Cleaning Colorsteel, Colorbond and Colorcote Roofs 

How To Clean Colorsteel, Colorbond and Colorcote Roofs with Bio-Shield®

Including cleaning of:

  • Colorsteel, Colorbond and Colorcoat  Longrun and Colortile Roofs
  • Colorsteel, Colorbond and Colorcoat Claddings
  • Colorsteel, Colorbond and Colorcoat Spoutings
  • Painted and Recoated Roofs
  • Skylights - Glass, Polycarbonate and Fibreglass
  • Polythene Herd Homes and Grow Houses

Should I water blast clean or use Bio-Shield® to clean a color coated roof?

Water blasting color coated roofs to remove, moss, algae and lichen may damage the surface.
The pressure required to fully remove lichen will remove the protection provided by the oxidised surface layer, reducing the thickness of the coating and exposing the un-oxidised paint film to sunlight and weathering. The removal of this oxidised layer on older roofs will be uneven and can leave a striped effect on the roof after cleaning.

Water blast cleaning is a time consuming, expensive, and ultimately futile way to clean these surfaces: if they are not sterilised in conjunction with water blasting, the lichen residue and spores on the surface will quickly regrow and discolor the roof again. 
Most roofs will leak with high pressure water jetting especially tile roofs.

The best method for cleaning and maintaining color coated roofs are exterior cleaning solutions like Bio-Shield®.

A simple application of Bio-Shield will kill and remove the growths and keep the surface clean for extended periods. 
Regular lighter applications of Bio-Shield at the first sign of re-growths will effect a rapid clean up and keep the surface clean again for an extended period.
A color coated roof maintained in a clean condition with Bio-Shield will also prevent the build up of dead moss and lichen growths and sludge in the spoutings, reducing rusting and blockages that can cause spoutings to overflow in heavy rain.

Why choose Bio-Shield® for your D.I.Y Colorsteel roof cleaning?

Bio-Shield® has been developed through 39 years of use in a demanding commercial environment so it works extremely well.

Bio-Shield® is a high quality product, and contains no bleach, salts, acids or phosphates.

The high concentration of active ingredients in Bio-Shield® when compared to other outdoor cleaners such as Wet and Forget and 30 Seconds means it will cost less per diluted litre to cover more area at  lower cost.

Bio-Shield - Lichen, Moss and Algae on Asphalt Shingle
Colorsteel Tile Roof Cleaned with Lichen
Colorsteel Tile Roof Cleaned with Bio-Shield

Bio-Shield® Application Instructions

CAUTION - Bio-Shield is OK to use on house walls with Colorsteel Cladding and on windows. If the surface is not exposed to rain e.g. under the eaves or high on the wall, it will need to be washed down to assist removal of the Bio-Shield and dead growths.
Care should be taken when using Bio-Shield around old powder coated aluminum window frames, where the powder coating is oxidised. Most types of outdoor cleaners will leave marks on the darker colours that have oxidised (aged). 


Most falls from roofs are by homeowners working on their own roofs on the weekend. Dirty color coated roofs are slippery when wet so extreme care needs to be taken to prevent a fall.

Check out the Jet-Stream Applicator - you can to spray an average sized roof from a ladder. If you have any doubts about your ability to to carry out this work safely then do not attempt it.

We have an application service here at that will quote on treating your roof. From around $290 the work can be done with no risk to yourself.

Walking on Pressed Metal Tile Roofs

To prevent damage to pressed metal tiles the best place to walk is in the centre of the tile at the bottom edge, in the 'pan' of the tile 
This is the strongest part due to the design and is supported by both the tile and tile batten underneath.

Walking on Longrun Roofs

To prevent damage to longrun sheets avoid walking on the rib unless your foot is placed directly on the screw head.  Walk in the pan of the sheet where its supported by the timer batten underneath.    


For a successful DIY job, preparation is the key. Following these simple steps will ensure a professional looking finish and long lasting protection against regrowth damaging your roof.

