Mold is back

So our company has been pressure washing for about 7 years and we had a rather large building that we had to pressure wash with painted siding. I received an email from the manager about a 2 months later saying some mold returned in one spot and then a week later said that it all came back on one whole side which gets sun for maybe 30 percent of the day and is shaded the rest of the day with woods backing up to it. In all the years that we’ve been pressure washing I’ve never seen mold return so fast. I used a stronger house wash than normal . I’m wondering if I did something wrong any suggestions would be great.

Thanks Curtis, that’s the route I was planning. It came off super easy. It was really bad though. I probably could have gone hotter with my mix, so this next time I will.

If mold is coming back then the building has a moisture problem.

I have a few clients I clean windows for and every year I return to find the mold returned. It’s because they have heavy blinds and keep them close so moisture just sits there.

I’d refer them to a mold specialist for before re-cleaning.

You cannot control mold growth. A building wash is a not a permanent solution. Knock it out for free, tell them the situation and price them a quarterly cleaning if it persists. You cannot control the atmosphere. If your mix dwelled and removed it then it killed it, the environment dictates how quickly it returns. Not your hw strength.

what is your mix and technique for washing?

I downstream 12.5, water and simple cherry. I just visited the property. The mold has come back absolutely everywhere, like I never did a thing. Almost looks worse. Even came back on the front side where sun hits 70% of the day, but I would imagine if there are any moisture/mold issues it wouldn’t matter. This building is a retirement community; three stories and about 300’ long by 30’ deep. Its huge. To redo for free would be devastating because we also did the windows. Whole thing took 6 days for both services.

washing should have only taken half a day, max, your doing something wrong

Just a thought, but could the mold be systemic and your only killing the mold on the surface? I would tell them to call someone who can look behind the siding to make sure it isn’t there too.


I have never heard of something like this. I would jump on a couple of other sites, as you probably have, and make some phone calls to long time companies. Since you aren’t a newbie at this I would think you would have noticed an issue the following day when the windows were being cleaned. Where you on site the second day to see how it looked when completed?

Let us know what you find out. It would be nice to know as I haven’t seen or heard of this before either.

Haha. You’re funny.

So what I found out from talking with other pressure washing specific companies is that sometimes the paint prep or the paint itself is suspect. When I visited the complex the regional director was there also (I was a tad nervous), but he had told me that out of the 19 facilities in the state, all the ones with painted clapboard siding (all done approximately 5 years ago) had the same issue with mold returning on all the pressure washing contractors (they didn’t use us on all the properties). I’m going to redo a section just to make sure we weren’t “doing something wrong” as one fool mentioned, but they were already confident that the pressure washing contractors weren’t at fault. Thats good. To answer the question about how soon the mold returned, it wasn’t there even 2 weeks after the pressure washing because that’s is when the had us do the windows. The superintendent contacted us about 3 month later stating that some of the mold/mildew was back. When I looked at it today, approximately 4 months later, the entire building was completely covered. I’ve never seen the likes. Thanks for all the help. I’ll update as we move forward; this issue has prompted the company to consider repainting the buildings without vinyl siding.

In all seriousness though, we couldn’t move as fast as we wanted because of the balconies and various other factors because of the facility. It took longer than I planned because of those reasons. A half day though, yikes! You’d have to tell me how’d you do it. I’d love to know.

Everyone is amazing on the internet

you didnt mention balconies or other obstacles but you are still looking at one day of washing with two guys.

I am also amazing in person and maybe you could learn something if you had an open mind to.

I don’t have a problem learning from anyone.

Not painted but stained with a solid stain. Either the stain was bad, the prep was bad or the painter cut with something like linseed oil, otherwise known as mold food.

It’s the stain that’s causing stain.

I am glad that you are making headway with management.

As to time to pressure wash, no window cleaning, here is a picture of a building that is 180’ across the front, 40 ’ deep and 300’ of wall on the rear.

It took two guys (one of those guys is kind of old and decrepit and only helps when the real help doesn’t show up) 2 1/2 days to clean eight of these buildings. I know that many here, especially John and JC from Jersey, do a lot of communities like these and can probably knock them out in less time. We had issues on this job, the main one being that we hauled water for the majority of it. What a pain that was.

I have studied under JC, and although I would not call him amazing, we have been able to achieve amazing results by following some of the tips, tricks, and techniques that he has shared over the years.

ahh c’mon Tim, you know I’m amazing :cool:

This is fascinating. I agree that looking into the paint/stain is a good start. I’ve heard of decks doing this that have linseed oil in the stain. Also, whats above the siding? Maybe there is a gutter or roof system that is feeding active cultures on everything below. I wonder if there is any way to get a lab to look at this stuff under a microscope. Maybe it isn’t the cyanobacteria Gloeocapsa magma, like most mildew we run across is. Also I wonder if its possible for an irrigation system to get infected and spray spores everywhere.