Mosses and lichens grow in damp conditions. Moss itself is a plant, while lichen conisist of a fungus and a photosyntheizing plant living together. When leaves and other material collect on your roof, a perfect bed is formed for moss and lichens to grow. You can remove moss and lichens from your roof by using vinegar as a environmentally friendly weedkiller.
Clean up any organic matter on the roof such as twigs, leaves or other debris. In addition to rotting and possibly damaging your roof, organic material is one of the chief growing places of both moss and lichen.
Use a stiff brush, such as a pushbroom, to scrape away any stubborn mould or lichen patches still remaining. Start at the top of the roof and work your way toward the eaves. Stay well away from the edge of the roof.
Set up a tall ladder next to the house. Use the brush to get rid of any moss around the roof edges. Work your way around the house.
Pour distilled white vinegar into a bucket. The vinegar should be labelled with its acetic acid strength, which shouldn't be more than 5 per cent. Add 30 ml (1 fl oz) of washing up liquid to help the vinegar cling to the moss and lichens. Pour the mixture into the spray bottle.
Apply the vinegar to the moss and lichens on the roof with the spray bottle. Get off the roof and apply the vinegar to the moss and lichens around the edge.
Wait for the vinegar to kill off the moss and lichens. This generally takes a couple of days.
Use the brush to remove the dead lichens and moss.
Rinse off the roof with a garden hose and sprayer.
There are many recipes for the mixture of vinegar and washing up liquid. You may need to try several combinations to find one that works right for you.
Use harnesses and other safety equipment when working on the roof.