Posting this on the private side...just wanted for you guys to hear my experience.
Custom homebuilder sends me lots of high $$$ jobs. This 12,000 SQF house needed a cleaning before turning over to the owners.
Siding is a pre-colored hardi-plank/hardi-shingle material. Home is on a dirt road, very soft/fine powdery stuff. Dirt would literally not detach without scrubbing. The trim was painted and had no problem getting the road grime of of it, however where the dust settled on the hardi-plank, nothing but agitating with a brush would remove it.
Here's what I tried:
1) Soft-Washing with soap & SH 2) Soft-Washing with a higher concentration of soap 3) Soft-Washing with Oxygenated bleach 4) Pressure washing at 2000 PSI 5) Pressure washing at 3000 PSI 6) Pressure washing at 4000 PSI 7) Manually scrubbing a soapy solution witha deck-brush and rinsing. ( Winner!!!!!!! )
Also, when wet on this green color the dust disappears, but when it dries an hour later, you realize your right back where you started.....
Finally got it done....learn from my mistakes!!!!!!!
Pressure washing alone on certain substraits does not always solve the problem no matter what materials you throw at them. I was just explaining that to a customer the other day. Sometimes a little agitation is needed to release the bond that is holding the dirt on.