Regular roof maintenance and repair is an important part of home maintenance, but is often overlooked until major problems developed. Periodically, it is a good idea to have a roof repair and general maintenance specialist come to your home and give your roof a thorough inspection and cleaning, but just as regular tooth brushing helps prevent major problems occurring between visits to the dentist, if you regularly clean your roof yourself, you can keep it looking like new and avoid major expenses over time. This guide to cleaning the roof will help you decide if it's a job you can do yourself or one you should leave to the experts.

Two Ways to Clean the Roof

The type of roof you have is going to determine how to most effectively clean your roof. That black patches you see on so many old, poorly maintained roofs is caused by algae. Whatever cleaning method or solution you use is primarily going to be for removal of this algae. There are two basic ways to remove algae from your roof:

1. Pressure washing: If you have a metal or tiled roof, pressure washing is an effective way to remove algae.
   
   
2. Chemical washing: Any type of roofing material can be cleaned with chemicals. The most commonly used chemicals for cleaning the roof are sodium hydroxide or chlorine solutions.

How to Pressure Wash Your Roof

The first thing you'll need to do is go to your local equipment hire shop and rent a pressure washer or, if you have other uses for one around the house, there are many inexpensive models designed for home use available at hardware stores throughout Australia. Pressure washing is a safe and easy way to remove algae, but it is not foolproof. This is what you need to do to pressure wash your roof the right way:

• Start at the peak of the roof and work your way down, to avoid blasting water up between overlapping tiles or sheets of roofing materials.
  
  
• Start with a small area first, keeping the head of the wand about 30cm away from the roof and using medium pressure. Gradually lower the wand until you can see that it is removing the mould. If the pressure is too heavy, you could damage some types of roofing materials, so take it slowly and regularly inspect the roof as you go.
  
  
• Stand on a dry area to begin with. As you progress, stand on areas that you have already cleaned. Algae becomes very slippery when wet, so be very careful not to stand on wet, unclean roof areas.

Cleaning with Chemicals

Chlorine is usually a better choice for do-it-yourself roof cleaners than sodium hydroxide because it is safer and more forgiving, but you can use a weak sodium hydroxide solution if you are careful and thoroughly rinse the roof before the solution has a chance to dry. Whichever chemical you choose, be sure to wear protective gloves and eye glasses, since even a weak solution can cause skin and eye irritation. The trick to using chemicals is to let them do the job for you as much as possible. They will quickly kill algae and moss, which you can then simply rinse off the roof using a garden hose. You can help speed up the process by applying the solution with a soft bristled brush and then brushing as you rinse, but hard scrubbing can do more damage than good.

Safety Tips

• Do not attempt to clean a steeply pitched roof yourself. When the roof is dry and clean, you may be able to safely walk on the roof, but when you are cleaning a wet roof, it becomes slippery and if it is algae-affected, it becomes extremely slippery.
  
  
• Avoid strong chemical solutions and avoid rinsing them onto the lawn or plants below. The same chemicals that kill the algae on your roof can kill the plant life you want to thrive in your garden.
  
  
• When pressure washing, use the minimum pressure needed to remove algae. While you can quickly remove algae under high pressure, you can also easily damage your roof.

Finally, don't hesitate to call a roofing professional if you are in doubt about your abilities. They have the equipment and expertise to do the job well and do it safely.