This post was updated on March 1, 2022
Why Did my Deck Stain Turn Black?
We appreciate it 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 stains 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.
Deck Stain Help & Questions
Stain Reviews & Comparisons
Products & Brands
As an article and comment contributor to the site, Scott has been around the pressure washing industry since attending college. In 1993 he started his first company called Oakland Pressure Wash specializing in exterior pressure washing and deck staining. That company evolved into OPW L.L.C. shortly thereafter concentrating more on exterior wood and deck restoration. Scott and his Deck Cleaning Michigan company have restored over 10,000 decks in the Metro Detroit area since the early years. He has become an authority in the deck restoration industry and has contributed to numerous wood restoration forums and informative sites.
All the products he suggests through this site are sold through online sites and in retail stores, allowing the consumer to choose their own means of purchase. Scott’s eCommerce sites do sell many top brands he endorses and if you appreciate any of the help he has offered then feel free to purchase from one of them.
HI, Is it possible that splatter from a bluestone stoop is causing staining on a douglas fir porch? The deck was treated with penofin. The splatter marks come after heavy rain. The porch is covered.
Sorry but no idea but definitely coming from something else.
Hi I just stained my new deck waited one year before doing so, I used the cleaner and brightener first then one coat of stain, then it did rain hours later which was not suppose to, but a small part of my deck is a little darker than the rest, should I put another coat on the part that is lighter so it will match? It really did turn out good but now I’m not happy with the look since one part is little darker.
More is not better and it may not take another coat so leave as is.
We just had a fir tongue in groove porch floor installed. It was stained & sealed with Ready Seal and looked good for 2 weeks. It rained on Thursday night and the deck is black (see attached picture). Our poor builder is ready to rip the floor off and start over. Thank you for any help you can provide.
That looks like rust. Someone got metal in the wood. Could have been from cutting with a metal blade or steel wool, etc. Strip and brighten for prep with Restore A Deck Kits.
Hello, Scott. Thank you for giving us this forum. We are in the process of re-staining our deck. We just finished sanding it using an orbital sander and detail sander. Then we power-washed it and dried it with clean rags, using a bit of pressure while wiping to remove any remaining dirt. Would you recommend that we proceed to stain or should we wash the deck with a deck cleaner then follow with a wood brightener? This is our first time doing this so we want to do get it right. I’ve attached a couple of pictures for you. Thanks in advance for your input! We really appreciate it!!!
The wood looks very smooth. What grit of paper did you sand with? Does water bead on the surface or soak in right away?
We used 80 grit. I just poured a drop of water and it beaded on the surface.
The stain will not take then. You may have to let it sit for 1-2 months and then clean and brighten for the prep.
Thanks, Scott. I tried staining in an inconspicuous area and it looks like it took the stain provided that I applied with a brush (back and forth motion) then wiped off the excess with a clean cloth. Do you think I should still wait a couple of months? Can I try staining it now and if it doesn’t last, clean and brighten in a few months then re-apply the stain? Thanks again for your input. This forum is really helpful.
The easiest thing to do is just wait until Fall, prep, then stain with one coat. We would not do it now.
Thanks, Scott! I will do that. Have a good rest of your week.
Thanks!
Hi, I found your site too late it seems. I heavily pressure washed my deck to strip off the old stain. In the process I damaged the surface slightly in few places. I belt sanding most of the rough spots. It seems to me my deck is very clean now and most boards look bright, but I have a few darker boards standing out. These have move cracks and have a slight bulge. Can you tell from my photos whats up with these dark boards ? I plan to put Flood solid stain (light color). Since I heavily pressure washed my deck, do I still need to use a cleaning solution and/or a brightener ? Thank you so much and thanks for your informative site.
If using a solid stain you do not have to worry about the boards being darker or lighter in spots.
I see you recommend a brightener. Do i need a brightener in my case of ‘over’ pressure washing ?
No need when using a solid stain in this case.
Thank You!
I used Penofin Step#2 and pressure washed our Tigerwood deck and oiled with Penofin Hardware Oil Natural. After seeing my deck turn black I am thinking I need to completely re-clean and start over, but obviously not using Penofin products. I will state that not all of my wood had original color prior to oiling so maybe I needed to use more cleaner? However, even on the wood that was very clean and dry turned dark. Can you please provide me steps I need to take and best product to use? I wish I would have found this site prior to starting. Thank you! Not sure my photos attached.
You need to strip and brighten for prep. Once removed, try Restore A Deck Stain in Light Walnut color. Use the Restore A Deck Stripper/Brightener kits for the prep:
https://www.deckstainhelp.com/restore-a-deck-injectable-deck-stain-stripper-review/
Why is my decking looking this is. I have now used red label to strip the Ron seal deck stain off. It was put down last year and just looks dirty all the time.
Post some pictures.
