The lime water in this image shows the path of water penetrating the tiled surface, starting as rainwater and leaving as lime water, which hardens as ugly-looking calcium deposits.
The more water can penetrate the surface, the more lime water is created and the worse it looks. In this example water is leaching through the screed bed at the top level and exiting at lower openings wherever holes allow it to leave.
What is efflorescence?
The technical definition: Efflorescence is defined as the process of losing water or hydration from a hydrate. (Crystalline deposits on the surface of masonry.)
How is efflorescence formed?
The construction sector: it is described as an accumulation of calcium crystals and or salts that disfigures the top, edges or underside of masonry structures and is caused by water entering and exiting porous building materials such as concrete, bricks, tiles, sand cement etc. drying to leave a salt residue.
Leaching calcium is a root cause of a problem with materials that do not allow for building movement as well as the use of possibly inferior liquid applied membranes.
Secondary efflorescence, also known as leaching, occurs only when continuous or cyclical saturation of a cement based material allows free lime or other salts within the masonry to be dissolved and to migrate to the surface.
Secondary efflorescence can be very difficult to stop, and may continue to leach out of the masonry for many years.
The screed below the tiles is penetrated by water, a problem that begins at the vertical and horizontal junctions.
Water beneath the tiles mixes with calcium oxide, (an ingredient found in cement) and transforms through a chemical reaction into a calcium hydroxide solution, commonly known as limewater.
The limewater rises through a capillary action to excrete at the top of the tiles or with controlled falls off the edges, the carbon dioxide in the air harden as calcium carbonate.
A chain reaction occurs as air and water enter then exit through the tiles and increase the amount of visible leaching as found on the facade of the house.
Failing waterproof systems
Extensive efflorescence or leaching that has occurred to the extend found on the residence means that there is a bigger problem on the drainage system of the tiled bed and is allowing water to leach through to the cement bed and not drain away sufficiently.
Calcium carbonate formation is often the first sign …
While this is an aesthetic issue it should be used as a signal that water is not being sufficiently drained away from the tiled area. If action is not taken as soon as possible a more serious damage can occur such as drummy tiles and complete failure of the waterproofing system.
How to minimise efflorescence
If you can control the movement of water through the cement materials that make up your wet area tiling system, then you can control efflorescence. If efflorescence is to be controlled, it is necessary to have a positive fall in the substrate and finished surface.
The two general principles for minimising efflorescence are:
- Minimize the entry of water into the tile screed.
* Treat the cured tile screed with a penetrant or additive that is compatible with the membrane and the tile adhesive.
* Apply a secondary membrane over the cured screed and, seal the surface of the tiles and grout joints with a sealer.
- Allow water that penetrates the screed to drain away. Positive Falls.
* Create positive falls. This system relies on draining any water that penetrates the tile screed to a designated outlet. It is a primary requirement of this method of controlling efflorescence to have positive fall to drainage. This system should not drain to a free edge unless the salt laden water is collected by a gutter.
* Install water stop angles at free edges and there must be positive fall in the substrate from the water stop to the drainage outlet. The drainage outlet must be designed to allow soluble salts to enter the drainage system at the neck of the grate.
Because efflorescence is such a large problem, good practice combines the precautions of principles 1 and 2 above.
Quality workmanship will help you avoid efflorescence
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 .
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.
Minimal efflorescence is not a contractor’s responsibility to fix outside of the defects liability period and should be looked after by the homeowner. You can remove it with a cleaning solution containing phosphoric acid available at local hardware stores.
In most cases it is advanced secondary efflorescence known as calcium leaching, a visible defect and a failure of waterproofing and tiling techniques that if not addressed will worsen and is likely to eventually fail.