Evading Efflorescence in Tiling
One of the most common member enquiries we receive in the Building Services section nationally relates to problems with tiled balconies and the occurrence of efflorescence.
Efflorescence (as commonly described in the construction industry) is the formation of calcium carbonate on an external surface, in this instance on the exposed face of the tile. Most commonly, the formation of efflorescence is caused by water leaking through cement mixtures and dissolving calcium hydroxide. On contact with the atmosphere the calcium hydroxide reacts with carbon dioxide to form calcium carbonate. In most instances the efflorescence forms around the grout lines.
A more serious problem is leaching. This is where there is serious water leakage in the tiling system and a more extensive build up of calcium carbonate occurs, again around the grout lines and edges of the balcony. Quite commonly where there is a drop from the balcony edge stalactites can form as seen in the picture below.
Is It a Defect That the Contractor is Responsible For?
Yes and no. Minimal efflorescence is not a contractor’s responsibility to fix outside of the 6 month minor maintenance period and should be looked after by the homeowner. AS 3958.1-2007 Ceramic Tiles Part 1: Guide to the Installation of Ceramic Tiles includes efflorescence in the cleaning and maintenance appendix and indicates that mild efflorescence can be removed with a cleaning solution containing phosphoric acid.
Where there is extensive efflorescence or leaching has occurred it most likely means that there is a bigger problem than just white residue appearing on the tiled surface. In most cases it means that the waterproofing and drainage system of the tiled bed has failed and is allowing water to leach through the cement bed and not drain away sufficiently. The formation of calcium carbonate is normally the first sign there is a problem. While this is an aesthetic issue it should be used as a signal that water is not being sufficiently drained away from the balcony. If nothing is done further down the track more serious damage can occur such as drummy tiles and complete failure of the waterproofing system.
In buildings where the balcony is over a habitable room failure of the waterproofing system can be quite detrimental. In these instances the contractor will be held liable for rectification within the structural warranty period, because waterproofing the structure is a principle Performance Provision of the BCA
Can Efflorescence Be Avoided?
Most tiling and waterproofing experts will say no, efflorescence cannot be avoided completely, however it can be minimised and serious damage prevented. The priority is to limit the entry of water into the cement component of the tiling system and then control the exit of any water that does get in.
Chemical fixes such as sealers can assist but they are not as effective as physical measures. For rectification work, a chemical fix will most likely be the preferred option to save time and money.
Physical measures and good design are the most effective means of avoiding efflorescence and leaching. To reduce the entry of water a positive fall on the balcony away from the building to stop ponding of water is the most obvious measure however this is sometimes not enough.
Systems such as a double waterproof membrane or applying a sealer to the tiles and grout will assist. To control the exit of water an adequate drainage system is essential. For example, draining the water to a floor waste will help, though this is not always the most desired installation aesthetically. Another option is to install drainage outlets at the edge of a balcony, such as a spitter (overflow pipe), that will direct the exit of water and allow it to run through the cement bed rather than dam up and leach through grout lines or cracks.
Probably the other most important factor when trying to avoid efflorescence or leaching is simply ensuring a quality of workmanship is met. Making sure that the coverage of adhesive to the tile is at least 90%, use the right sized trowel for the job and ensuring that the adhesive is compatible to the surface which it is being affixed (your supplier will be able to advise you about this). These processes will increase the adhesion of the whole system which will result in less movement and less water penetrating and potentially building up underneath the tiles.
Bryan Vadas, TimeMasters
Andrew Golle’, Armont Rectification Builders & Consulting
Presentation by Colin Cass on Efflorescence at the Full Frontal Tile & Stone Expo