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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 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 protect 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 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 a 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 a barrier system, adding fixtures and fittings can also be tricky. Any 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. 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 fitted to the system using the fixings provided, which makes it easy to install electrical outlets or shelving etc. 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
10 Year Guarantee
We pride ourselves on the quality of our work and commitment to customer satisfaction. Our qualified CSSW surveyor will visit your property and carry out a full survey of the basement. Once complete we will send a detailed report with a custom waterproofing design and formal quotation.
The installation is carried out by fully qualified technicians who hold an NVQ Level II Diploma in Structural Waterproofing. Each job is overseen by the Lead Technician and our Project Manager to ensure all works are completed in accordance with BS8102:2009.
On completion of the installation, we will issue you with a 10 year guarantee, which is fully transferable in the event of a sale. 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.
Major Damp Issue in Basement
James Heale, 21st September 2016
Toby Bourne, 5th February 2015
Carolyn Anderson, 6th November 2014
Basement Flat Damp Issue
Juman Kubba, 6th January 2015
Heather Butensky, 2nd April 2015
Elisabeth Lecourt, 24th April 2015
Ruth Douglas, 16th September 2014
Membrane in a new basement
Allan McClune, 16th March 2015
CLAIRE LUKMANJI, 29th June 2014
How a company should be run
Graham Erickson, 21st September 2016
Pam Winkworth, 5th August 2014
Reasons to Choose London Waterproofing Solutions
✓ Over 80 years experience
✓ Member of the PCA
✓ Written guarantees on all work carried out
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