First we'll pressure wash the outer areas with a turbo lance and then focus our attention on the main patio surface. Very often we'll use a rotary flat surface cleaner to get this part of the job done quickly and effectively.
A regular power wash is environmentally friendly, using only normal tap water, applied at very high pressure. Optionally, for some organic stains we may also need to use biocide chemical treatments.
As well as weeds and moss, we find that a very common problem with patios is Black Lichen; often called blackspot.
A blackspot infestation appears as unsightly black splodges on the surface and it can not be removed with pressure washing alone. It's especially difficult to remove from expensive Indian sandstone, York stone slabs and block paving.
A deep clean with a solution containing a high concentration of sodium hypochlorite is the only thing that will remove blackspot on the day. This is a strong chemical and we need to use PPE when applying it. That said, it biodegrades very quickly and does not pose a lasting hazard. It's safe for pets and children once it has been rinsed off and has dried out.
The cleaning process is similar for most patio surfaces, although we use lower pressure when working on sandstone or limestone flags. Likewise with crazing paving and anything else with mortar or pointing.
If the patio is made of block paving we'll return on a dry day to re-sand the blocks. This is an essential part of the process because it inhibits weeds, secures the blocks in position and prevents any movement.
If there are deep rooted weeds, it's best to treat them a week or two before pressure washing. You can easily do this yourself with a glycophosphate weed killer such as Roundup, or for we can do this for you.