Choosing the correct membrane for the job.
Do you need a tanking membrane? Rubber membrane?
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Well the choice of waterproof membrane comes down to what actually are you waterproofing and to what degree of protection you need. A waterproof membrane by its very title suggests that you are going to introduce a form of physical barrier to a structure (pitch roof waterproofing or flat roof waterproofing for example) to stop any water breeching the waterproof membrane and thus providing a dry and usable internal space. There are so many choices with waterproofing membrane so the question I am often asked is: "how do I choose the right membrane?" Lets take roofing as an example to begin with. Roofing by its very nature requires a highly robust, durable and often flexible waterproof membrane made out of material which can be heat welded on site minimising the effects of defects, a major concern when jointing any form of waterproof membrane a popular materials would be derivatives or compounds incorporating rubber. With over 1 billion metres installed a year in the United States EDPM roofing membrane still seems to be an extremely popular waterproof membrane choice. Membrane roofing jobs require special expertise and quality installations mean dry internal spaces. Waterproof membrane installers/contractors on low slope or flat roofing applications are regulated in the United Kingdom and for peace of mind it is worth investing in a professional roofing contractor to get the right product for the job at hand.
The specification of choosing the right waterproof membrane can be difficult for your application but one thing you can count on is that like a tanking membrane it needs to be 100% defect free for it to work when its tested. So to design out the risk by choosing the appropriate waterproof membrane for the substrate is critical. EDPM roof membrane applications as mentioned earlier are popular as they can be applied successfully as a flat roof membrane. When tackling such a project you need to have as an installer a product which you know is not going to let you down. Rubber membranes applied to flat areas are flexible and can be welded so that joints are minimal. You will also need to be looking for a product which is hard wearing and can deal with the effects of UV as well. The problems with some roofing membranes especially flat roofing membranes is that they can break down over time due to sunlight and fail or most commonly are just not adequate for the job in which they are specified. Products such as ash felt or liquid applied roof membranes or a single ply membrane need expert preparation to ensure full adhesion. This bond is critical for the success of the waterproof membrane and as such you should take advice from the manufacturer to ensure that you prepare the substrate adequately.
New spray applied polyurethane products which are flexible can be applied over most substrates and because of their application technique are very forgiving and some can be applied with no joints and to a variety of different thicknesses. I have seen this type of waterproof membrane be applied not only in roofing applications (new build or existing) but also a a retrofit application over failed initial attempts. In addition I have seen this technique work in basements and podium decks to protect them from water ingress. These spay applied products need to be applied by professional installers and are more expensive than a DIY alternative from the builders merchants. Ask the professional installer for a guarantee for the application because although this may be an more expensive option at least you will have recourse if there is every a problem in the future.
Nothing changes in relation to the right type of waterproof membrane choice when you look at waterproofing a below ground structure. You need to assess the following criteria to make a informed choice for your project., Questions like " What degree of waterproofing do I need?" are a important starting point. Lets say you have a basement but your only going to be parking you car in there and you don't mind a bit of damp or water penetration. Then you may not need to apply a wall membrane (either internal or external) and you may just go for a water resistant type of concrete. If it leaks through the joints or from anywhere then its not a problem you have accounted for that at the initial design stage. So depending upon what your using the basement space for dictates what waterproof membrane you choose. If you are for instance looking for a dry and habitable cellar, membrane choices will then extend to either an internally applied "tanking" membrane which will hold water back or now we are seeing the use of cavity drain membranes internally applied as a professional waterproofing contractors weapon of choice when going about waterproofing cellars. Just to elaborate the "tanking" waterproof membrane approach means good preparation then depending upon what type of tanking product you are using a membrane being applied to the entire space as a means of holding back the water.
The Cavity Drain membrane is completely different and is a mechanically fixed dimpled membrane which diverts any water that may enter the building fabric to a point where you can discharge it before it reaches important internal finishes. In some projects you may have to use a combination of both tanking and cavity drain to get the right degree of water tightness so I would seek a professional waterproofing contractors advice on this. The choice of waterproof membrane now is vast and can be confusing and although new products are coming into the market the entire time, the principles of successful waterproofing either on a roof or in a basement have not changed nor will they. Water has the ability to find the smallest defect and enter a property leave nothing to chance. Consult a professional installer who can design the risk of water penetration out of the project.
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