Pressure washing the surface of the patio is a simple and often very effective option. However it does not prevent the growth of such stains and is generally a messy and
often time consuming process.
Moss Killer Chemicals
One little known trick to easily remove the stains is to apply a fungcide (also known as
a moss killer chemical) directly to the surface without any wire brushing or pressure washing.
For this method to be effective the following conditions must first be met:
- Chemical must be high strength - not your usual garden centre type
- Rain should not be forecast within the following 48 hours
- Chemical should be applied liberally
The following is also advised:
- Keep pets and children away from the patio for at least 48 hours after application - use a cover over patio if you wish
- Avoid run off into streams/ponds etc as these chemicals are extremely dangerous to aquatic life
Because the black marks on the patio are organic it will take some time before you see the effects but gradually the patio will brighten up and because
the chemicals soak into the porous concrete slabs they will offer protection for up to a year - considering re applying each year for continous protection.