Limestone church


New member
Have a church covered in limestone . 3 yr old building . Dirt and black mold/mildew buildup . The building manager is worried about high pressure because he read somewhere on some website that high pressure is bad . I was planning on x-jetting with my m5 SH+lemonade +roof snot . Dwell about 15 minutes . Rinse with hot water high flow gpm. Bought some nozzles that will reduce pressure from 3500 to 1750. This is a huge church campus. Told him I would do a demo on a couple of pillars with limestone tops on them . Was thinking about hand pump spraying 12.5 % Sh with surfactant and low pressure rinse for show and to reduce customer anxiety . Should I dilute the hand pump pray or go hot and heavy to make it look real good and easy . When I do the whole building I was going to use about 3 gallons of 12.5% to 2 gallons of water. The manager knows I will bump up the pressure when I do the whole building to save time and get the job done but wants me to take it "Easy" for the demo because other people will be watching the demo . Any comments or concerns on this plan ?


New member
Make sure you pre wet a lot, limestone will soak up a lot o water and you don't want your chemicals below the surface. I would hit it a couple times before the demo point it out and how much time the pre wetting takes. Then pre wet again in the demo.
Obvious for many but just wanted to help with the demo plan.
Good luck.


New member
In my experience One Restore (acid) is way better product for limestone. I don't know why but sh seems to clean it up once, but the next time the stains come back deeper and more stubborn. However, working with One Restore might triple your costs.

Richard Ludlam

New member

We cleaned this monstrosity! All limestone.

Limestone is very porous and absorbent. Most building contractors will source all the limestone from a single quarry to get some uniformity in color...That said...every building with limestone facade will be slightly different. What cleaning procedure works on one, may be altogether different on the next. The Building Manager is correct, HIGH pressure will leave marks in the soft stone. We did a lot of testing prior to cleaning. The conclusion was that the best procedure was HIGH heat (185-200) @ 1350-1500 PSI with a 40* fan tip. The difficult areas we used stiff brushes to break loose the heavy build up. Go slow, take your time and back the nozzle of the surface.

We tested with many detergents and SH. Spent too much time pulling the detergents back out to make it workable.
I suggest you do some testing outside the presence of the BM prior to demo.

Good Luck!