Austin stone house mold removal

Hey everyone I’ve been asking around about this house that is completely made of Austin Stone the picture I’m showing you is obviously older has a bunch of black algae on it now. My question is the proper way to attack this job. I talk to the guys at Powerwash.com and they told me to use my Diaphragm pump and do 40% SH 60% water. I’m just really worried about all these windows and plants around the front of the house with that hot of a mix. Any suggestions? My thoughts are to soak the hell out of the windows right before and after the application and plants as well. Thanks for your help in advance

Get updated pictures. If you’re not busy just try a small test spot. See what % you will need. Remember you can always go stronger it’s not a good idea to go the other way.

I did a little reading (having lived in TX) and I guess you need to find out if this is actual limestone or the copycat cement stuff.

I’ve done a ton of this (200,000 sq ft this year alone).

  1. SH is most likely going to add a mild orange hue to the finished product. My understanding is in the stone are ironites that react to the SH causing the slight organish color. You need to treat the entire wall and not spot clean to make it all blend together. I have not had a single homeowner / property owner comment on the hue, but it is something I see.
  2. Yes - it takes a strong mix. Usually, you will pressure wash with medium pressure to knock off the surface mold/algae. After that the stones will have a grayish color as the mold/algae is inside the pores of the stone. It is a process of applying chem, keeping wet and letting the chem soak in enough to kill the mold/algae. Be prepared for several (sometimes 3,4 or even 5 applications). Can be very time consuming. You are not washing vinyl here. Sometimes on tough spots, I spray chem and keep apply chem to ensure it stays wet and soaks in for upto 20 min dwell. I almost feel that apply to dry stone is better as you want the stone to soak it in unlike most substrates where you only want the chem on the surface.
  3. I have used a 2.2 gpm 12 v for chem application as well as pump-ups when I want to control spray more.
  4. You will be on a ladder for sure - you will not be able to do the normal DS, dwell and rinse like a normal housewash.
  5. You might consider Agent Halt (chlorine neutralizer) since you will be using a hot mix.
  6. You can use a product from Prosoco in place of SH called ReKlaim. It is not cheap and is just as toxic (it is basically hydrogen peroxide and sodium hydroxide). It does not bring out the orange like SH, but it is very expensive compared to SH and I don’t think average homeowner would pay the increased cost. It would work well in other situations such as heritage restoration or such.
  7. Because of the hot mix, you might want to add Arm and Hammer laundry soap as a scent masker along with your Elemonator. It will also help with the cling on the stone.

Here is a link to a post I made about a baseball stadium job I did that was covered in this stone.

You might notice in the video the orangish color I reference above. Some areas not at all, but others, at least to me, I see it. I also speculate that with mold, it is trapping water at/below the surface which might be interacting with the ironites in the stone causing the rust orange and that once cleaned the color is revealed. It is absolutely noticeable when I see someone clean this stone and only spot clean the mold spots.
Good Luck!

7 Likes

Wow! Thanks for the great advice, great job on the stadium it looks amazing! I guess I cannot charge a standard house wash feet for this looks like it’s gonna take me a few more hours to get the job done. Quick question you don’t tell the customers upfront about the orange hue? I almost want to say something to be completely transparent.

On the aspect of informing home owners. I have only done a couple of homes (most of my work in general is commercial) and they were so bad, having it clean with a slight orange hue was a vast improvement that I did not tell them. If you choose to, in my experience home owners don’t like to hear bleach. I use terms Sodium Hypoclorite or chlorine based algaecide. It is totally up to you on how you want to handle that. Also in terms of price, good luck. The fact these homes take 2-3 times as long is a hard selling point for double or triple regular house wash price. You might be able to increase some, but not in direct relation to the additional time. Customers won’t bite or at least ones that I tried that one didn’t.
One thing I failed to mention - once you “clean” the entire side of a home, you can then spot apply chem without resulting in spots of a different color hue. Not all stones will do it either. Austin stone is a variant of limestone, and as a natural rock, inconsistencies exist. I have washed some walls where no color changed occurred at all.
If the home has never been cleaned, you will want to upsell window cleaning. Something about this Austin stone, even with rain, until you clean it will some light pressure it stores tons of “dust”. Your first rinse might be a milky mess and no matter how much you rinse the windows, they will look fairly bad when you are done.

1 Like