Painted Houses, HardiePlank, Colors -etc

Hi all.
I’ve been searching here and PTState for days now scouring for detailed info on cleaning any kind of painted surface. Haven’t been at the whole pressure washing biz for very long and a month or two ago I left a SERIOUS streak on a homeowner’s joint. Luckily she still gave me a five star review, but on the inside - I feel like a rotten contractor… Driving past her home after finishing and seeing that streak haunts me still. So discolored. Right down from the corner of a window.

ANYWAYS. I have a gig at one of the nicest homes I’ve quoted all season tomorrow. The gig tomorrow is a huge cream colored hardieplank exterior home. Has like 10 different sides and real ■■■ black painted shuttered windows that open and close. I’ll attach some photos. I am so paranoid and worried about this gig that I’m staying up at night thinking about it.

Here’s what I’m working with.

  • 4gpm/4000psi PW’er
  • X-Jet M5 system (no proportioner tip installed at the moment)


  • 1 gallon 12.5%SH (I’m scared to go any higher)
  • 10oz Simple Cherry
  • 4 gallons water

Here are the things I’ve learned from searching, just so y’all know where I’m at and so this doesn’t feel like a sh1tpost - maybe this will help out anybody else in my situation. Let me know if any of these seem like they would hurt me.

  • Pre-wet surfaces before applying soap.
  • Short dwell time.
  • Rinse windows first.
  • Use less SH in mix than usual. (I usually go 1.5 to 2 gallons).

Any specifics on these tips? Any more tips? For the unusual sections of the home that jut out, how should I handle those? Whats the lowest amount of SH I can use that will still clean up these whites? Anybody wanna call me stupid or a big dummy? Plz help.

Old time exterior painters often use a TSP based solution (not sure of the mix ratio) to clean painted surfaces before repainting.

If just cleaning, a light sodium hypochlorite (bleach) solution, 1.5 - 2% concentration on the wood with a bit of soap and surfactant for “cling” will kill any mold/mildew and remove normal dirt. Rinse at low pressure. At that mix, no need to pre-wet.