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Ask Andy®

Thanks Andy for the advice - nice to talk to someone who really knows their product.
Paul - Tauranga. November 2019


  Is Bio-Shield safe to use for Moss Removal or Lichen Removal?
     Yes, Bio-Shield has been used commercially and safely for over 35 years on just about every external building surface,   
     including roofs, walls, painted surfaces, concrete paths and drives, asphalt, and tennis courts.
     It contains no bleach (chlorine), phosphates, is non-acidic and fully bio-degradable once diluted.
     Follow the simple safety instructions on the bottle.

  What does cost per diluted litre mean?
    Cost per diluted litre is the true cost of any brand of exterior cleaner once it has been diluted to its recommended  
     For example;
     A 5 litre of Bio-Shield costs NZD$97 and makes 105 litres - $97 divided by 105 litres gives a cost of 92 cents per litre.
     A 5 Litre of Wet and Forget costs NZD$99 and makes 30 litres - $99 divided by 30 litres gives a cost of $3.30 per litre.

    Is Bio-Shield available to buy in a store near me?    
     No, Bio-Shield  is only available on-line or by phone order.  It can be picked up from Ellerslie, Auckland by arrangement -
     phone 0800 800 127 prior to collection.
     Courier delivery is usually on the next working day in Auckland and North Island and in 2 to 3 days in the South Island. 
     Rural delivery can add one day to delivery time.

   Do Outdoor Cleaners really reactivate with rain for up to 12 months?   

     Many products with the same active ingredient claim to remain on the treated surface and be reactivated
     by rain for up to 12 months.
The active ingredient in this class of outdoor cleaners is 100% water soluble, and that means several falls of rain will 
     wash it away, usually within 1 to 4 weeks,  even on a porous surface.
     Bio-Shield works to protects a surface from regrowth for up to 4 years by completely and easily killing 99% of all     
     growths and the
spores of these growths, before weather removes them from the surface.
     Regrowth will naturally occur over time as new spores are deposited on the surface and begin to regrow when
     conditions are suitable.

   I live in Australia, How can I get Bio-Shield?
     Bio-Shield can be shipped direct to you anywhere in Australia, most cases in 1 to 3 working days.
     Freight is an additional cost and starts from $9.95.
     Even with shipping added, Bio-Shield is still up to 70% cheaper per diluted litre than buying Wet and Forget in Australia
     Orders can be placed online here,, or by phoning 1800 236 810.

   Will Bio-Shield kill my plants?
     No, Bio-Shield will not kill plants if used carefully by avoiding direct spray onto foliage. In some cases it may cause minor
     spot damage to the leaves of delicate plants.   If in doubt, rinse the leaves off with water.

  What is the coverage rate of Bio-Shield?
     When used on concrete or similar porous surfaces, the coverage will vary from 3 to 6 m2  per litre.   
     A 5 L bottle of concentrate will cover 300 to 600 m2
    When used on Coloursteel or similar smooth, painted surfaces, the coverage will be 4 to 8 m2 per litre so a 5 L bottle of 
    concentrate will cover 400 to 800 m2

    If the moss or lichen growths are thick and heavy, the spread rate will be reduced.
    If application is carried out on a hot day, the spread rate will also be reduced due to rapid evaporation.

    The Jet-Stream Applicator will cover from 150m2 on concrete, up to 300m2 on Colorsteel with low to moderate growths

  What size bottle should I buy?   
    The 2.5L Jet-Stream Applicator is the ideal size for smaller concrete areas, such as townhouse courtyards, paths and
    driveways.  It will spray 100m2 of concrete in under 5 minutes.
    It is also suited for the treatment of small Coloursteel roofs on a 2 or 3 bedroom home without a garage under the main
    roof.   The Jet-Stream Applicator is reusable and refillable with Bio-Shield concentrate so you will continue to get the a

    The 5 litre bottle is best for medium to large concrete areas, concrete and stone chip coated roofs, and Coloursteel roofs
    on medium to large homes.  It will make up 105 L of Bio-Shield at a cost of $0.94c per diluted litre.

    If you intend to maintain any exterior surface with regular treatments of Bio-Shield, I would recommend the  2 x 5L
    or the 20L to get the best value for money.  Bio-Shield has an unlimited shelf life, either diluted or undiluted so can
    be stored indefinitely.

