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I am looking at a job with wood railings with some mold / mildew . Railings currently have and is getting a refresh solid color stain. New composite decking. This is a first time situation for me. Will using a cleaner with bleach on the railings discolor the composite? I plan to wet it down first but just dont want to take a chance. Looking to hear from someone who has done this.
 

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That's a great question. I wouldn't think so, but would certainly want to find out first..
@RH just built a composite deck. Maybe he knows!
 

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I am looking at a job with wood railings with some mold / mildew . Railings currently have and is getting a refresh solid color stain. New composite decking. This is a first time situation for me. Will using a cleaner with bleach on the railings discolor the composite? I plan to wet it down first but just dont want to take a chance. Looking to hear from someone who has done this.
Trex has a footnote on their cleaning instructions that states:
**Use of products containing bleach or acid will lighten the surface of Trex. Use in an inconspicuous area to determine whether you like the effect. Neither product will affect the structural integrity of Trex.
So I would say yes.
 

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I looked real quick and the only non-bleach mold killer I can find that is recommended for painted exterior wood is the Jomax House Cleaner and Mildew Killer. There are various others (Moldex, Concrobium Mold Control), but they are only recommended for hard, non-porous surfaces.
 

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There's nothing wrong with using a bleach-based cleaner on Trex; even the earliest iterations of it. The key is to pre-wet, keep it wet, and rinse thoroughly. As long as you're not trying to use a stronger concentration of straight bleach, (above 1%-ish), it's a non-issue. Biggest mistake is not pre-wetting the surface. Do that and you'll have no problems. If you want to go an even safer route, use a cleaner with sodium percarbonate in it instead, but those will require longer dwell times and multiple applications on the worst areas.
 

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Quick add-on question...

I don't do much exterior, so my experience on this is limited. However, I generally do a quick wet scrape with a wire brush for surface cleaning then sand down damaged areas to remove the rest.

Is this overkill or simply not as effective as other measures? I can't imagine it is something you want to do with pressure treated wood, but seems like it wouldn't be a health risk on standard planks.

Any advice is appreciated.
 

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Quick add-on question...

I don't do much exterior, so my experience on this is limited. However, I generally do a quick wet scrape with a wire brush for surface cleaning then sand down damaged areas to remove the rest.

Is this overkill or simply not as effective as other measures? I can't imagine it is something you want to do with pressure treated wood, but seems like it wouldn't be a health risk on standard planks.

Any advice is appreciated.
What surfaces are you talking about?
Vertical, or horizontal, like decks.
But regardless of that, many top coating products (especially for decks) warn very specifically about not using metal wire brushes,
because they can leave pieces of broken metal behind and they will rust under the top coat.
That's why stainless steel screws are the most proper screws to be used to secure deck boards.
Ceramic coated decks screws do eventually rust.
Maybe they were rust resistant years ago first when they came out and had thick ceramic coating on them, but these days they rust very fast in many cases.
Make sure you read very carefully data sheet of a particular product before using metal wire brushes to clean the surfaces you will be working on.
 

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I am looking at a job with wood railings with some mold / mildew . Railings currently have and is getting a refresh solid color stain. New composite decking. This is a first time situation for me. Will using a cleaner with bleach on the railings discolor the composite? I plan to wet it down first but just dont want to take a chance. Looking to hear from someone who has done this.
You didn't specified brand of that composite decking, there are several of them on the market.
I would find out the brand name of that particular composite decking and look into their data sheet for their recommendation how to properly clean it and what products to use.
If their data sheet is not addressing that to your satisfaction, I would contact them.
I would definitely not use anything with bleach in it no matter how much you pre-wet the deck, unless their data sheet says that is OK to use it.
 

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You didn't specified brand of that composite decking, there are several of them on the market.
I would find out the brand name of that particular composite decking and look into their data sheet for their recommendation how to properly clean it and what products to use.
If their data sheet is not addressing that to your satisfaction, I would contact them.
I would definitely not use anything with bleach in it no matter how much you pre-wet the deck, unless their data sheet says that is OK to use it.
It doesn't matter which composite decking, none will be damaged by using a cleaner with bleach in moderation as long as it pre-wet, kept wet, and rinsed thoroughly. None on the planet would be damaged. I wash anywhere from 70-150 composites a year. If you want to compose a reply to specifically disagree with me, you better make sure it's something you know about. This isn't it.
 

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I looked real quick and the only non-bleach mold killer I can find that is recommended for painted exterior wood is the Jomax House Cleaner and Mildew Killer. There are various others (Moldex, Concrobium Mold Control), but they are only recommended for hard, non-porous surfaces.
Jomax doesn't contain bleach but is a concentrate that you add bleach to. We use it all the time and mixing it to the recommended ratios has never affected a composite deck in a negative way.
 

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Jomax doesn't contain bleach but is a concentrate that you add bleach to. We use it all the time and mixing it to the recommended ratios has never affected a composite deck in a negative way.
#is a surfactant.

we stopped using Jomax after complaints of stubborn water spots left on windows, usually from the annoyed Spouse.
 

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Jomax doesn't contain bleach but is a concentrate that you add bleach to. We use it all the time and mixing it to the recommended ratios has never affected a composite deck in a negative way.
I somehow completely missed that, thanks! That explains how it works without containing bleach, because you add the bleach yourself.
 

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#is a surfactant.

we stopped using Jomax after complaints of stubborn water spots left on windows, usually from the annoyed Spouse.
I have seen that in the past and we avoid it by thoroughly rinsing all the windows once we are done with the side. We spray on the Jomax and bleach with a garden sprayer. I have the new Dewalt battery operated back pack sprayer. It is freaking awesome. Then we power wash. When we are done washing the side, we rinse everything from the ground making sure to hit every window so there is no chemical left behind. Windows look brand new. It probably takes an extra 10-15 mins per side, but we don't have to wash windows after the fact and everyone is happy.
 
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