[timglaze]

Any advice on method and/or chemicals needed to clean these walls would be greatly appreciated. Would softwashing be the preferred method to pressure washing?

[Smurf]

That to me looks like a grade 1 or maybe 2 listed building with heritage leaded glass.
I would stay well clear myself as I don't get involved in listed buiding cleaning as is a specalist job and would certainly not use a pressure washer on it.

Even cleaning stonework etc the owner of a listed building needs to seek consent and abide by the approved methods of cleaning or can face prosecution.
 

[chris scott]

Hydrofluoric acid
Don'ty  full clean  it …it will look terrible.
http://www.cleaning-service.uk.com/listed-building-cleaning-in-lancashire/

[mop-n-scrim]

After checking any restrictions, if clear to go ahead, then I would use AlgoClear Pro, as it wouldnt affect anything apart from the gren algae.
It takes very little effort to clean, and continues to protect.

I only managed to get 70% off softwashing, but it continued to work & took the remainder off within 2 weeks, without having to further wash.



Ray

[Smurf]

That's a slow way to clean render as using a hypo mix instead would have done an instant job.

Regards to listed building then algoclear is probably not the best option on stone as you want the green algae gone but as Chris mentioned you don't want it looking too clean or will look very odd. Algoclear can still have a detrimental effect on soft metals like lead so would need to be used with caution especially around stone window frames with heritage leaded glass.

[Aqua Power Solutions]

I presume you want to remove the algae then low pressure and heat ..... Job done !

Ed