Basement Tanking simplified means keeping water out of your basement or below ground structure. Your basement does not need to be fully underground either to have potential problems with water. Even sloping sites where your basement is built into a hill side or has just one wall with earth up against it means that you could have a problem with water in the future. So what are your Basement Tanking Options.?
Simplified there are two ways of tanking a basement. The first method is to use an external system. These systems when applied to the outside of the structure form a barrier to stop water penetrating the building. To use this approach you can only really do this when constructing a new basement. (for the obvious reasons). The area to pay close attention to is the wall floor junction. Successful external basement tanking means forming a waterproof membrane barrier both underneath the concrete slab and up the vertical surfaces effectively making a waterproof tank around your basement. This has benefits of keeping the building dry and using the power of any water present to push the membrane onto the structure. Many designers use a land drain at adjacent externally to the wall floor junction footing. This is where water pressure is at its greatest and the land drain intercepts water and diverts it away from the applied membrane and the structure. There are a variety of different products available to people using this choice when basement tanking including, paint on or spray applied liquid membranes, torch on/heat welded membranes, bonded sheet membranes, clay matting membranes etc. Please be aware that although it may seem easy in principle the detailing and site conditions can be a significant problem in getting these systems put in properly. It only takes one error in workmanship in applying external basement tanking products and you could have a really waterproofing disaster. Wet, muddy and also very cold conditions may not suit the manufacturers recommendations when applying this type of system be very aware that unless you follow their guidelines you may have no recourse should things go wrong.
We can also achieve success in basement tanking by using an internal basement tanking alternative. This is traditionally used on all existing basements and can also come in a variety of different products. The secret here is making sure the surface preparation is correct to receive the type of basement tanking product you wish to apply. So depending upon which product and what substrate you are applying it to you could spend many an long hour, using a bush hammer to scabble the bricks, racking out the mortar joints, sand blasting or needle gunning the bricks to get the right "key" for your basement tanking solution to work. Techniques applied externally can also work internally, slurry trowel applied systems, paint on bitumen, asphalt based products, etc the problem being that if water pressure is applied your basement tanking it will be trying to "push it off" the walls. This puts extreme pressure on the applied system and can cause defects meaning water can come in. Also be very aware here of drying out times and fixtures and fittings applied to your basement in the future. These type of systems need to be defect free and cannot be punctured without risking a compromise of the system. Be aware also that these type of systems are very difficult to get on but they are indeed very difficult to remove. When dealing with listed buildings throughout the entire UK you will need to be using a basement tanking system which is removable at all times. These applied systems are definitely not and will not conform to conservation requirements.
The other way we can look at the basement tanking problem is to use what is known as a water management system. Internally! Yes, these systems are known as cavity drain membrane systems and are successfully being specified and installed into thousands of new build and refurbishment basement projects and have been for over 30 years. Suitable for domestic and commercial environments this internal drained cavity systems is a basement tanking technique which is not in any way holding water back but diverting it to spaces created by the system to eventually remove it via natural gravity drainage, existing drainage or a sump and pump. These systems require a minimal surface preparation unlike the other basement tanking options making them quick and easy to install with no messy, noisy and expensive preparation works. They are a series of cavity drain membrane dimpled HDPE rolls of inline studded dimples which form an air void on the retaining walls. These basement membranes create a air gap so if water is to get through the structure it can be guided to an exit point. Some of these dimpled sheets can accept direct render finishes. This type of basement "tanking" is taking over from traditional forms for wet applied systems by professional waterproofing contractors as they conform to all the British standards as a very effective way of basement waterproofing. Professional Waterproofing contractors should always be instructed to apply and guarantee the system whatever you choose. Basement tanking is not a job you want to do twice. Get it right the first time and follow the experts advice.
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