home, helping you get more for it in the future if you decide to sell. Along with this, damp proofing the basement also prevents cold air from getting in and seals the basement so that warm air can’t escape, ultimately helping you save on your monthly energy bills. And, a damp-proofed, liveable basement could even be a source of income. People are often willing to pay for storage space, or you could rent it out as a spare room or even a whole apartment depending on the size.

If you want to keep moisture out of your basement and avoid damp problems, then applying cement tanking is a good option to consider.

Equipment Used During Our Surveys

Professional Moisture Meter

Equipment Used During Our Surveys

Purpose:

Takes comparative moisture readings from walls, ceilings, floors and timber to identify abnormal moisture patterns.

Common Uses / Notes:

Used when investigating rising damp, penetrating damp, condensation and leaks. Readings support the survey but are not a diagnosis on their own.

Subsurface Moisture Meter

Subsurface Moisture Meter

Purpose:

Detects moisture beneath the surface of suitable building materials.

Common Uses / Notes:

Helps determine whether moisture is confined to surface finishes or extends into the building fabric.

Non-Damaging Moisture Scanner

Non-Damaging Moisture Scanner

Purpose:

Scans surfaces for hidden moisture without causing damage.

Common Uses / Notes:

Ideal for decorated walls, ceilings and flooring where pin testing would be undesirable.

High-Resolution Borescope Camera

High-Resolution Borescope Camera

Purpose:

Inspects hidden or difficult-to-access areas without opening up large sections of the building.

Common Uses / Notes:

Used beneath floors, inside cavities, behind walls and around pipework to identify damp, leaks, decay and concealed defects.

4K Aerial Inspection Drone

4K Aerial Inspection Drone

Purpose:

Captures high-resolution images of roofs and other inaccessible external areas.

Common Uses / Notes:

Inspects roof coverings, chimneys, flashing, gutters, valleys, parapets and high-level masonry. Subject to weather, safety requirements and flight regulations.

Atmospheric Humidity Sensor

Atmospheric Humidity Sensor

Purpose:

Measures indoor relative humidity levels.

Common Uses / Notes:

Helps assess condensation and mould risk alongside temperature, ventilation, heating patterns and room usage.

Gas Detection Monitor

Gas Detection Monitor

Purpose:

Screens for certain airborne gases where unusual odours are present.

Common Uses / Notes:

May detect gases associated with drainage, combustion or flammable substances. Does not replace inspection by a Gas Safe registered engineer where gas appliances or pipework are involved.

Thermal Imaging System

Thermal Imaging System

Purpose:

Identifies temperature differences across building surfaces.

Common Uses / Notes:

Helps locate cold spots, thermal bridging, insulation defects and areas associated with concealed moisture. Results always require further investigation to confirm the cause.

Basic Socket and RCD Tester

Basic Socket and RCD Tester

Purpose:

Performs limited electrical checks during comprehensive surveys.

Common Uses / Notes:

Can identify basic socket wiring issues, AC voltage and RCD operation. It is not an Electrical Installation Condition Report (EICR).

Chemical Vapour Testing Device

Chemical Vapour Testing Device

Purpose:

Screens for airborne volatile organic compounds (VOCs) and formaldehyde.

Common Uses / Notes:

Used where chemical odours, emissions from materials or indoor air-quality concerns are suspected after leaks or refurbishment.

Fine Air Particle Counter

Fine Air Particle Counter

Purpose:

Measures airborne particulate matter (PM1.0, PM2.5 and PM10)

Common Uses / Notes:

Assists with investigations involving dust, smoke, mould concerns, post-construction contamination and indoor air quality following water damage.

Extraction and Air-Movement Tester

Extraction and Air-Movement Tester

Purpose:

Measures the performance of extractor fans and mechanical ventilation systems.

Common Uses / Notes:

Used in kitchens, bathrooms and utility rooms to identify poor ventilation that may contribute to condensation and mould growth.

Survey Levels and Equipment Provided

Level 1

Basic Moisture Survey

Standard price: £299 + VAT

Special offer: £199 + VAT until the end of this month

The Level 1 survey provides a basic assessment of the main accessible internal surfaces. It is most appropriate for simple, localised damp concerns where advanced testing is not required.

Equipment Included

  • Professional damp meter

Survey Checks

  • Accessible walls
  • Accessible floors
  • Ceilings
  • Visible plumbing and drainage leak inspection
  • Damp-control and prevention information

Suitable For

This survey is suitable for a customer who has found an isolated damp patch, suspects rising damp in a limited area or wants a straightforward check of the property’s accessible surfaces.
Only a standard damp meter is included. Customers requiring deep moisture detection, timber inspection, thermal imaging or roof inspection should select a higher survey level.

The survey fee will be deducted if we carry out the recommended work.

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Level 2

Damp, Moisture and Timber Survey

Standard price: £399 + VAT

Special offer: £299 + VAT until the end of this month

Level 2 includes everything in the Level 1 inspection and adds deeper moisture detection, non-invasive scanning and timber assessment.

