Brick Cleaning - treating mortar stains
by Megan Macpherson
Are your house bricks looking worse for wear? Have they been covered in mortar droppings by a careless brick layer? Cleaning brickwork will enable you to maintain the exterior of your home, for a fairly low cost. The Clay Brick Association of NSW offers some technical advice about removing stains, while ensuring the integrity of your brickwork is upheld. This information pertains to mortar droppings.
If you have mortar stains or droppings on your clay brickwork, there is a way of removing them. However, the easiest way to avoid this is to ensure that the bricklayer takes care to remove the mortar droppings as they go, before the mortar becomes hard. It is important to remove mortar droppings correctly, otherwise mortar joints and brickwork may be at risk of damage from high pressure hosing. Hydrochloric acid will remove the mortar by dissolving the cement element, and can be used for this type of stain only. The amount of acid needed varies, for light clay bricks use one part acid to 20 parts water, and for darker clay bricks use one part acid for 10 parts water. Acid is harmful to skin, so ensure that you take adequate safety precautions such as gloves and safety equipment such as goggles. If acid comes in contact with skin then flush with water.
Remove any large mortar droppings from the wall manually before you begin. Only remove mortar if it is three days old at least. However, after two weeks it will be much harder, as it has cured, so the optimum time for mortar removal is between these times. If there is any white residue on the wall, this is a salt, and can be brushed off with a hard brush, not washed with water. After this is removed, then thoroughly soak the wall with water, and ensure that it is wet once you start cleaning.
Work with an area of 2-6 metres square at a time. Brush the acid solution onto the wall with a brush, broom or low pressure hose, starting from the top of the wall. Wash off with a high pressure hose from top to bottom after leaving the solution on the bricks for three to six minutes.
Care must be taken when using a high pressure hose on brickwork, as it can undermine mortar joints, as well as drive chemicals into the bricks and ultimately affect the stability of the wall. Therefore the hose must be used at a pressure of no more than 1200 psi, and held at an angle of no less than 15 degrees. Remain about 50 cm from the wall, and no less than 30 cm. If necessary, repeat the washing and rinsing process, as opposed to hitting the wall hard in one go. If you don’t have a high pressure hose, then simply wash the wall by hand. This method is more appropriate for smaller jobs.