We have Penofin red label on our deck for 3 years. It has darkened the most where exposed to the sun. We don’t want another coating of the Penofin. What can we use instead?
Thank you!
PS We don’t want to sand the deck.
Strip and brighten for prep with Restore a Deck Kits and then stain with Restore A Deck Stain or TWP stains.
Help! I have this big mark on the deck next to the wheel… The rest is grease marks from a bbq, not sure if this is the same or something more suspect?
It will not fully come out, too deep in the wood.
Do you think that all of it is grease stain?
Mostly grease, possibly some burn.
Can the moisture causing the blacking of the deck be underneath the deck? Lack of air flow under it?
Doubt it but if really bad and it is rotting from the bottom up, then yes you could have an internal darkening from the rotting damage. Rarely have we seen this though.
I have installed red cedar clap boards with the rough side exposed some 15 years ago on my house. I applied Penofin Ultimate Premium Western Red Cedar oil stain shortly after installation and reapplied the stain over time. The cedar clap boards did turn black. I prefer not to go through the process of the stripping process before reapplying more stain. Can I use TWP (oil) 1500 Redwood to the already Penofin stained clapboards to lighten the color? I am also concerned that the two products are not compatible. Thank you
No, you have no choice to remove the Penofin by stripping before using any other semi-transparent stain. Use the RAD stripper kits: https://www.deckstainhelp.com/restore-a-deck-injectable-deck-stain-stripper-review/
Hi i was reading up Penofin stain. So you guys dont recommend them anymore? I lice in Canada and TWP, AC and Defy do not have a dealer here. We do however have Penofin. If you dont recommend Penofin, what orher products can we use aside from above mentioned product. I understand we will most likely need to re-do the sealing more often. Thanks.
We stopped using Penofin the early 90s due to their issues with the stain darkening and turning black. Plus it smells really bad. Ordering the TWP or AC from the states is your best option if you cannot find them locally.
older redwood deck use oil or water base stain
Does not matter as long as you prep correctly and use a quality stain: https://www.deckstainhelp.com/the-5-best-deck-stain-reviews-and-ratings/
I had my pressure treated wood deck repaired, cleaned, and stained a few months ago. Now many areas are black. Did the company I hired do something wrong? Anything we can do?
Thanks!
No, it is not their fault. Looks like leaf stains, dirt, mildew, etc.
Thanks! Normal for stains and mildew so soon after staining? How can we remove without harming the deck?
Is it normal for stains, mildew, etc so soon after staining? What is best option for cleaning without damaging wood or stain? Thanks!
You cannot prevent stains from leaves decomposing unless you remove the leaves right away. Mildew can happen no matter what if in a wet environment. You cannot just remove the dirt, stains, etc, and not harm the deck stain finish at the same time.
I have black dots over half of a brand new cedar floating dock for I built for our pond … it’s been in my garage since Mother’s Day I just pushed it out Friday July 17th, it rained on it Sunday, Monday morning black specks all over half the deck… it has not been stained or treated with anything….is it mildew?? I tried power washing it out with no luck it sanded out a little but not easily. What can I use to remove the specks??
Thanks Michael M
It is mildew or rust. Bleach removes mildew. A wood brightener removes rust.
I thought I was doing everything right restaining a cedar sided house. It’s originally stained with Penofin Transparent Cedar red label and I am applying the same thing.
The house was last stained probably 5 years ago, working on the south facing side, the cedar has lots of black or dark patches at the bottom of the vertical cedar siding. The upper 2/3rds is in relatively nice shape still.
My prep-
Using Penofin Cleaner – dissolving in water and applying with a pump sprayer, letting it activate for about 20 minutes and then scrubbing the surfaces, doing a second application on the lower areas that have the blackest staining. Hosing off with garden hose
Using Penofin Brightener – dissolving in water and applying with a pump sprayer, letting it activate for about 20 minutes and then doing a second application on the lower areas that have the blackest staining. I can visually see the dark areas lightening during application. Hosing very thoroughly with power sprayer, making sure not to damage the wood, but enough that some mushy wood fibers are showing up and being washed off during the spraying.
Letting dry 24 hours.
The surfaces look great, much lighter, black staining gone, cedar looks almost brand new.
Reapplying 2 coats of Penofin red label. However, this is where I am having the problem, as soon as I apply the first coat, the darkness at the bottom if the cedar, very ugly seems to reappear. The nice bright even surface is dark again at the bottom as if I never did any prep.
I stopped, only covered a small section with one coat, I don’t want to go any further until I know what steps to take, or is it possible the wood is so old it’s just beyond coming back to like new?
Picture below -shows before, after cleaning, after restaining
Looks internals water stains near the bottom causing the darkening. Nothing you can do about this as far as prep or a different stain brand.
Hi thankjs for the quick reply. I’m confused, what are “internal water stains”?
