Well the technical name is Efflorecence
It can also appear on concrete!
What Is Efflorescence, & How Is It Caused?
Basically it is caused by water soluble salts contained in either the mortar, or the bricks.
When any water in the wall (that has dissolved the salts) comes to the surface of these building materials the water evaporates, leaving the salts on the surface.
Although the salts sometimes come from the bricks, more commonly they originate from the mortar.
Although some efflorescence may be as a result of the initial construction water; walls that are regularly wetted can have more persistent issues, for instance:
- Uncapped garden walls.
- Retaining walls.
- Walls exposed to driving rain.
Efflorescence is more prevalent on South and East facing walls as these are colder so the moisture gets to the face of the wall. North and West facing walls are generally warmer so the water evaporates before it reaches the surface leaving the salts inside the walls.
What Can Be Done To Prevent Efflorescence?
There are several things that can be done to minimise efflorescence including:
- Overall design to keep water out of the wall structure.
- Specifying Mortar Joints to keep water off the wall.
- Protecting bricks from weather before they are laid
- Specifying low alkali cement.
- Specifying Washed Sand
- Using a mortar admixture to minimise the water cement ratio.
Dealing With An Existing Problem
Probably the first step when dealing with an existing problem is ensuring the wall can be kept dry.
As long as there is a path for water to get to the surface it will be very hard to deal to achieve a permanent solution as water will continue to evaporate on the surface bring out fresh salts.
When removing the actual efflorescence its best to try a stiff brush first.
If this doesn’t work you can try hand washing again using a stiff brush. (Although it is tempting to wash the soluble salts off with a pressure washer the water can penetrate into the wall and then as the brickwork dries bring further salts to the service)
The final suggestion is to use a special chemical efflorescence removal chemical. (These tend to be acid based and need to be used exactly as the manufacturers recommend)
See Bricks for more posts