Pressure Washing Sandstone Buildings - Care is Needed
Sandstone, that foundational Australian building block, is beautiful and durable. If it is treated with care it will maintain its beauty and strength for a very long time.
However if it has not been sealed or if it is inadequately sealed, its surface can become soft and crumbly with pieces breaking off and weathering away. Sandstone that is not adequately sealed can easily be damaged by a high pressure sprayer. The water may be cold, warm or hot without being harmful, it is the force of the water as it hits the surface of the stone that can cause damage. When carried out correctly, however, sprayer washing is one of the safest and gentlest ways to clean sandstone.
Care also needs to be taken to ensure that water does not penetrate through to the interior of a sandstone building. Too high a pressure, too great a volume of water, insufficient sealing of the sandstone, and inadequate drainage of the runoff water are all things to watch out for. Anyone planning a full wash of a sandstone house needs to consider these in advance. Heritage building recommendations are that the water pressure is set to a maximum of 200 psi.
Using the correct detergent is also essential. Certain chemicals erode the sandstone while others may be inadequate for removing the dirt, mould or stains. It is important to get professional advice on the best detergent to use on your particular sandstone building. You also need to have a clear understanding of the condition of the sealant, and of any grouting or adhesives, before beginning a pressure wash.
Note: If your sandstone building is heritage listed then certain regulations apply. You will need to contact a professional who has the training or certification for cleaning and treating such buildings.