Update for 2019: My Deck Stain Turned Black
We appreciate when people write in and ask for advice when something goes wrong during their deck staining projects. Today we talk about what causes your deck stain to turn black after a year or two and what to do to get rid of the problem. We appreciate your input, so feel free to leave a comment below with pictures of your deck stain projects.
Black Deck Stain
Why Did Your Deck Stain Turn Black?
Many things can happen to a deck stain when it is not applied or maintained properly. The biggest reason for a deck stain turning black is mildew. All wood surfaces need to be cleaned correctly prior to staining. The use of a quality wood cleaner and pressure washer or scrub brush is necessary to remove all the contaminants like dirt, grime, mold, mildew, and graying.
When contaminants are left in the wood pores and stain is applied a whole host of problems can occur. Mildew can begin to grow underneath the deck stain, which causes discoloring. This can also lead to rot and decay because if there is mildew there is also moisture present.
Another reason your deck stain turned black can be from using an inferior stain. Cheap quality deck stains do not contain the mildewcides and inhibitors that more quality deck stains have. The mildew or black discoloration can occur on top of poor quality stains. Some low-quality deck stains can even be the cause of mildew infiltration. Some cheaper deck stains can actually cause mildew to grow in certain conditions.
To cure a deck that has turned black you will need to strip the wood using a quality wood deck stain stripper or wood deck cleaner. Remove all the old existing deck stain along with any graying, mildew, and other contaminants. Wash the deck several times if need be. Once all the wood is clean and allowed to dry for several days, apply a quality deck stain that contains mildewcides and mold/mildew inhibitors so the darkening of the stain does not reoccur. Proper maintenance should include a light wash every couple of years followed by a recoat of the same quality deck stain.
I had my deck sanded to the bare wood. Then I used a brightener twice and let it dry completely. After mucho research, I chose the Armstrong Clark stain and applied one coat which looked okay. It dried and after a couple of weeks I applied a 2nd coat. The deck has turned black from what I suppose is mildew even though this stain supposedly has a mildewcide. I have not idea what I could have done differently. I was very careful to follow directions for each step. I’m disgusted.
It may not be the stain’s fault but improper prep and over application. Basically, if the stain cannot so into the wood it can have issues curring correctly. This can lead to dirt and grime collection or even mildew. Sanding reduces stain absorption and adding the second coat two weeks later will enhance this issue.
At this point, it would be best to strip and brighten to remove and use a stain that will not have a curring issue like the Defy Extreme. Defy is water-based (AC is oil) and will cure 100% though you still have to watch for over-application as that could reduce in wearing and peeling with a water-based stain.
FYI, we used AC on 100s of our customers decks every year without issues.
I used an oil based sealer and stain when applied it was hot and humid it took forever to dry
We had built a deck three years ago, stained it the second year. There is a tall birch tree over my deck. Our patio is black this year. We used deck cleaner, some came off, some didn’t….Now what to do? Any suggestions? Do i go with a darker stain? My color before was Honey Gold! Have a great day!
Strip it and brighten the wood, it should get the color back to the original wood.
Thompson’s waterseal immediatela
y tuned my redwood deck black. Why?
Could be many things. Post a picture.
Beware of Penofin. Check GOOGLE for others who have had disastrous results. I sanded my cedar deck to bare wood and used Penofin Marine grade top of the line stain. 3 months later dark grey. Sanded it down again same results. Sanedebdown again same results. After 3x I gave up.
My deck turned black.I applied a cleaner and have pressure washed it several times. Ther are still small stains here and there which only seem to come off when pressure washed so close the wood is in danger of being damaged. I have even tried brushing. There seems to be no end to it. I live in a warm humid environment. The old stain is gone now,but the marks are there. During pressure washing, it seems that I remove them. After drying, there are always some left. I am at my wits end.
Try a wood brightener.
I had a deck renewed last year. All verticals were in OK shape and were re-stained with a solid stain. All horizontals were replaced with new cedar and stained right away with Flood semi-transparent. A year later the horizontals were black in areas that were exposed to the elements, but still OK under chairs, etc. We tried scrubbing the horizontals with bleach and plastic brushes, which removed the black but also most of the stain (not all). Now it has been mostly unstained for about 3 months waiting for a break in the local rain. A contractor’s suggestion is to sand the horizontals and apply new stain. I’m cautious about using a stripper because I don’t want to remove the solid stain from the verticals, since it still looks great. What combination of sanding, stripping, and/or cleaning do you recommend before applying a new stain to the horizontals? Also, after this process, I’m thinking of using either TWP 100 or Armstrong Clark. Do you prefer one over the other in this case? I’m in central Texas, and the deck gets plenty of sun.
Deck Stain Strippers do not remove solid stains. We would strip and brighten the floors and recoat with the TWP.
have vertical pine vegas on exterior of southwestern home now have black streaks tried dilute clorox with some improvement. what should I do before re staining. should I use the deck cleaners mentioned?
Yes try a good deck cleaner and brightener like the RAD Kits for prep.