About Your Roof: 


Gerard and Decrabond Roofs

Algae and Lichens will grow into the decorative stone chip coating on your roof, peeling it back to bare steel. Regular cleaning will extend the roofs service life and improves the appearance of your roof and your home.

How to Clean & Maintain Gerard & Decrabond Roofs

Your new stone chip coated roof will resist algae and lichen growths for 3 to 5 years under normal conditions.  Algae and lichen will then begin to naturally grow when conditions are right – temperate climate with regular rainfall and a source of spores.

These growths not only look unsightly on your roof – they will cause severe damage to the high quality stone chip coating, peeling it back to bare steel.

Bio-Shield will clean algae and lichens and maintain a chip-coated roof without harsh chemicals, water blast cleaning or washing down, – its a simple, quick and no mess application.

The Cleaning Process
Bio-Shield is highly effective for cleaning stone chip coated roofs and does not require specific formulation or application methods to ensure an effective kill of lichens and black algae.
We will apply Bio-Shield to your roof to kill the moss, algae and lichens, within 2 to 3 hours.
You will notice distinct colour changes in the lichens over the next few weeks as the dead growths start to breakdown.
After 2 to 3 months, the cleaning process will be more visible, as rainfall and wind begin to remove the dead growths, revealing more and more of your roofs original stone chip finish.
After 12 months, the roof will be fully clean and stay clean for up to 2 years.

Maintain your roof with Bio-Shield
We recommend re- application of Bio-Shield every 2 to 3 years, to keep the roof clean and protected.
With regular applications of Bio-Shield, algae or lichen spores and light re-growths will be quickly removed, and the roof will stay clean for another 2 to 3 years.

Water Blast / Pressure Cleaning:
Any stone chip coated roof should only be water blast cleaned as preparation for repainting, never to remove lichen growths. 

2 Year Guarantee
Bio-Shield applications are covered by a written 2 Year Guarantee

Expert Gerard and Decrabond Roof Cleaning

Roof Cleaning Ltd are genuine specialists in Bio-Shield roof cleaning, with over 37 years experience and more than 9700 roofs cleaned and treated with Bio-Shield®. Expert Application, Proven Performance, Reliable Results

Yes, Bio-Shield has been used commercially and safely for over 37 years and on more than 9700 roofs in New Zealand. It is not acidic, not a bleach and not abrasive like pressure washing, so won't cause any damage to the protective and decorative coating, pointing mortar, skylights, vents,gutters, solar panels or other fittings and fixtures commonly found on roofs.

 A general guideline for the clean up time after initial Bio-Shield application would be 3 months and up to 12 months, if the growths are heavy and well established on the roof.
Other factors that affect clean up times is the pitch of the roof and how much rain falls on the roof once the dead growths have begun to break down.

 Roofs that have previously been cleaned with Bio-Shield and is having a 2 or 3 yearly maintenance treatment can clean up in a matter of weeks if the growths are light.

Yes, Bio-Shield is water based, water soluble and bio-degradable so it is safe to use on roofs that collect drinking water. The storage tank will be disconnected before application and can be reconnected after a minimum of 3 to 4 weeks and at least one day of rain has flushed the roof clear of Bio-Shield residue.

A diverter can be installed on the tank inlet pipe, on above ground tanks to isolate the water tank form the roof and make reconnection and any future disconnections a 15 second task. No need to remove down pipes or fit expensive and ineffective diverters to the down pipes

We do not recommended cleaning a roof over the summer months, from January to March , in drier areas as there may not be enough rain to flush the roof and refill the tank after it is reconnected.

Gerrard and Decrabond tile roofs should be treated every 2 to 3 years to maintain them in a clean condition. Regular treatments will help to preserve the factory stone chip coating in good condition. Roofs that have been re-coated or resurfaced with an acrylic coating system can stay clean for up to 4 years, depending on the quaity of the coating

The micro climate around a roof will have a large influence on timing between the maintenance treatments.

If there are trees near the roof, the roof is steep pitched or birds habitually use the roof to rest or nest, annual or 2 yearly treatments may be required to keep the roof clean.

Unfortunately some applications by companies that are not specialists in roof cleaning, for example house wash, gutter cleaners or handymen, are not being done correctly and leaving a patchy clean up from incorrect or incomplete application.
Bio-Shield gives a faster and superior clean up and roofs treated with Bio-Shield are guaranteed to clean up.

Bio-Shield can not kill plants, it is a surface santizer, not a systemic garden spray.
It can safely be used on lawns to kill moss and on tree trunks and branches to kill lichen.
In sunny conditions, some delicate leaved plants can get spotting on leaves from contact with Bio-Shield so any affected plants are hosed down after the application.

Edible plants near the roof are always hosed down after the application.
Bio-Shield is fully bio-degradable when in contact with organic matter and soil

The active ingredient in Bio-Shield has been safely and continuously used in the the food industry, in hospitals, veterinary clinics and zoos as a hard surface sanitiser for over 60 years.

The only precautions we take are to move feed bowls and toys away from the roof, and flush them out after the application is complete.

When Bio-Shield is applied to any roof we provide a written 2 year guarantee on the effectiveness of the application.

While there are conditions to this warranty, these are common across all roof treatments as they relate to the  situation, pitch and conditions around the roof, not the quality of the application.

You should be aware of the limitations that the above conditions - Read More