I have been in the external cleaning business since November 2003.
All Exterior Cleaning has business insurance with Zurich which includes $5,000,000 General Liability Insurance. Plus, I have Workers Compensation Insurance & Income Protection Insurance for myself.
I do all of the work. I answer the phone, I do the free quotes & I do all the work. There are no sub-contractors or employees, it's just me.
I have a wide range of cleaning chemicals available for use from traditional products such as bleach (Sodium Hypochlorite), sugar soap and caustic oil removers, to high tech detergents, oil removers, graffiti removers and mould killers (biocides), plus natural enzyme and bacteria products for oil removal from ReKrete and United-Tech.
Pool chlorine (Sodium Hypochlorite solution) is about 10% concentrated, laundry bleach and bathroom mould cleaners are usually 4 or 5%, while my house washing solution is about 1%. This is just strong enough to kill the mould without harming any plants. If there are delicate plants near the house I can gently wet them with the garden hose before, during & after cleaning to ensure they are not damaged.
The best way to stop the mould from growing back it to kill it and wash everything away, this way there are no more mould spores & no dirt to stay moist and feed the mould. My cleaning solution (sodium hypochlorite & "sugar soap") and method (low-pressure water & hand brushing if needed) will leave the surface clean of dirt and mould spores, and therefore it stays clean compared to spraying "detergent" and water blasting.
I can apply a separate high-tech "anti-mould" treatment if wanted. I have researched "anti-mould" solutions but haven't found anything that is designed to work outdoors and withstand the sun & rain. At my home, I tested different products on some concrete and found that bleach (sodium hypochlorite) worked just as well as the other products (known as "biocides").
Very little water pressure is needed. I have a wide selection of extension lances and nozzles for the pressure washer which allows me to control the distance, angle and pressure of the water, and in some cases I just use the garden hose for washing & rinsing. If more pressure is needed, typically on painted weatherboards & cladding, and some-times gutters, I use brushes on extension handles (my longest is over 6m).