Why do balconies need to be waterproofed?

Winter, rain and ice are often symptoms of higher infiltration risk that, if not resolved, can cause damage to the building structure over time. Usually, these types of problems arise from worn or poorly installed waterproofing. Below we’ll look at a few solutions used to avoid or resolve these issues in terrace and balcony floors.

It’s raining again. Your shopping, slippery balcony has transformed an average downpour into a long-running nightmare – when it rains, it pools; when it pools, it crumbles, and when it crumbles, the sealant goes to hell and doesn’t even mention the joints. When you first moved in, the condition report wasn’t too bad – a chip here, a crack there, small stuff. And today? Leaking balcony tiles. Mould, decay and the sickening stench of inner damp lingers despite your best efforts. Your balcony waterproofing membrane is virtually non-existent.

The good news? Some balcony waterproofing can save you grief, money and damage caused by leaks. But what do you look for? Where do you start? Megasealed have you covered.

Balcony leaks are common, particularly in older homes, and if left unchecked can lead to extensive damage. It’s worth remembering too that termites are attracted to damp areas, and fungal growth around the home and a termite infestation is one headache you don’t need. If your balcony is leaking, it is important to take steps to rectify the problem before it causes wider issues. Balcony waterproofing doesn’t have to involve major renovations; with a balcony sealant you can have a tight water balcony within a day and at a much lower cost than taking up the tiles, replacing the waterproof membrane…or paying thousands to rectify termite damage in the future.

Check out Hitch Property Constructions for a wide range of balcony repairs.

Why do balconies leak?

The failure of the waterproofing system could be attributed to the fault of an inexperienced contractor; however, in most cases, the common contributing factors to failures of balconies can be attributed to:

  • Lack of planning prior to construction
  • Incorrect substrate and use of substrate materials
  • The substrate is not sound and solid (allows for too much movement)
  • The substrate is not cleaned and made ready to accept the membrane (dust, uneven surfaces, rough joins – membrane won’t adhere) 
  • Incorrect membrane selection (use of indoor membrane instead of the outdoor membrane)
  • Minimal amount of drain outlets and the few that are installed are too small in diameter
  • Incorrect or insufficient fall to the drainage outlet
  • No overflow provisions provided
  • Lack of detail around waste and other penetrations
  • Inadequate flashing or waterproofing to the balcony floor and external wall join or to the treatment at the window door opening

By ensuring that some thought has gone into the preparation and design of the balcony and the waterproofing system to be used can save time and expense in the future to rectify a leak.

Many balconies are being constructed with minimal falls to the substrate, especially in multi-level apartments. A balcony with minimal fall is susceptible to water pooling and moisture between the membrane and tiles, known as “ponding”. If the waterproofing membrane applied cannot withstand ponding water, over time the membrane will break down, causing water leaks. Waterlogging can also cause joint failure, leading to leaks.


Other factors to consider

Other contributing factors can cause the waterproofing system to fail.

The type of tiles to be installed. Tile is subject to UV, dark coloured tiles soak up heat from the sun, which will transmit the heat into the membrane and substrate, causing movement to all the materials. Each material will move differently and could cause the membrane to tear. Once the membrane has torn penetration of any water can then seep under then membrane.

The installation of expansion joints to the tiles is very important to allow for the expansion and contraction of the tile. Lack of expansion joints can cause tiles lift due to compression and upheaving, thus tearing at the membrane allowing water migration into the room or apartment below.

Maintenance also plays an important part in ensuring any water falling on the balcony flows to the drainage outlets.

Blocked floor wastes or outlet drains, can cause pooling or ponding of water which can enter the building via the openings or above any flashing level.

Checking joints in the tiles to ensure they are still grouted and debris has not been ground into the join, causing the membrane to be penetrated.


Australians love their renovation projects. We’re certainly a resourceful lot. While the Megasealed team embraces the DIY philosophy, there are some projects that shouldn’t be attempted lightly – one of them being, waterproofing your balcony floor. One small mistake may not seem like a big deal now, but waterproofing issues don’t crop up straight away and are often invisible to the untrained eye. A trained Megasealed technician will apply the latest balcony waterproofing products to ensure stringent balcony waterproofing standards are met from day dot. Meaning? You save coin in the long-run.