Place your ladder on firm ground at the point preferably where the distance between roof and ground is smallest. For every four metres in height the ladder base should be placed 1 metre out from the spouting. The top of the ladder should extend at least 1 metre above the edge of the roof to make entering and exiting the roof as safe as possible.
Placing the ladder against the spouting brackets will reduce the possibility of breaking PVC spouting or deforming metal spoutings.
The first trip up the ladder should be to tie it to the spouting, ideally with a bungee cord or luggage tie to prevent the ladder from slipping. Coloursteel or painted spoutings should have some protection placed between the spouting and ladder to stop scratching of the coating.

Remove any loose debris, tree leaves etc, from the roof surface. Cutting back overhanging trees will help the roof to clean up and help keep it clean.

Check local governing body regulations for discharge of wash water into the storm water system.
If you are on tank water disconnect the tank from the roof. It will need to stay disconnected for 2 to 4 weeks, and until the roof is flushed by enough rain to remove all traces of the Bio-Shield from the run off water. Do not reconnect the tank until the water is free of frothing or odour.

Check the weather forecast, or rain radar - no rain for 3 to 4 hours
Air temperature above 10 degrees C° will help to accelerate biocidal action.
Premix the Bio-Shield® 1 part to 20 parts water in a pressure sprayer.
If using the Jet-Stream Applicator, follow the instruction on the back label.

Bio-Shield® Mixing Ratios - for Pressure Sprayers

Clean WaterBio-Shield ConcentrateDiluted Bio-Shield
1 Litre50 ml1.05 Litres
10 Litres500 ml10.5 Litres
15 Litres750 ml15.75 Litres
20 Litres1 Litre21 Litres


If you have a respirator, now is the time to put it on, along with a pair of gloves and soft soled shoes and/or a pair of long pants. If you don't have a respirator, try to stay upwind during application. Evaporation of the solution on a warmer day will generate vapor that should be avoided where possible.

Application is best done on an overcast day at any time of the year, or early morning and late afternoon in summer if a warm sunny day is forecast. This slows evaporation and speeds the treatment process.

Saturation, then keeping the surface wet for 10 to 15 minutes is the Key to Success

Fill your sprayer with the premixed Bio-Shield® solution and pump it up to pressure.

Always treat the entire roof, darker colored roofs will hide the widespread black algae growths.

Dividing the area to be treated into sections makes application easier - using the lines of the sheets or rows of tiles to help guide along the spray path.

Ensure the lichen growths are saturated, with penetration of the solution to the roots.

Starting at the ridge, begin application to the surface in slow, even strokes. Allow the following stroke to slightly overlap to ensure even and complete coverage. Once the section is complete move down the roof and spray the next 3 rows.

Apply a second lighter coat after 10 to 15 minutes to any areas with black algae. 

This second coat is essential to ensure a good kill of these algae.

Chimneys, solar panels, vent pipes spoutings and skylights can be safely treated with Bio-Shield® 

Clean Up

Over the next few days the lichens will begin to change color as they  die off.

For the initial clean up, it may take 3 to 12 months for the roof to fully clean up as rain progressively washes the dead growths away.

Cleanup times are dependent on how much growth is on the surface, the condition of the surface and the amount of rain that falls.

The cleanup process can accelerate in the 9 to 12 month period as the dead growths are softer and more easily washed away.


Once your roof is clean, Bio-Shield will give optimal protection with regular treatments.

Best practice is to reapply Bio-Shield at the first signs of re-growth. Typically this will be every 2 to 3 years. On lighter colored roofs, light regrowth's are more noticeable. especially on the South sides.

The two or three yearly applications will be easier, faster and with a spread rate up to 8m2 per diluted litre, will use less solution. Any light new growths will die off and the roof will clean up quickly.

Any areas of the roof where birds habitually sit and areas under trees, TV aerials or pipes that discharge water onto the roof, will show re-growth's first and can be spot treated as required.