Pressure Washing Your Roof - DIY or Professionals?

24-Nov-2018 By BWS

Pressure Washing Your Roof - DIY or Professionals?

You have pressure washed areas around your house and now you're looking at your roof.  It appears to have a thick film of dark gunk on it, some unidentified mixture of mould, gritty dust, bird droppings, smog, lichens and decaying foliage. Leaves, twigs and the odd small branch are also visible. No question, the roof needs cleaning. Does this necessarily mean heading up there yourself with a high pressured power washer? 

What are the risks, whether to the roof itself or to the person working on it?  It might be worth taking a bit of time and thinking about the project before getting underway.  

A few questions worth considering:

1.  What are the surface materials on the roof?  Is it a colorbond or metal roof?  Are there concrete or terracotta tiles?  Is the roof of shingles or slate?  Are there solar tiles on the roof and is glass a component?   For most of these materials to be cleaned safely with minimum risk of damage, a low pressure soft wash is recommended.  This means keeping your standard pressure washer on a low psi throughout, eg 500 - 1,000 psi, and using the best detergent or other ingredient to remove the gunk. Stay on the low pressure while rinsing as well as washing. 

2.  How high is the roof, and is it steep or curved?

3.  Is the house single storey, double or higher? Is it gabled?

4.  How old is the roof, and when was the last time someone was working on it?  Is it stable or brittle?

5.  Are there any weak spots on the roof, either where tiles have shifted or cracked, metal has rattled or a leak has appeared?

If any of the questions listed above raise further queries or leave reasons for concern about the situation, it's advisable to call a professional roof cleaner and at least get their advice on what is needed.  Next, if you still intend to go ahead with it yourself, some relevant safety precautions are listed below.

Safety on the Roof 

1.  The general safety precautions for using a pressure washer apply, of course.  These include wearing strong rubber soled footwear for gripping as well as work gloves, eye protection and clothing that protects your arms and legs.

2.  A strong, sturdy, secured extension ladder will be needed. 

3.  Have at least one other person nearby while you're on the roof. 

4.  Disconnect your rainwater tank before you begin cleaning the roof.

5.  Safe Work Australia recommends the use a safety harness if any of the following conditions apply:  If the house is higher than single storey, if the roof has a sharp raised angle or steep curve, if the roof is slippery, if the roof is damaged or fragile, or if weather could disrupt the work either by wind or rain.  BHG outlines use of a safety harness here.

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