What is the correct product to use in a pressure washer when cleaning mold off of exterior siding?

I've heard of bleach containing products and those without bleach, mainly TSP. Which cleans better, and is better for the landscape? and better for the paint and hardiplank? and cleans best.

20 Comments

Peace Painting Co., Inc. Alpharetta, GA

Lisa, we use chlorox outdoor bleach combined with Jomaps M1 house wash available at The Depot. Phosphates, the P in THP, actually promote mildew or algae growth, if any remains.
If it is a maintenance wash and not a before-painting-wash, use the mildest of concentrates (10% or less) because the same products that kill the mildew, break the paint down further. If you really have a mildew problem, then it is time to paint again.
Best, Charles

on Nov 03, 2011 · Like 0
RAGordy Decatur, GA

Bleach kills the mold/mildew, and it's what I used also--but I coupled it with liquid laundry detergent. Not sure if it was the right thing, but it did a great job. The only problem was the pressure washing part. I'm paying someone to do it the next time.

on Nov 03, 2011 · Like 0
Peace Painting Co., Inc. Alpharetta, GA

RA, you did the right thing putting soap in the bleach. The bubbles it makes helps the bleach to stay on the side of the house and work longer.
It can take years to learn how to pressure wash with the right equipment.
CP

on Nov 03, 2011 · Like 0
Karen G Palm Bay, FL

Anybody tried a product called 'wet and forget'? I would think products containing chlorine bleach is not too good for plants.

on Nov 03, 2011 · Like 0
Woodbridge Environmental ... Colonia, NJ

Any cleaning product that uses bleach to clean is not really that great of an idea to use on the lawns or plants. But these are the products that tend to work the best, So if your going to use these products, you need to.
1. pre-spray the plants with clear water before doing any work. Get the wet.
2. Cover the plants with light plastic, But do not leave on the plant for any extended period ...»
of time. Do not use black plastic. Only clear.
3. Rinse real well both the wall surface and once the plastic if off the ground and plants once again. This helps assure that any bleach that is on the ground or that has found its way onto the plant is washed away and diluted so not to harm the vegetation.

on Nov 04, 2011 · Like 1
Peace Painting Co., Inc. Alpharetta, GA

Thank you Woodbridge.
The only thing I could add to that excellent answer is that you can use white plastic to cover the plants so the sun's power does not burn them up under the plastic.
CP

on Nov 04, 2011 · Like 1
Ricardo B Alpine, TX

Even a homeowner pressure washer has sufficient PSI to remove mildew, mold and the sticky dust and dirt residue.
You don't need chemicals... you need patience and thoroughness. Folks... I'm plant, bush and environment friendly but before you think of me as a tree hugging nut, that's a no answer. Here's where I'm taking you. ...»

Look at all the pre-washing preparation you'd save and the expense of the chemicals and the expense of all that replacement ground cover and pretty spring things that are supposed to be green, not brown. It won't be if it dies but WHEN it dies out that your pocket-book with feel it.
I waited almost four years to pressure wash my new home with composite siding. The northeast siding made me shudder and the work ahead seemed daunting, at minimum. At 1300 PSI, the result was excellent... used no chemicals, no scrubbing and no bleach!

on Nov 04, 2011 · Like 1
HandyANDY Home Renovation... Marietta, GA

ahhh....have to disagree slightly with some of this. If you are just "cleaning" painted exterior siding or a vinyl, aluminum or other "permanent" finish siding, then try the Jomax house cleaning product. It is set up to screw onto a garden hose and you can usually use it from the ground or a step ladder. You can then hand clean any stubborn spots and call it a day;
If someone is prepping to repaint, the absolute best way to prep a house for painting is to ...»
hand wash the exterior with a mix of TSP, bleach and an additive we use and scrub with scrub brushes. Follow this application with a solid rinse...you can use a pressure washer with very low pressure but best to just use a hand sprayer to rinse everything off. Rinse any plants immediately. Pressure washing siding is best left to pro's although most of them get it wrong as well. We see tons of damaged siding as a result. Think about it....most people using a pressure washer are going to get a bunch of under the siding and into the wall cavity...where it will cause mold, at least in the metro Atlanta market
TSP actually cleans and kills mold...but just as important it "etches" the surface to be painted so the new coat of paint bonds better. Bleach doesn't kill mold...it knocks it down but doesn't kill. That's why you will sometimes see a recently painted house start to turn grey.....mold is anaerobic so when you paint over any of it, you just gave it a Hotel 6 to thrive in. Always a difference of opinion but that's what makes it fun!