   Can Bio-Shield be used on house walls?
     Bio-Shield is OK to use on house walls and windows.  If the surface is not exposed to rain it will need to washed
     down to assist removal of the Bio-Shield and dead growths. Windows will need to be washed down soon after the  
     application to remove the Bio-Shield residue  Bio-Shield is ideal for pre-paint preparation of any surface, followed by
     wash down or water blast clean.  Care should be taken when using Bio-Shield around powder coated aluminium
     window frames, where the powder coating is oxidised.  Most types of outdoor cleaners will leave marks on the darker
     colours that have oxidised (aged).  These should be washed down immediately after the Bio-Shield application
   Can I add weed killer (glyphosate) to Bio-Shield when I spray my cobbles or brick pavers ?
     Yes; add the required amount to the sprayer when using Bio-Shield to treat paving with moss, grass, or weed growths
     in cracks or joins.  Ensure the treated surface stays dry for 3 to 4 hours to allow the weed killer time to work.

   Will Bio-Shield harm my pets if I clean my paths and deck?
     Bio-Shield is OK to use around pets providing some basic precautions are taken.  Remove feeding / water bowls,  
     bedding and toys from the area to be treated, and keep pets off the treated surface until it dries.  Do not feed pets on 
     the treated surface until it has been flushed by rain.

   How long is the shelf life?
     Unlimited when kept in a closed container - whether diluted or undiluted.

   How long will it take to clean up the surface I have treated?
     Concrete surfaces with light to moderate growth will take 2 to 4 months to clean up. Other surfaces will take from 3 to
     12 months to clean up. The amount of growth, the type and condition of the substrate, and the level of rain the surface
     is exposed to will all affect clean up time.  
     When Bio-Shield is used to maintain a previously treated surface that is starting to show the first signs of regrowth,
     clean-up is rapid, with noticeable improvement in 2 to 3 days in many situations.

   What is the best time to apply Bio-Shield?
     Any time of year is suitable provided the ambient temperature is above 100 Celsius. Warmer temperatures will increase
     the bio-cidal activity of Bio-Shield and lead to a faster clean-up. When using a garden sprayer to apply Bio-Shield, the 
     best application time is early morning because evaporation is reduced.
     The treated surface will stay wet for longer, providing a better clean-up.

   I collect rain water for drinking and household use from my roof, is Bio-Shield safe to use?
     Yes, Bio-Shield has been in commercial use for over 30 years, including on roofs that collect drinking water.
     The collection tank will need to be disconnected before application, and stay off for 2 to 4 weeks (including at least one
     day of rain) depending on the roof substrate.  Porous concrete roofs will take longer to flush clean than Coloursteel
     You will still be able to draw water from the tank for household use during this disconnection period.
     It is recommended that the tank is full before disconnection and to avoid treating the roof over the summer months in
     drier areas as there may not be enough rain to flush the roof and refill the tank after it is reconnected
     Before reconnecting the tank check the water coming off the roof during rain.  The water should have no smell or
     frothing. If smell or frothing is present, refrain from reconnecting the tank until the run-off water is clean.

  Will Bio-Shield clean my timber decks?
    Yes. Timber decks can take some extra work to cleanup, but if treated regularly every 6 to 12  months they will stay  
    Two to three coats are usually required; if the growth is heavy, agitating the wet deck with a yard broom and hose after
    2 to 3 months will assist in clean-up. This will return the deck to its natural timber colour. 
    After some weathering a hardwood deck will regain the silver colour.  Regular applications of Bio-Shield will keep it free
    of growth and help retain the silver weathered appearance.      

  Will Bio-Shield remove moss from my lawn?
     Yes, increase dilution rate to 1:30 = 33ml Bio-Shield to 1000ml water, and apply to the moss patches.
     The best time for application is in warmer weather so the moss will dry out after Bio-Shield application.
     After 3 to 4 weeks, rake out the dead moss and resow with grass seed. An application of lime and lawn fertiliser will
     help to promote healthy grass regrowth that will crowd out any resurgent moss.

  I don't want to use my credit card on-line, What can I do?
     Yes we can help with this. There are three options.
  1.    Call us at 0800 800 127 and your order can be manually processed over the phone with your credit card.
  2.    Call us on 0800 800 127 and we can issue an invoice which is payable by deposit at your local bank by      telephone or internet banking
  3. Select Direct Credit as the payment method.  When the order is confirmed you will receive an email with our bank account number, simply use you normal method of banking to transfer the payment to this account.

Discounts, special offers, new arrivals
Bio-Shield is a New Zealand owned company based in Auckland.
I have personally developed and used Bio-Shield 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 New Zealand.
We are committed to supplying our customers the best outdoor cleaning product and services at the best price, complimented with the best technical advice in New Zealand.

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