Let’s start with explaining what a waterproofing membrane is. It is a continuous layer of thin, water-tight material laid over a surface. This, for example, would be done on a flat balcony. It could also be done above the structural slab and then again below the finish tiles. By doing this, you are providing excellent protection to the structural slab and the steel therein.
In the case of the tiled area, it must be remembered that the tiles and the membrane should be laid over a sloping level of the screen. This ensures that water flows away from the building into drainage areas. The preparation of this slope is really important, and it is best to test the slope before tiling. Spray the area liberally with water. If any water pools, then there is a problem with the screed angles and levels. Pooled water will seep into a slab over time. This because the general waterproofing membranes work by repelling water as the water moves over them. They are not all specialised swimming pool waterproofing membranes. Swimming pool waterproofing is a whole other ball game.
The waterproofing membranes we are discussing are composed of thin layers of waterproof material, 2 to 4mm thick. There are sheet membranes, i.e. they are supplied in a premade layer, and there are liquid applications. The liquid applications become a layer after application.
The characteristics you look for in a membrane are flexible (very important), strength (flexibility forms part of this measurement), tear-resistance and stretch (cover cracks and move with the flexibility). A specification that is important for outdoor membranes is UV stability.
Sheet-Based Waterproofing Membranes
These are purchased in roll format, then unfurled on-site and laid onto the surface to be treated. A bituminous waterproofing membrane is highly favoured by contractors. Bitumen is sometimes called asphalt. You will recognise it by its sticky, black and highly viscous nature. It is a liquid or semi-solid form of petroleum
The two main types are:
Torch applied bituminous membrane – this is applied with bitumen that is blowtorched on, i.e. it is heated, slightly melts and then pressed onto the surface, and it bonds with the surface as it cools.
The edges of membranes lying next to each other are overlapped by about 100mm and are sealed with the same hot adhesive method. Joint points in any waterproofing system is a point of potential weakness. They, therefore, should be done very, very carefully and thoroughly.
Self-adhesive bituminous membrane – These are covered by a release liner, which is removed during application. No torching is required, it is safer and faster to install, and excellent adhesion is achieved even at low temperatures.
The overlapping of edges also occurs with this product.
There are also PVC waterproofing membranes and composite waterproofing membranes. The composite options have a fabric base that gives good strength and tear-resistance. There is a chemical coating on the fabric which provides water resistance. They are not as flexible as bituminous solutions. These membranes are also factory-produced so are consistent in quality.
Liquid Applied Waterproofing Membranes
As the name implies, this solution arrives on-site in liquid form. It is then either sprayed or brush-applied onto the area to be treated. The curing of the liquid occurs with air exposure, and it forms a seamless, joint-free membrane. By applying more of the liquid chemical per unit area, the thickness of the end result can be adjusted to the needs of the site engineer.
Even though this product is very quick to apply, there will be instances where a very large area will need to be serviced on successive days. This results in “cold joints,” i.e. where the application ends. This is not a problem as overlapping of the new membrane can be done over the old. The product is attracted to itself and will tackily stick to the previous layer.
A liquid applied waterproofing membrane is considered to be superior to sheet-based membranes. The primary reason is they are joint-free. This is obviously subject to the care taken in the application. Too thin and you can expect a leak as breakage and tearing can happen. The substrate to which the liquid is being applied must be suitably prepared to ensure maximum adhesion.
If, after a waterproofing membrane is laid, a concrete screed is often applied. The membrane can be roughened whilst wet by hand “sowing” a thin layer of sand over it.
Contemporary rubber options are very interesting: There are systems that UV protective coatings that instantly block all UV from your roof’s surface. This extends the service life to sound roofs while reducing maintenance needs. A cool roof coating accommodates roof surface temperature drops as much as 10°C or more. It can also reduce cooling needs in the interior and reduces maintenance from damages from thermal stress. Roof repairs last longer by sealing them with an elastomeric rubber roof coating.
Now, To Choose A Waterproofing Membrane
Check for specification properties:
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UV Stability – ascertain if the UV level is high enough for Australia.
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Elongation – basically stretchability, measured in percentages. Look for a minimum of 150%. 200% is a better goal.
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Breathability – ironically the disadvantage of good waterproofing is that when water does find the tiniest entry point into the structure, the water is trapped inside the structure. There are breathable membranes available. They help release water to the air (water vapour). This can only be selected if appropriate for the particle area.
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Tear Resistance – Whilst many membranes have good elongation. This does not equate to tear resistance. Be sure to test it yourself by physically pulling a sample.
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Abrasion Resistance – Wear and tear. Can it resist having something applied to it with people (read “builders”) working on it?
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Chemical stability – enquire about the chemical relationship with its environment in the building. Outside basement walls, for example, are exposed to the soil and rainwater outside.
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Food Safety – concrete water tanks need waterproofing membranes applied to them. The membrane must be food-safe as the water is in contact with the membrane.
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Geometry – With a complicated shape (junction of a column and beam) a liquid waterproofing membrane is preferable. A sheet membrane would form folds etc.
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Case Studies – ask for case studies where the membrane has been used. Ideally, the owners should have experience with the product with a minimum of 8 years.
If these have not answered your questions, please contact us today contact page. We are here to guide you to the best solution with our world-class knowledge. Alternatively, call us [insert phone number] or email us [insert email address] and we will help you protect your property.
