Roof Maintenance Cleaning

Roof cleaning is important maintenance and shouldn't be overlooked.

We’re not here to tell you that roofs are an important fixture on your building. From providing insulation to keeping you and your dry, you know that already. What you might not know, however, is that your roof should be maintained regularly to preserve its integrity. Roofs tend to be out of sight & out of mind and they can become the most neglected area of a building but a low-pressure chemical or chemical-free hot wash every 12 – 24 months is an investment.

In proportion to the rest of your property, they are a significant surface area and they are a big landing pad for airborne dirt, salts as well as bird droppings and leaves. Most modern roof surfaces are painted or powder-coated – if dirt and corrosive elements are left indefinitely they will soon eat through these thin-film coatings and corrosion will start. This means premature re-painting or at worst, replacement of damaged sheets or flashings.

Most manufacturers recommend maintenance cleaning to maintain their warranty, one NZ supplier recommends the following;  ‘Regular washing may be anything from 3 monthly to 12 monthly periods. Washing should either be with a stiff soft bristled brush or water blasting at a pressure of 1500-2000 psi.’

A roof replacement is not cheap and apart from regular washing – there are other ways you can extend the life of your roof. Here are a few;

  • Minimise the number of penetrations and fixtures mounted on the roof. The fewer service people that have to walk on your roof the longer it will last. Spans between purlins are wider than they used to and the wrong weight in the wrong place will dent and warp the roofing iron, potentially causing leaks.
  • If you have HVAC and other plant on the roof which needs servicing – install an approved access and walkway system for safer access. It also mitigates the above issue.
  • Have a ‘no screw left behind policy’ In our travels, we’ve noticed one of the biggest causes of spot corrosion on a roof is from nails and roof screws left lying about by installers or service people. They will cause rust spots in no time at all. Make sure your service people are aware of this

What is the best method of cleaning?

A Low-pressure chemical wash works well, a detergent loosens up the dirt for easier cleaning and longer-lasting results. Whilst our chemicals are highly diluted and biodegradable, care is needed for containment of run off into the waterways and sometimes we can not offer this option.

Chemical-free cleaning is also effective using Hot water – hot water cleans 80% better than cold and the heat can kill off moss spores as well. This is a great option as it generally uses less water and as the name suggests – no chemicals!

Soft washing is another popular option, that’s our term for spray-on Moss and Lichen treatments. A Broad-spectrum specialist biocide solution is sprayed on your roof surface and left to weather wash clean over time. A slow but long-lasting clean especially good for coated metal and masonry tile roofs – but equally effective on iron as well.

See our Moss Spray Treatment page and our FAQ and Knowledge base pages for more information on roof care.

Don’t forget the Gutters

Remember, most of the dust that lands on your roof runs off into the gutters and builds up a mud layer, it also forms a base for moss and lichen to grow through moisture retention. Gutter cleaning is included in our roof washing as it is equally if not more important. See our Gutter Cleaning page for more details

Large Coolstore roof - mid clean
Large birds can wreak havoc on roofs - this is a Seagull nest.
This image shows the difference between dirty and clean sections of a roof wash while in progress
This shows why a 'no screw left behind' policy is a good idea..
Working from an EWP is a safe way to clean a roof when possible.

Annual cleaning of roof surfaces is recommended as a minimum in most parts of NZ, remember that airborne salt and dirt build up on the surface should be removed through washing to prevent premature corrosion and rusting (note – rainfall may remove some salt but it generally not strong enough to remove dirt and other contaminants).

If your building is in a coastal or direct sea spray zone such as many parts of Auckland & Wellington, you should consider 6 monthly cleaning as the rate of corrosion will be much higher. Our teams can recommend a cleaning programme that will maintain your roof – and one that will suit your OPEX budget.

It’s a good idea to check your roof warranty to see the manufacturers cleaning requirements.