Equipment Included

  • Professional damp meter
  • Deep-reading moisture meter
  • Non-invasive moisture scanner

Survey Checks

  • Accessible walls, floors and ceilings
  • Visible plumbing and drainage leak checks
  • Subsurface moisture readings
  • Non-invasive scanning of appropriate materials
  • Accessible underfloor and subfloor checks
  • Wet rot inspection
  • Dry rot inspection
  • Woodworm inspection
  • Damp prevention information

Suitable For

This level is intended for customers who require a more detailed inspection of dampness and timber condition. It is appropriate when moisture may be concealed within building materials or beneath accessible flooring.

The survey may identify evidence of timber decay or wood-boring insects and assess moisture in locations that cannot be properly examined with a surface meter alone.
Level 2 is particularly useful for homebuyers and sellers who want more information about damp and timber before completing a transaction.

The amount paid for the survey will be deducted from repairs undertaken by us.

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Specialist Survey Add-On Services

For complex damp investigations, we offer three specialised laboratory and environmental testing add-ons:

Add-On Service 1

Laboratory Analysis of Plaster Samples

Price £299 + VAT

Description: Small plaster samples are extracted from affected masonry walls and submitted to an independent testing laboratory. The lab analyses the sample for hygroscopic salts (specifically nitrates and chlorides).

Value: Scientifically differentiates true rising damp (which deposits ground salts over time) from surface condensation or lateral penetrating damp. Ensures that remedial recommendations are based on chemical analysis rather than surface meter readings alone.

This service can be beneficial when:

  • The cause of low-level dampness is disputed.
  • Moisture-meter readings are inconsistent.
  • A property has undergone previous damp-proofing.
  • Old plaster continues to attract moisture.
  • Independent laboratory evidence is required.
  • Several possible moisture sources are present.

Note: Salt analysis is only one part of the investigation. Results must be assessed alongside the location of moisture, condition of the masonry, external ground levels, damp-proof course and potential plumbing or rainwater defects. Requires minor invasive plaster sampling (the only add-on requiring material removal). Survey fee credited when repairs are completed by us.

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Add-On Service 2

Mould Identification & qPCR DNA Testing

Price £299 + VAT

Description:  Surface swab samples are collected and sent to an accredited laboratory for advanced qPCR DNA analysis. Identifies exact mould species, measures spore concentrations and detects hidden fungal growth behind furniture, within void spaces, or under floorboards.

Value: Provides precise scientific data regarding mould toxicity and contamination levels, helping establish the exact scale of cleaning, drying and structural remediation needed.

Laboratory mould testing may be useful when:

  • There is an unexplained musty odour.
  • Visible mould repeatedly returns.
  • Water damage occurred previously.
  • Mould is suspected behind cupboards or furniture.
  • Contamination may be present in a concealed location.
  • The visible extent of growth is uncertain.
  • Independent results are needed.
  • Remediation work is being planned.

Note: The results can provide a clearer indication of whether contamination appears minor, concentrated or potentially widespread. This information may be used when deciding the scale of cleaning, removal, drying or remedial work required. Testing should be combined with an investigation of the moisture source. Removing visible mould without resolving the underlying condensation, leak or ventilation problem may allow it to return. Survey fee credited against subsequent remediation works completed by us.

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Air Quality, Gas, Vapour & Airborne Particle Screening
Add-On Service 3

Air Quality, Gas, Vapour & Airborne Particle Screening

Price £299 + VAT

Description:  Comprehensive environmental air testing including:

  • Indoor environmental quality – IAQ
  • Volatile organic compounds – VOC and TVOC
  • Formaldehyde – HCHO
  • Fine airborne particles – PM1.0, PM2.5 and PM10
  • Dust and smoke particles
  • Sewer gases – H2S, NH3 and CH4
  • Flammable gases – CH4 and C3H8
  • Carbon monoxide – CO
  • Hydrogen sulphide – H2S
  • Ammonia – NH3
  • Oxygen measurement – O2
  • Ventilation and stale-air assessment
  • Drain-smell investigation
  • Chemical-odour investigation
  • Air checks following a leak or flood
  • Combustion-related screening
  • Building-material off-gassing assessment
  • General airborne pollutant monitoring

Value: Pinpoints invisible airborne hazards, toxic sewer gases, chemical off-gassing and foul odours resulting from damp or trapped water.

This service can assist when investigating:


  • Persistent foul smells
  • Suspected sewer or drain odours
  • Chemical smells
  • Stale indoor air
  • Odours following water damage
  • Possible stagnant water
  • Building material emissions
  • Fine dust after construction work
  • Poorly ventilated rooms

Note: Unpleasant odours can have several possible sources. Measurements for specific gases, compounds and particles may help identify which source requires further investigation. The assessment is a screening service and does not replace specialist gas-safety, environmental or medical testing where this is necessary. Survey fee credited against subsequent repair works completed by us.

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If you have some questions, please complete this form:

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If you are ready to book a survey and pay, please complete this form:

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