Spotting The Slip-up

Too often, builders neglect basic waterproofing standards, cut corners and therefore, their work is inherently flawed. With this said, balcony damage is probably not your fault – especially if you’re renting. Homeowners may have inherited an already problematic balcony from the moment they signed the dotted line. When a builder slaps together a house or contributes to an apartment, they sometimes build the balcony first and place the door afterwards, installing the membrane as the last step. This is a serious floor/wall junction problem. Australian standards are supposed to stop this from happening, but a lack of design detail means the builder will fall back on old, incorrect practices. It’s not malicious, and they don’t know any better.

What’s Your Angle?

While we’re down on the floor, take a look at your balcony – does it gently slope toward a central drain? Are the water barriers and grouting in good condition? If you answered no twice, you’re in trouble. If a balcony isn’t draining properly, an extensive re-tile may be worth considering – sure, it’s expensive, but water ingress isn’t like a seasonal virus, it won’t pick up and leave once the rain stops.

Don’t Hold Back

A waterproofing membrane is essential to keeping your outdoor area in prime condition – think of it as a raincoat for your balcony. You don’t like being wet, you hate damp clothes, and the smell of mildew doesn’t scream homely and comfortable, so tackling balcony leaks as soon as possible will make your days (and nights) a whole lot sweeter. Contacting Megasealed and taking advantage of our wide range of balcony waterproofing solutions will soon put a smile on your face – our services are lighter on the wallet in the long term and come loaded with insider knowledge to help you maintain your freshly sealed balcony.

What to consider before waterproofing

In new construction, the designer decides the best waterproofing solution for outdoor flooring. A Best Practice which has become commonplace is that of applying a drainage membrane on the underside of the substrate, serving as support for correct waterproofing. UNI11493-1 regulations, in fact, state that “the indication of a drainage and protection membrane, applied between the substrate and water barrier, is a measure with the objective of preventing water stagnation from penetrating the structure.”

On the other hand, in renovations, it’s important to evaluate different factors in order to choose the best solution based on certain basic conditions.

In this case, the first thing to analyze is the area where the intervention will take place:

  • evaluate the state of conservation of the flooring and substrate
  • verify the layered section of the structure
  • make sure that the slope of the flooring is appropriate
  • check that there are no fractures or separation between the various layers

Depending on the conditions of the terrace or balcony in question, you can choose the best solution between those described below.

Choose the most suitable waterproofing solution for renovations.

Based on the conditions of the terrace or balcony, you can choose the best solution by evaluating several factors. If the flooring is in perfect shape, it might be enough to directly waterproof the floor covering.

However, if there are issues with the tile, such as cracks or holes, it’s a good idea to remove them and waterproof the underlying layer, that is, the substrate. If the condition of the substrate is also inadequate, the best solution is then to waterproof the layer beneath the substrate, hence preventing any possible future infiltrations.

Waterproofing solutions without removing the tile

If the flooring is in good condition, without cracks or tenting, liquid waterproofing is a good solution to employ without having to remove the tiled surface. It is easy to use and can be applied quickly with rollers or brushes onto the entire surface without leaving gaps while creating a thickness of only a few millimetres. Such procedure, which should be carried out by carefully following the instructions indicated by liquid membrane manufacturers, is resistant to temperature changes, bad weather, chemical substances or stagnant water. A fundamental aspect to consider with the supplier is the suitability of the product the existing flooring.   

Looking for balcony repairs Melbourne? Look no further. Hitch Property Constructions has you covered.

Waterproofing solutions between tile and substrate

If the flooring is damaged or unsuitable, it is necessary to remove it and intervene in the layer underneath completely, that is, on top of the substrate. Two main solutions stand out from what’s available on the market: waterproofing membrane rolls or waterproofing liquids.

Rolled membrane waterproofing systems

On the market, there are numerous solutions in which to use rolled membranes to waterproof the substrate. The most common are bituminous, rolled, self-adhesive waterproofing membranes, that can be applied with hot air welding on site.

The substrate must be clean, dry and free of dust and debris. Subsequent to the application of the adhesive membranes, thinset can be spread for the tile application.

If the waterproof layer under the substrate is undamaged, you can implement a cleaner and faster solution, such as a polyethylene rolled membrane. In order to use this type of waterproofing, we suggest using Floortec, a membrane composed of a base in polyethylene laminated with non-woven fabric on the underside. With a total thickness of only 3 mm, Floortec not only reinforces the waterproofness of the substrate without substantially influencing the interior of the flooring, but it also compensates structural tension, manages moisture which rises through the installation and provides additional load resistance. Upon the installation of the membrane with cement adhesive, the tiles can be installed.

