Any advice on this block building


Normally, just pressure washer without chemical would remove this. I’m at a loss. I’m sure this is newbie material but any advice on chemicals to use or what the stain is would be appreciated. Thanks.


Oops thought i seen oxidation running down from the roof…




You got a closeup pic? Hard to tell what’s on from the one you posted.


I zoomed in and it appears to be very light mould.

Where I live, there are three main moulds that I deal with.

Green - early stages, very easy to remove.

Black - the green turns black after a while and requires more chemical, but rarely pressure.

Actual growth - such as lichen and there’s a red/orange build up one too, it’s raised and takes much, much more chemical and pressure to remove.

What I see is green - very easy to remove with SH/Sodium Hypochlorite/Bleach and some soap of your choice.

The dwell time will be minimal and it would probably be gone by the time you reached the end of the wall.



I will be trying out SH today. Here are some more pics of the wall.

Should below freezing temps (25-30 F) be a concern when using SH?

Thanks guys


Yes. …


Just use a higher concentration and longer dwell time


If I go 1 part SH to 4 parts water, is that a decent start or even higher concentration?


I don’t know what you are applying with. When it is before 30 we ds straight SH