The method for the removal of moss, algae or lichen from walls very much depends upon the the type of brick, age and general condition of the wall.
With all types of construction, the removal of moss, algae, lichen or just 'greening' is most important, not just for the appearance of the wall but to maintain its structural strength and lifespan. Brick, stone and block walls are porous and uneven surfaces provide the perfect surface for the moss, algae, lichen to happily grow. Unfortunately, this growth will, over a period of time, cause damage to the wall by loosening mortar and brickwork, all of which will eventually result in costly repairs.
A vast majority of this damage can be avoided by following some simple steps and undertaking a small amount of general maintenance:
The surface should be brushed to remove any loose growth, dirt and dust. The wall should then be inspected for damaged areas such as loose mortar, damaged bricks or loose stones and any remedial works undertaken.
If the wall is covered by trees, shrubs or plants, it may help to cut these back slightly to allow more light onto the surface, as this will allow the area to dry more quickly; dampness will encourage fresh growth of moss.
For a vast majority of surfaces, apart from soft stone such as sandstone, the best method for treating a wall with lichen coverage is to spray the area with RAPID MOSS & ALGAE KILLER - Batiface. This kills the growth on contact and should be left on the surface for 30-60 minutes. After this time, the area should be washed with either a hosepipe and brush or, ideally, a SMALL pressure washer. The advantage of using a pressure washer is that it will not only rinse away the product but also remove the dead growth from the surface.
Our comprehensive range of sprayers can be found HERE.
Once the treated area is dry, we advise the application of CONCENTRATED MOSS & ALGAE KILLER - Baticlean CR. It is impossible to remove all of the spores without a fungicide (you can't see them!) and a second treatment using Baticlean CR will ensure that all remaining moss and spores are dead. Without rinsing, the product then stays on the surface to inhibit re-growth.
If the wall suffers from 'greening' then, on a dry day and a dry surface, apply a coat of BATICLEAN CR. Baticlean CR will kill the growth and spores and is designed to be left upon the surface where it can inhibit re-growth. Please remember that Baticlean CR should only be sprayed on to a DRY surface.
After both of these treatments, you can apply a water repellent sealer to the surface. This will provide long term protection to the area and keep fresh growth at bay for up to 10 years, as well as protecting against water ingress (which will reduce the effect of frost on both the bricks and mortar) and against dirt and general weathering. For these surfaces we recommend ROOF & WALL SEALER - Hydrosil BS. This is water based and soaks into the surface but still allows it to breathe.