Hey guys and gals, I’d like to figure out what exactly this is on the bottom of a clients hardy board. I set the client’s expectations accordingly when i gave the estimate, but still want take care of it for him. It’s all along the bottom side of the house, but only on this side. My HW mix didn’t touch it. It rubs off like oxidation, but the house is only a few years old and really wasn’t dirty (besides the facia board).
After we were done, the homeowner grabbed a can of window cleaner and a hand towel and tried that (as I cringed) and all it did was take a little bit of paint off, but the white came back as it dried.
I don’t do a whole lot of hardyboard, so I’d like to see what I can learn from you all on this. Any ideas of how to remove it properly?
(I searched and came up empty in relation to hardyboard)
It’s not something you can clean…it’s imperfections in the paint. They need to call a painter, not a pressure washer.
Ive seen this too. It’ll be more noticeable after you wash it.
Ok thanks guys. I’ll let him know.
It looks like it may be rust actually.
Idk about acid on hardi board though
Actually yes it is rust. Try some Oxilic or if your feeling froggy pour muratic acid in a pump up sprayer and hit it. Let the homeowner know that you can’t guarantee the paint will not be affected
I thought about that too, and they have sprinklers on that side, but there are sprinkler heads on all sides.
Personally I wouldn’t worry about it…you set expectations. Move on, go make some money on a different job
Maybe overspray is only happening on that side. Look at the last board closest to the ground…that’s 100% rust .
Well the concrete
Only reason I want to try to fix it is its an older guy and he seemed lonely. Heck his house wasn’t even dirty… figured I’d give it a shot. Plus he’s only like 2 minutes from my house
Just seen you said it was rust.
I didn’t really think it was rust, mostly because it’s splotchy and only on one side. And its white
It’s some form of calcium deposits/rust.
A rust remover will work if your up to it. Might be easier to just move on though
Try some aluminum brightner (hydrofluric acid) or some f9 on it, just a small area out of the way. mix about 50-50, let dwell about 5min, rinse medium to lite pressure with like fan nozzle. If that doesn’t work, tell to call the painter.
Thanks Rick, appreciate it, And thanks everyone above as well
Any outcome yet?
Lost track of the post, my bad. I went back once after my full time job for a few minutes the other day. Didn’t have my chem tuff boxes with me, but the homeowner had tried some diluted white vinegar. When i got to looking closer I noticed small paint chips coming off in places (doubt it’s related to the vinegar). I recommended repaint. Got busy with the fam after that. When I get time I’m going to see what F9 will do, but I’m pretty sure he’s going to have the bottom few boards repainted.
The white stuff is weed killer and the “rust” is soil pigment 
