Firstly it must be understood that there is a big difference between efflorescence and laitance. Laitance is a sign of over-wet mixture or overworking or improper combination of mixture in building material whereas efflorescence, or rising damp, is a natural process of migration of water-soluble salt deposits to the surface of porous material. In other words, laitance (which comes in the form of a fine, pasty cement layer) is bad and efflorescence (which is a whitish, crystalline deposit on the surface of masonry, stucco or concrete) is normal.
Efflorescence is very difficult to avoid, though by using top quality building bricks and building sand, the visual effects of efflorescence can be avoided as much as possible. Here are a few things that you can remember when examining building materials and signs of efflorescence on brick/paving surfaces.
- The process of efflorescence depends on humidity; when humidity is higher, water evaporation is slower and vice versa. Fast water evaporation means that salt deposits may be left beneath the surface and less visible whereas slower evaporation will make ‘whiskers’ growth more visible to the surface. This means that the process of efflorescence depends on season, weather and other environmental elements.
Installing weep holes in the concrete base for better drainage will decrease the visibility of efflorescence, while sealer products can help to eliminate the appearance of efflorescence further.
- Protecting the masonry or cement surface from external water sources will minimise the effects of efflorescence, especially during the first few years of the new structure. Rain, sprinklers and cleaners that allows extra water to seep through brick voids will increase the signs of efflorescence on the surface, so ensure that the surface is protected from excessive and unnecessary contact with water.
- Efflorescence will turn into powder when rubbed between fingers and it will dissolve in water. If the deposit on the surface does not do this, the substance may actually be mould, in which case a professional inspector should be contacted.
- A mild acid solution such as white vinegar or baking soda can be used to clear signs of efflorescence. Always wet the surface with some water before applying an acid solution and ensure that the surface is dried again properly once the job is done.
- Even after cleaning powdery evidence, signs of efflorescence may appear until its natural chain is broken or completed. Since the process is affected by seasons, intensity of efflorescence may fluctuate; however after many months (even up to 3 years) the process should be finished and signs of efflorescence will deplete until completely vanished.
You may want to read more on drainage and erosion control to prevent the effects that water has on your landscape.