Skip to content
Call us on (02) 9986 2126
Call us on (02) 9986 2126
Lichen or black mould on your roof?

Lichen or black mould on your roof?

Wet & Forget is non-acidic, non-caustic and contains no bleach and will not damage any surface.

Here are a few tips for when you apply Wet & Forget to your roof to get rid of lichen and/or black mould:


For an average 3 bedroom tile roof with lichen you would require 3 x 5 litre packs depending on the total area covered with lichen.

For best results mix the Wet & Forget and spot spray the lichen, leave for 10-15 minutes and then respray the lichen and the entire roof to ensure the lichen absorbs the Wet & Forget thoroughly. The first application is to dissolve the waxy surface. The 2nd spray will then penetrate the lichen.

Black Mould

The average 3 bedroom tile roof is approx 150sq mts, but because of the undulations of the tile profile the actual area is a lot bigger. Therefore an average tile/concrete roof would require 2 x 5 litre packs, depending on how porous the surface is and how much biological growth is present. For green moss and black mould one application is normally sufficient. 

Tank Water

If you are on tank water disconnect the water supply to your tank for at least the first 10mm of rain or 2 good downpours to avoid any chance of contamination. Check before reconnecting that the water flowing onto the ground, when raining is not foaming.


Simply dilute as per instructions on the bottle into a household garden sprayer or backpack sprayer.

If badly contaminated, apply a second application one month after the first.

Wet & Forget is best applied in overcast dry conditions to avoid rapid evaporation.  

Spray the affected area to the point of saturation. DO NOT hose off.

DO NOT apply if rain is expected within 12 hours.

Reaction Time

The time it takes for an infested surface to become clean depends on the type and intensity of biological growth.

Black mould and Lichen will take 6-8 months and badly contaminated surfaces can take 12 months.   


Here at Wet & Forget we always promote safety first so always ensure that you are safely harnessed to your roof and never walk on the section you have just sprayed as it will be slippery until it is dry.


Wet & Forget is okay to use around plants provided certain protective steps are taken. When spraying the product near plants, make sure to either cover them with a tarpaulin (or something similar) or alternatively, wash the plants down with water before and after applying the product nearby. The leaves of the plant may experience a slight discolouration or spot burn if they come into contact with the product for an extended period.

To shop or read about Wet & Forget, click here.


Previous article Do you have interior mould or mildew?
Next article Alternative Uses for Shower Witch
Back to top