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How to Keep Moss from your Roof

Once you have scrapped the majority of moss from your roof (you will never be able to scrap 100% off due to the nooks and crannies of a tile) you will need to use a Biocide Chemical to treat the whole area from moss re-colonisation.

A Biocide is a chemical compound which is used to eliminate biological growths and remove biofilm staining. Most biofilms are a mix of symbiotic bacteria species which are algae, fungi, protozoa, yeasts and mould. The chemical we use is called GK Pro, which is only available to industry professionals and is highly ranked amongst roof cleaning professionals. It will kill 99.9% of bacterial growths within minutes of contact. We are registered with GK Pro to use their products.

GK Pro is free of solvents, bleaches and acids and does not have the chemical potential to interact with any substrate that isn't alive so it cannot alter the appearance, harm or discolour any surface. It is self-neutralising so it does not require rinsing off. GK Pro is a cationic surfactant, it punctures bacteria cell walls and prevents the bacteria cell from replicating, in effect killing it.

How it's applied

  1. Apply to saturation GK Pro begins to work immediately, green algae will be dead within minutes as will trentepohlia, a redish or red/orange-coloured algae, the beta carotene dye will wash away after the first rain.

  2. Filamentous fungi is seen as a thick black stain, often under coping or stone joints, the black is metabolised fungi acting as protection from the UV light for the live algae and bacteria beneath. These stains can take many months or up to a year to disappear.

  3. It may be considered expedient to vigorously brush in the GK Pro dilution this will help soften old and crusty metabolites and remove as much grime as possible, allowing this to dry back will mean the grime just sits on the surface area treated. In that case we would rinse the roof off with a hose. We would never use anything more than a hose and tap pressure (i.e. never use a pressure washer as this can invalidate your home insurance and undermine the integrity of your tiles - they are not designed to have high pressure washers used on them. It can take off some of the coating.

If you have anyone come to work on your roof and they mention using a Pressure Washer or are planning on walking on your tiles - please show them the door as you will see from number 3 above, it is completely against good practice to use such high pressures on your tiles.

We recommend GK Pro because it is reliable, predictable and we have had lots of positive feedback and happy customers. You can visit their website at

Destructive Roof Moss

Using a tower is necessary in taller properties and ensures safe working methods

Collect Debris prior to removal from site

Removal of 95% of Moss

Scaffold Tower to ensure no walking on tiles

Brushing in Biocide to effect the killing of moss spores and harmful bacteria and funghi

Biocide Treatment

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