on Jan 23, 2012 · Like 1
Rhino Shield By Georgia C... Lawrenceville, GA

Handy Andy, glad you typed all this out so I didn't have to. I was going to get started and then read thru the post and Thank goooooodness I saw yours.

on Feb 01, 2012 · Like 0
Peace Painting Co., Inc. Alpharetta, GA

Algae and mold thrive on the phosphates that are many times left behind with TSP.

on Feb 01, 2012 · Like 0
Rhino Shield By Georgia C... Lawrenceville, GA

Well I have to disagree, we have been using TSP/Bleach mixture for 10 years and haven't had a problem. Although we don't use regular paint, we are applying our mold and mildew resistant ceramic coating to houses.

on Feb 02, 2012 · Like 0
Peace Painting Co., Inc. Alpharetta, GA

That sounds good. If not thoroughly rinsed off, almost any kind of cleaning product can have an issue with the paint. The bleach can deplete the mildewcides in the paint, if some is left on the house; the very thing we are trying to prevent, more mildew!
CP

on Feb 02, 2012 · Like 0
HandyANDY Home Renovation... Marietta, GA

It's like anything else, if you know what you are doing...it's all in the mix. I developed my own mix for HandyANDY years ago...and it works like a charm. In 16 years of painting in and around metro Atlanta, I've never once had a mold or mildew issue on an exterior repaint. We only run a couple of paint crews now but years ago, we ran 10 to 12. We scaled it back as we mostly hand-painted and can't compete with spray pricing. Now, we have to offer both...hand & spray painting. As long ...»
as you rinse well, you'll never have a problem. The bigger danger cleaning houses is that most people use a high pressure pressure washer with a chemical injector to clean. That just causes a bunch of water to get into the wall cavity...where it certainly causes mold.
It's the season to start prepping for paint...we're already booking for spring & summer.

on Feb 03, 2012 · Like 0
Rhino Shield By Georgia C... Lawrenceville, GA

Yeah we are getting busy also! It's great to hear people are getting back to work.

on Feb 03, 2012 · Like 0
Terri J York, PA

Lisa, last I heard TSP was removed from the market. I have a vinyl sided hose and used a commercial power washer, detergent w/ bleach and scrub brush with stiff plastic ends. Rinsed and repeated. Rinsed and repeated until satisfied w/ the job. Then I gave it one final rinsing. I don't know where Rhino Shileld got their TSP from, but I know Lowe's discontinued it two years ago. We also covered bushes and close grass with cheap plastic to protect it, then just thru the plastic away.

on Feb 03, 2012 · Like 0
Rhino Shield By Georgia C... Lawrenceville, GA

You can still get in Home Depot and Lowes!

on Feb 03, 2012 · Like 1
Terri J York, PA

Thanks - I will try Lowe's again, but 2 years ago, they said it was pulled from the market. Maybe the gentleman working didn't know what I was talking about!!!

on Feb 03, 2012 · Like 0
Rhino Shield By Georgia C... Lawrenceville, GA

Here it is in the cleaning section, and you should be able to get in liquid or powder form.

on Feb 03, 2012 · Like 0
Peace Painting Co., Inc. Alpharetta, GA

We mix Chlorox Outdoor Bleach and Jomaps Roof and Deck Wash (sodium hypochlorite), both avail at the Depot

on Feb 03, 2012 · Like 0
Diane S Houston, TX

Sodium Hypochlorite is simply bleach which you can buy at any grocery store. Read the label....

on Feb 20, 2012 · Like 0