How to clean exterior walls

It’s often gradual enough to be unnoticeable, but over time your outside walls can become soiled. Things like pollution, dirt, dust, leaves, pollen, mildew, mould, cobwebs and bird or bat poo can all accumulate and make your walls look old and dirty. Cleaning your exterior walls may sound like a massive task, but they should ideally be taken care of at least once or twice a year.

Regular cleaning makes the job easier, keeps your house looking great, and gives you the opportunity to check on whether there are any repairs or maintenance issues that might need attending to. The following information can be used to clean brick, masonry, stone, weatherboard and vinyl clad houses.


How to clean exterior walls
Regularly cleaning exterior walls will help keep them in good shape.

Pre-cleaning checks

Before you begin washing your walls you should:

  • Check windows, roof, and exterior moulding and note any repairs necessary.
  • If your walls are made from bricks, rock or masonry, check your mortar before you start. Make repairs and allow to dry for one week before washing.
  • Clear gutters.
  • Trim back any overhanging branches or shrubs that lean against the walls.


High pressure water cleaners

One of the best tools for cleaning exterior walls is a high pressure water cleaner. Not only will using this equipment save you a lot of effort by blasting off accumulated grime, you will also save water and cut down on the dangerous chemicals you might otherwise use. If you don't have a high pressure cleaner, you could even consider renting one.

Before you start cleaning, check your local council water restrictions before you start cleaning your walls. Even if your local area allows unrestricted access to water for cleaning, always try and be mindful of the amount of water that you use. Likewise, you should read the instructions and do a spot test on an inconspicuous part of your wall first, as pressure cleaners have the potential to damage paint, timber and brick finishes.


To help prevent damage, do not stand any closer than a metre to the wall and keep the hose moving back and forth rather than spraying directly on one spot. If you have weatherboard or vinyl cladding on your walls, be careful not to direct the water in between the cladding where it can get trapped. If you need to climb a ladder to clean higher floors or tall walls take extra care, as the pressure can easily push you backwards off the ladder.

If you choose to use a detergent with a high pressure cleaner, make sure it's safe to use in the cleaner. Try and use a mild, environmentally friendly detergent if possible.


Garden hoses and brooms

If you’re not using a pressure cleaner you will either need an attachment for your garden hose, or a long handled broom and ladder. Wash the walls from the top down, so that you're not letting dirt run down over bits you've already cleaned. If you're using detergent, you should wash the walls a second time with plain water to rinse off any residual soap.


Mould and mildew

If your walls need mould or mildew removed, try scrubbing the affected areas with borax and water. Bleach will also kill mould but can be harsh on you and the environment. If you choose to use bleach, wear old clothes and protective goggles and breathing gear. Water any plants near your walls first - this will stop them absorbing too much bleach. If your plants are especially sensitive, consider adding a small amount of limestone to your garden to neutralise the acidity of the bleach.