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Cleaning Colorsteel Colorbond and Colorcote Roofs

Roof Wash - How To Clean Colorbond and Colorcoat Roofs with Bio-Shield®

Including cleaning of:

Roof Wash of all Color coated steel roofs.

Should I water blast clean or use Bio-Shield to clean a color coated roof?
Water blasting colour coated roofs to remove fungal, moss and lichen growths 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 layer on older roofs will be uneven and can leave a striped effect on the roof after cleaning.
The best method for wash and clean these roofs is to use a mild exterior solution like Bio-Shield®.

A simple application 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 roof kept clean with Bio-Shield® will also prevent the build up of dead fungal and lichen growths and sludge in the spouting, reducing rusting and blockages that cause spouting to overflow in heavy rain.

Why choose Bio-Shield® for your D.I.Y Colorbond and Colorcote roof cleaning?

Bio-Shield® has been developed through 30 years of use in a demanding commercial environment so it works extremely well.
Bio-Shield® is a high quality product, and contains no bleach, acids or phosphates,
The high concentration of active ingredients in Bio-Shield® when compared to other outdoor cleaners means it will cost less per diluted litre and cover more area at a lower cost.

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How to clean a Colorbond Roof - Bio-Shield® Application Instructions

Most falls from roofs are by homeowners working on their own roofs on the weekend.
If you have any doubts about your ability to to carry out this work safely then do not attempt it.

Walking on 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 of the tile due to the design and it is supported by both the tile and tile batten underneath.
Avoid the ridge of the tile, this is the weakest part and will bend and buckle easily resulting in a fatigue crack forming at the apex of the dent. This will leak.

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

Place your ladder on firm ground at the point 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 spouting.
The first trip up the ladder should be made to tie it to the spouting, ideally with a bungee cord or luggage tie to prevent the ladder from slipping.  Colorbond or painted spoutings should have some protection placed between the spouting and ladder to stop  scratching of the coating.

Remove loose debris, tree leaves, dirt etc, from the roof surface. Cutting back overhanging trees will help the roof to clean up and help keep it clean.
The roof surface can be either dry or damp.

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 of water. Do not reconnect the tank until the water is free of frothing or odour.

Check the weather forecast, or rain radar - brief showers after application on a porous surface will assist the action of Bio-Shield®
Air temperature above 10 degrees C° will help to accelerate biocidal action.
Premix the Bio-Shield® 1 part to 20 parts water in the sprayer or a larger bucket.
The average roof on a 3 bedroom house will take 60 to 80 litres of Bio-Shield® applied with a garden pressure sprayer.

Bio-Shield Mixing Ratios
Clean Water Bio-Shield Concentrate Diluted Bio-Shield
1 Litre 50 ml 1.05 Litres
 10 Litres 500 ml 10.5 Litres
15 Litres 750 ml 15.75 Litres
20 Litres 1 Litre 21 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 vapour 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.

Fill your sprayer with the premixed Bio-Shield® solution and pump it up to pressure.
Dividing the area to be treated into sections makes application easier. 
Use the rows of tiles to help guide you say a spray path of 2 to 3 rows of tiles.
Starting at the highest point the ridge tiles, begin application to the surface in slow, even strokes. Allow the following stroke to overlap the previous stroke by 50% to ensure even and complete coverage. Once the row of 3 tiles is complete move down the roof and spray the next 3 rows.
Ensure the lichen growths are saturated through to the tile to ensure penetration of the solution to the roots and achieve a good kill.
Always treat the entire roof, darker colored roofs will hide the widespread black fungal growths. As the roof cleans up the treated areas will be lighter in color than the untreated areas giving a patchy appearance.

To ensure the treated surface stays wet for 10 to 15 minutes apply a second consecutive lighter coat of Bio-Shield to re-wet the black fungal growths.
This is best applied as soon as the first coat has dried enough to allow safe walking on the roof.

Chimneys, vent pipes and skylights can all be treated with Bio-Shield® while you are on the roof.
If you have achieved correct coverage the runoff should have an orange-brown color - this is a good sign and indicates that the Bio-Shield® has penetrated the cell walls of the fungal growths and that their death is unavoidable.


Any leftover Bio-Shield® solution will keep indefinitely and can be kept aside to use as a spot spray to touch up any areas that need it.
Over the next few days the orange-brown color will fade and the moss growths will begin to turn brown as they die off.
2 to 3 weeks after application the moss growths should be entirely brown and any lichen present will have undergone a slight color change. The black fungal growths will not change color, but will simply fade away.
If there are any green patches in the moss growths, the Bio-Shield® was applied too lightly to saturate the growth to the roots.  Spot spray these areas with the leftover Bio-Shield®.

The treated surface may clean up over the next few months providing it is exposed to rainfall; however it would not be unusual for a  dirty roof to take up to 12 months to fully clean up.
The more rain the surface receives, the faster it will clean up.
It is best to reapply Bio-Shield® at the first signs of re-growth. Typically this will be every 2 to 3 years.
Best practice would be to have the roof re-treated just as the growths become visible again.
Application will be easier, faster and use less diluted solution; any new growths will die off and the roof will clean up quickly.

Once the surface is clean Bio-Shield® will give optimal results with regular maintenance treatments.  This will protect the factory color-coating from damage and premature erosion caused by a build up of moss, fungal and lichen growths.
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Bio-Shield has been developed and used commercially for over 38 years to successfully remove moss, algae and lichen from just about every exterior surface on domestic, commercial and industrial properties. 
The same high quality product is now available for DIY and commercial use on homes and businesses throughout Australia
We are committed to supplying our customers the best outdoor cleaning product at the best price, complimented with the best technical advice and support in Australia.

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