The cement-based liquid compound waterproofing system

An alternative to a bituminous membrane may be the application of a cement-based liquid layer that is easy to apply on top of the substrate. The product is a cement-based mixture to which polymers and other elements impervious to water are added. The tiles can then be applied over this layer with the appropriate tile adhesive. This procedure is simpler than the previous one. Still, the cement layer, in practice, is not perfectly waterproof and could dilate or shrink as a result of temperature changes, allowing a small amount of humidity to pass to the layer underneath. This technique is recommended in interventions where there is no doubt that the substrate is in perfect condition and does not present cracks or hairline fissures.

Waterproofing solutions under the substrate

The best solution to solve and prevent any infiltration and subsequent degradation is to intervene under the substrate. For optimal results, the procedure should include the application of a waterproofing layer, on top of which is applied a drainage membrane that provides protection and allows the outflow of water that percolates from the upper layer of the draining substrate, as suggested by regulation UNI11493-1.

The bituminous membrane waterproofing system

Bituminous membranes are the most popular system used to waterproof under the substrate of terraces and balconies. These membranes are derived from the distillation of crude oil and commercially sold in prefabricated rolls. In the thickness of the roll, there is also an armature (in glass-fibre or polyester-fibre) to increase resistance. In pedestrian areas, such as terraces and balconies, the application of a bituminous membrane with a thickness of 4 mm is recommended, in order to increase the mechanical resistance and maintain the elongation property that is characteristic of this material. The sheets of prefabricated rolls are easy to install and, due to flame bonding, guarantee complete adherence.

In application settings where an open flame is not permitted, the same membranes are available with an adhesive layer. These are easier to apply, yet provide slightly reduced effectiveness.

The importance of draining membranes

Draining membranes under the substrate are true lifesavers for the structure of the building.

The main cause for damage to terraces and balconies is, in fact, the presence of water when it inevitably infiltrates to the interior of the substrate and slowly wears the various waterproofing layers. The unique structure of the drainage membrane prevents this type of problem. For this reason, we recommend Draintec 8, a membrane designed by our technicians to allow water drainage through a series of drainage channels, compensating hydrostatic tension in contact with the substrate and the bitumen-based membrane. Its particular shape supports and decreases load compression resulting from pedestrian or load passage. With a thickness of only 8 mm, Draintec 8 contains two glued layers. The first is a base in polyethylene with cone-shaped elements used to separate and drain liquids. The second layer is in non-woven fabric which is laminated above the base, with the function of blocking the passage of small particles and debris so that these do not obstruct the channels and decrease the effectiveness of the membrane.

When using a draining substrate, we suggest installing Draintec 8S, composed of a net with a looser weaving structure than that of Draintec 8.

Using a perimeter profile for optimal results

To complete an intervention with state-of-the-art results, we suggest installing the Border Tex BD profile along the perimeter of the terrace or balcony. The purpose of this edge profile is to guarantee the complete drainage of water through specifically designed drainage holes. Bordertec BD should be positioned under the substrate, precisely between the drainage membrane and the bituminous membrane. Together with the Draintec 8 drainage membrane, it is the ideal product to protect the terrace structure from infiltration and deterioration.

Hitch Property Constructions has a wide range of the Melbourne balcony repairs right here. 

Standards for Building Work in Australia relating to waterproofing

There are national standards relating to the materials and practices of making sure a balcony is waterproofed. Any external balcony needs to meet these standards to provide adequate protection-

  • Materials AS4654.1-2012
  • Design Installation AS 4654.2-2012

Once a home is given the Occupancy Permit or Certificate of Final Inspection, then the builder can still be held liable for another ten years for failed waterproofing on a balcony. In the case that a Certificate or Permit was never issued, then the liability can run for an even longer period. Even if the builder uses a certified subcontractor and receives a certificate from them, then that does not means the builder has no liability. They are responsible for the overall building work as the main contractor.

Builders are advised to look at the details of the NCC and Australian Standards AS4654 AS 4654 Parts 1 and 2 to familiarize themselves with the requirements and ensure that they are adequately waterproof the balconies on their building work.

The builder needs to understand the methodology of how waterproofing is applied and how to prepare the substrate and prepare the building itself to receive the waterproofing. Builders and certainly waterproofers do have to understand movement and the control of movement in buildings.

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