Roof cleaning

Roof cleaning

The first step will consist in removing the moss from the roof surface. This is generally the labour intensive part of roof cleaning and requires protecting the gutter and collecting the fallen moss. The tools are scraper & brush. If the green blanket is dense and thick a compressed air gun connected to an 100 cfm air compressor can considerably reduce time on site.

Lichen can be left to themselves or lightly brushed if the crust ring is old. No chemical will dissolve the crust and the best course of action is to soak them on a dry day with the APC biocide. The dead crust will saturate, desiccate and sometimes freeze in weather cycle and fall when ready. This is usually observable within a few weeks of the application but a few lichen may be seen much later. The species with a thin almost flush crust tend to multiply in a snow of small dots and etch themselves into concrete. They take the longest to vanish and should ideally be treated before the roof is too contaminated.

The ACP biocide is applied diluted in a hand sprayer for small work and through a dosing unit for larger undertakings. The flow rate measured on this video is 5.4 litres per minute using a large bore fan spray tip.

Small moss incrustations and thallus will wither and fall. The black layer is no longer replenished and thins down in the weather. During a wet season the progress begins to be observable within 2 weeks but can take longer. The dark overlay has, in normal circumstances substantially disappeared 3 months after the treatment.

On concrete the saturation rate is approximately 1 litre per m2. A good saturation will kill the reproductive cycles and give good durability to the treatment.

Apply on a bone dry substrate. Never wet the tile before applying the ACP biocide.

Before Roof CleaningAfter Roof Cleaning
Thatch Roof Cleaning using ACP biocide
Area per litre of ACP biocide concentrate Concrete tiles Clay tiles Natural slates Thatch Cementitious agricultural sheeting
Dilution rate 1 to 20 1 to 20 1 to 20 1 to 30 1 to 20
Visual guide Saturation Saturation No excessive dribbling at eaves Saturation
Guide application rate of the mix 0.8 litre/m2 = 1.2 m2/litre 0.5 litre/m2 = 2 m2/litre 0.33 litre/m2 = 3 m2/litre 2 litre/m2 = 0.5 m2/litre 0.66 litre/m2 = 1.5 m2/litre
Area for 5 litres of ACP biocide concentrate 120 m2 200 m2 300 m2 75 m2 150 m2

Clay tiles are less absorbent and natural slates not at all. The operator will begin the treatment at eaves and progress upwards with a smaller nozzle pushing the mix into laps and bonds and avoiding excessive dribbling into the gutter.

Natural slates are brushed when a particular brown filamentous growth is present in patches (generally in coastal areas). It adheres to the slate and needs softening by brush on the day.

Large slate roofs will reach high temperatures in summer and cook a heavy biofilm into a hard adhesive one. The hardened film is removed with medium/high pressure water.

The Algoclear Cleaning Process has been tested for the maintenance of thatch to the satisfaction of the Society of Master Thatchers. Removing growth from thatch is a skill best left to professional thatchers.