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Cleaning Timber Decks

How To Clean Timber Decks with Bio-Shield®

Including cleaning of:

Hardwood, Softwood and Composite Decks.

Should I water blast clean or use Bio-Shield to clean a timber deck?
Water blasting a timber deck to remove fungal, moss and lichen growths will severely damage the surface.  The pressure required to remove moss, mould and lichen will damage the timber fibres leaving deep gouges and a furry striped finish. Not a good result.
The best method for cleaning timber is to use a mild exterior cleaner like Bio-Shield®.

Treating a  deck with Bio-Shield will kill and gently remove the growths then 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 deck that is kept clean with Bio-Shield® will also prevent the build up of black fungal and lichen growths that make a deck slippery and dangerous to walk on when its wet.

Why choose Bio-Shield® for your D.I.Y Deck 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 Timber Deck - Bio-Shield® Application Instructions

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 timber deck.

Remove pets toys and feeding bowls from the area to be treated.
Keep children and pets off the treated surface until it dries.
Do not feed pets on the treated surface for 3 to 4 weeks.

Remove loose debris, tree leaves, dirt etc, from the roof surface.
Cutting back overhanging trees will help the deck to clean up and help keep it clean.
The timber surface should be dry to maximise absorption of the Bio-Shield solution.

Check the weather forecast, or rain radar - ideally no rain to 1 to 3 hours is the minimum requirement for treating timber.
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.
Coverage will vary from 3 to 6 m2  of diluted Bio-Shield, depending on the type of timber, how much growth is present and the weather conditions on the day.

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 gumboots 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 once the deck has dried or in 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.
Timber decks must be thoroughly saturated and this will take  2 to 3 consecutive coats to achieve and keep the timber wet for the 10 to 15 minutes required for the Bio-Shield to kill.
Apply is slow even strokes allowing the following stroke to overlap the previous stroke by 50% to ensure even and complete coverage. Ensure the gap in between boards is treated by angling the spray head into the gap.
Always treat the entire deck and apply  enough coats to ensure the deck stays wet for 10 to 15 minutes after the application be lighter in colour than the untreated areas giving a patchy appearance.

To ensure the treated surface stays wet for 10 to 15 minutes apply a second and third consecutive  coat of Bio-Shield to re-wet the timber.

Planters, steps railings, either glass or timer can also be safely treated with Bio-Shield.
The deck may change colour as the Bio-Shield takes effect with a change in to an orange-brown colour - 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.

On heavily infested timber the surface will need some extra work to assist with clean up.

After 3 to 4 weeks, hose and brush down the deck with a stiff yard broom to agitate and loosen the surface.
Flush the deck with clean water to remove the sludge.
This step is only required for the initial clean up.
Apply Bio-Shield at the first sign of re-growths to keep the deck clean and avoid this extra work. If treated regularly the deck will stay clean,


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 colour 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 will continue to clean up over the next 3 to 12months providing it is exposed to rainfall. 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 6 to 12 months2 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 deck will clean up quickly.

Once the surface is clean, Bio-Shield® will give optimal results with regular treatments. 
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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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