Questions About Mildew & Stain

MOTG1

New member
Is it possible for mildew (or other spore) to get trapped between 2 applications of oil-based stain and grow?

I put down a stain last year, turned out great. This spring, customer asked for a new coat, and we applied it. 2 weeks later, everything looked great! About 2 months later, there is black stuff all over the deck.

I haven't treated it yet, but spoke with the product distributor and his opinion was that spores got trapped between the coats and I may need to strip.

Looking for advice. Thanks.
 
Marc,

The quick answer is absolutely yes! Most stains and sealers will last approximately 2 years before they need maintenance. What you performed would be considered a maintenance clean and application. Typically we clean these with a solution that has a bleach content to it to kill mold and mildew spores prior to re-coating. If this is not done or done incorrectly then you will indeed trap the mold and mildew between layers and it will grow like wildfire. What we do is get a deck to where we can maintain it the first time out. Then we apply a 2 coat application to all surfaces (oils should be applied wet-on-wet) and then our maintenance involves a cleaning and then a 2 coat application on horizontals and a 1 coat application on verticals. If a customer wants it done every year you should probably do 1 coat on the floor and skip every other year on verticals to keep it even. Now the issue of fixing what you have, you should probably strip it and then brighten it and re-coat. I say that because of the separate coats and the current mold issue and being able to fix the problem correctly. If I were to bid this job I would give a price to strip and brighten to correct it. On another note, we restored a Redwood Sided House earlier this year with the same problem. I felt bad for the homeowner but not only did they trap the mold and mildew in but they also put the stain on wet-on-dry and it was shiny in some areas as well. When they "cleaned" the siding it was just water and pressure so they did not kill any mold and mildew and also scarred up the wood. Unfortunately it looks like a learning lesson on this one. Let us know if you need any other help.
 
Great, Everett!

Thanks for the information and fast reply.

I did clean the deck prior to staining, but it was during the early spring when we had a lot of wet weather, so there were likely a ton of spores. It was also during a heavy pollen (goes by like yellow clouds here), so maybe something settled into the stain while it was curing?

Anyway, it's likely that the strip, neutralize, and stain is the answer. I'll test a spot with bleach just to see what happens.

Thanks again!
 
Marc,

The quick answer is absolutely yes! Most stains and sealers will last approximately 2 years before they need maintenance. What you performed would be considered a maintenance clean and application. Typically we clean these with a solution that has a bleach content to it to kill mold and mildew spores prior to re-coating. If this is not done or done incorrectly then you will indeed trap the mold and mildew between layers and it will grow like wildfire. What we do is get a deck to where we can maintain it the first time out. Then we apply a 2 coat application to all surfaces (oils should be applied wet-on-wet) and then our maintenance involves a cleaning and then a 2 coat application on horizontals and a 1 coat application on verticals. If a customer wants it done every year you should probably do 1 coat on the floor and skip every other year on verticals to keep it even. Now the issue of fixing what you have, you should probably strip it and then brighten it and re-coat. I say that because of the separate coats and the current mold issue and being able to fix the problem correctly. If I were to bid this job I would give a price to strip and brighten to correct it. On another note, we restored a Redwood Sided House earlier this year with the same problem. I felt bad for the homeowner but not only did they trap the mold and mildew in but they also put the stain on wet-on-dry and it was shiny in some areas as well. When they "cleaned" the siding it was just water and pressure so they did not kill any mold and mildew and also scarred up the wood. Unfortunately it looks like a learning lesson on this one. Let us know if you need any other help.

Great wood restoration educating right here on the pressure washing institute with industry experts.
Thank again Everett for helping


Text me for info on Milwaukee event. 480-522-5227
 
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I have also seen it in sealers, stains and paint. If it is not killed and removed properly it will come through the surface and ruin the job no matter what is says on the container and no matter what company makes the sealer stain or paint.

I have seen houses and buildings painted that were ruined by the incompetent painters that did not kill the mold, algae or mildew before painting and letting the surface dry out before painting. The painters try to blame the product and say how many years they have been painting but years does not mean anything these days as so many of them take shortcuts and don't do a good job then the paint manufacturer shows how the mold, mildew or algae was not treated or killed before painting and how it is the painter's fault and most of those guys in this area don't have insurance to cover their mistakes. I hear about this all the time down here, so many painters but not a lot of common sense or proper painting knowledge to do the job the right way.
 
Did you strip the deck down to bare wood when you did the first application last year? As Everett said it definitely can be trapped between the two coats but if the deck was not stripped initially you may be dealing with a stain prior to your own two coats causing problems
 
Yeah, I stripped and sanded the deck last year. There were no problems, just that the stain is a clear and it had faded in some places and homeowner wanted a new coat. So....

This year I cleaned the deck with bleach, rinsed, neutralized, left and waited half a day for it to dry, and applied the stain. We had a very wet winter and spring, and although it was a nice day, the pollen was floating by like yellow clouds. I'm guessing that there were enough spores floating around that they settled between the time the deck was washed and the stain cured. If not that, then I don't know what happened.

Well I went back and hit the deck with bleach and it wiped out the stuff almost instantly. I applied bleach and rinsed twice - which also pulled some of the oil stain out too - neutralized, and stained. Came out great.
 
Well I went back and hit the deck with bleach and it wiped out the stuff almost instantly. I applied bleach and rinsed twice - which also pulled some of the oil stain out too - neutralized, and stained. Came out great.


Sweet BDA strikes again.....cool glad it worked out for you!
 
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