London Waterproofing Solutions Ltd
What causes basements to flood?
The recent increase in heavy rainfall has resulted in a number of basements and cellars flooding, particularly in the London Area. The reason for this is often due to the clay based soil in London, which creates perched water tables. Because the clay prevents groundwater from freely draining away, the water sits against the structure and the resulting hydrostatic pressure will exploit weaknesses leading to flooding.
Basements, by nature of their construction, will almost always be damp. This is because moisture present in the ground penetrates through the walls and floor. Flooding occurs when water in the ground builds up against the structure. An increase in the groundwater level can happen for several reasons including heavy rainfall, location of the property near to water courses, construction of another basement nearby or a burst water main. When flooding occurs you may only see a small amount of water enter, however in many cases several inches of water can enter the basement in a short space of time.
It can be very unnerving when you see water flooding into your basement and you’re not sure as to where it is coming from. The good news is that it can be treated to ensure the problem does not happen again.
Clay based soils present a high risk of a perched water table.
As water percolates into the ground, it doesn’t drain away freely, sitting against the structure.
The resulting hydrostatic pressure exploits weaknesses in the structure, causing the basement to flood.
How do we waterproof your basement?
Whether you want to use your basement for dry storage, or to convert it into another room such as a laundry room or extra bedroom, an appropriately designed waterproofing system should be installed. The waterproofing system should be designed by a CSSW qualified surveyor and you can book a free survey on 020 3794 4200 or by using our contact form.
The code of practice that covers waterproofing of below ground structures, such as basement and cellars, is BS8102:2009. An in-depth explanation of this code of practice can be found here, however the basic requirements for selecting a system should take into consideration the following:
- The proposed use of the basement
- Accessibility for maintenance
- Suitability of the chosen method for the structure
No matter what the environment, or whether there is a history of flooding, the code of practice states that a risk of flooding should be assumed at some point in the life of the structure.
BS8102:2009 gives us two methods for waterproofing an existing basement or cellar as follows:
Type A Barrier System (Tanking)
The Type A method, commonly known as tanking, is the application of a waterproof render or tanking slurry to the walls and floor of the basement. The system is designed to act as a barrier to keep water out. While this may seem like the obvious choice, there are many downsides to using this method as the primary form of waterproofing.
Tanking relies on obtaining a good bond strength to the substrate. With many existing basements and cellars constructed of brick, the preparation required can often mean the use of grit blasting or bush hammering, which can create a lot of dust and debris. If a good bond is not obtained, then the risk of failure is increased especially when the tanking render is subjected to hydrostatic pressure. With brick built structures, there is always a risk of movement which can lead to cracking of render coats and failure.
With a barrier system, adding fixtures and fittings can also be tricky as penetrations through the render could result in flooding or dampness and will invalidate any warranty.
Failed tanking render in a vault.
Type C Cavity Drainage Membrane
The cavity drainage system is the most popular modern method for waterproofing basements and generally considered the industry standard. This involves the installation of a polymer studded membrane to the walls and floor, with drainage channels formed around the perimeter, leading to a sump & pump or existing drainage.
The design of this system manages water entering the basement, so there are no additional stresses induced within the structure from hydrostatic pressure. The membrane can also withstand small movements and vibration without being compromised.
Adding fixtures and fittings to a Type C system is also a lot easier. A dry lined wall can be installed using the special sealed fixings, making it easier to add electrical outlets, shelving and other fixtures. Dedicated fixings can also be provided for heavier items that may need connecting directly to the wall, such as large screen TVs or kitchen units.
Where basements have a low head height, an epoxy resin can be used on the floor slab to create a combined system that offers complete protection in accordance with BS8102:2009.
Because there is little to no preparation of the substrate needed, the cavity drain system can be installed quickly and efficiently, creating less dirt and disruption, leaving you to put your newly created dry basement to good use. Your old basement or coal cellar could soon become your new office, home gym, laundry room, media room or simply a dry storage area.
Cavity drainage system installed to a vault, ready for dry lining.
Cavity drain membrane installed to basement flats
Architects & Developers
When BS8102 was revised in 2009, one of the key additions was the requirement for a CSSW qualified surveyor to be involved with the design team to advise on the waterproofing for any basement construction. We have provided the design and installation for a number of basement waterproofing systems for new build and renovation projects throughout London.
For new build projects, we understand the requirements of warranty providers can be strict when it comes to basement waterproofing, this is due to the higher cost of reinstatement works if something goes wrong. Many warranty providers such as NHBC, LABC and CRL will require two forms of waterproofing. Our CSSW surveyors will be able to advise the best options to use and provide drawings and design advice.
During the construction phase, our surveyor will be on hand to address any queries or potential issues to ensure the waterproofing is not compromised by changes in the design as the works progress. To find out more contact us on 020 3794 4200, or send your enquiry through via email.
The basement waterproofing process
To begin with we will carry out a free survey of your basement to gain an understanding of your requirements and design a suitable waterproofing system. This survey is carried out by a fully qualified CSSW surveyor, who will also be your main point of contact throughout the works. To book a free survey, please call us on 020 3794 4200 or fill in our contact form.
Following the survey, we will provide you with a detailed report which will include a breakdown of the recommended treatment, any specific requirements you have, the process of works and a site plan detailing the different elements of the system. The installation is carried out by our own teams of qualified technicians and all our lead technicians hold an NVQ Level II Diploma in Structural Waterproofing.
Once you have confirmed your booking, you will be assigned an installation team and during the works, the site will be visited at regular intervals by our Project Manager and / or the surveyor. All rubbish generated by our team is removed from site and the work area will be left tidy before we leave. On completion the works will be signed off by the lead technician and the Project Manager or surveyor and on receipt of the final balance, the 10 year guarantee and system manual will be issued.
10 Year Guarantee
On completion of the installation, we will issue you with a 10 year guarantee. Our guarantees are issued for the property making it simple to transfer in the event of a sale. We do not charge for updating guarantee information with a new homeowner.
For a small additional fee, our standard guarantee can be underwritten by Guarantee Protection Insurance for your peace of mind. The cost of the insured guarantee is based on the value of the contract and will be confirmed with your initial quotation.
Customer Testimonials
Reasons to Choose London Waterproofing Solutions
✓ Over 80 years experience
✓ Member of the PCA
✓ Written guarantees on all work carried out
✓ Family run business
✓ All work compliant with BS.8102:2009
✓ Free initial survey by a fully qualified CSSW surveyor
Our promise to you
For your peace of mind we are fully insured and hold the following policies
✓ Public Liability
✓ 10 Years Warranty
✓ Fully qualified CSSW surveyor
✓ 10 year guarantee on installation
✓ We are approved TUG contractors
✓ Full public liability insurance