THanks
Water damage in wood turns black in color and cannot come out. Most likely moisture wicked up from the froof and started to degrade the wood cell structure. It is a permanent discoloration.
Hi,
Sept. 2019, I contacted Rustoleum to report the Deck Restore product, with a limited lifetime warranty that I purchased through Lowe’s, was all peeling off. They first tried to offer an inferior stain to repair the surface. I finally got to David Summers the product manager for Rustoleum. His final offer, after working this issue for months with Rustoleum was to refund the purchase of the product, purchased 8 years ago, if I have the receipts, or they provide a product replacement with no future warranty. I cannot get all the old product off with a pressure washer, and it was too late to apply, as the temperatures are too cold for the product to set. My only option is to replace the deck floor. I asked for Rustoleum to cover material only, and he indicated a limited warranty only covers the Restore Product costs. I am still working this with Rustoleum and wish there was a current class action suit. All I wanted was for them to provide their current similar product for me to cover the deck and extend the warranty for lifetime. They refused.
That does not surprise us. These “extended” warranties are BS and the companies do not back them up.
Hi there. Had brand new deck installed 7 months ago ( treated wood). Read multiple articles on your site and prepared wood with Restore-A- Deck products and then ordered recommended good quality Armstrong Clark wood stain. 3-4 months later noted black residue on the surface of the deck, currently so bad it almost leaves marks on the soles of my feet when walking barefoot. Not even full year and deck has completely different color even though good products were used and followed all instructions to prep and stain. Located in NJ.
I was planning on cleaning the deck in the summer and restaining with TWP instead? Not sure what happened but it looks bad.
If the mildew is on top of the AC stain then it is impossible to prevent. Stains can prevent or stop growth in the stain but no stain can stop or prevent mildew growth on top of the stain. Mildew can grow on any surface. It also could be an issue with pollen. Pollen is a known mildew promoter and that could have fed the growth on top of the AC. It wouldn’t hurt though to switch brands and see if you have fewer issues since you will need to redo anyhow. Try the TWP 1500 Series or Restore-A-Deck Stains.
Hi there. Thanks for all the great advice on this thread. I’ve just had my deck sanded and re-oiled. It was last oiled about a year ago and was definitely ready. They sanded and applied three coats in one day, and now checking it the next day there are lots of black marks in the wood. Could you advise on what this is from and how to fix it? The wood is Ipe. Thank you!
It looks like burn marks in the wood from the sanding. Not any easy fix. You would have to strip and then resand all property. Brighten the wood after.
Brand new cedar deck has all these black leopard print like splodges all over it. It appeared after the first rain. No metal sanding as been done anywhere near it. No railings even installed yet! Almost looks burnt in places. This is a professional install.
Any suggestions?!
Definitely, something in the rainwater caused this but not sure what. Hopefully, a good cleaning and brightener will fix this/ See here about new wood: https://www.deckstainhelp.com/staining-a-new-deck/
Hi – this is my merbau deck that was put down 10 months ago. It has gone black apart from area that were covered with furniture? Any advice on best way to deal with this? Thank you Jackie. ps please ignore one picture there it’s my fence- sorry can’t work our how to delete it now!
Has it been stained before? If so, strip and brighten for the prep: https://www.deckstainhelp.com/restore-a-deck-injectable-deck-stain-stripper-review/
If not, clean and brighten for the prep: https://www.deckstainhelp.com/restore-a-deck-cleaner-system-review/
Just wondering what these black marks are
Probably rust coming from your metal gate. Turns black in wood.
I don’t have a metal gate
The deck is only one week old
Yes, you have a black metal or painted hinge in your photo.
How do I remove it
If it is rust, a wood brightener will help to remove it. Your bigger issue is it will continue to rust from the hinge unless you fix that.
I just had my spotted gum Deck done last week
After I hosed it all down black spots appeared not sure If this is normal
Anykne got some advice with this matter?
Post a picture.
Hello,
Our deck went without staining or 4 +/- years. I bought Sherwin-Williams Revive and cleaned, scrubbed and washed/power-washed the deck. After drying for 48+ hours I applied Sherwin-Williams Superdeck oil based stain. We have no nearby trees/shrubs. The deck showed no black spots prior to staining. It was just dry. Can I fix this by applying another brand of stain?
No, you will need to strip it off and then brighten the wood. The black was there internally in the wood. The SD just enhanced it.
Thank you.
I have what is probably a dumb question here. I stained our porch last Summer and after a year of taking a beating from the weather and foot traffic it’s just dirty and need some minor touch up in a few areas. Should I just hit it with a deck cleaner to make the appearance better? Should I use a cleaner and brighter to help the appearance? Again, just a few touch up areas I would like to hit with a brush. Thanks for your advice (again).
Deck cleaners and brighteners are for prepping for recoating, not general cleaning. If you use them, you would need to most likely recoat all the floors, etc. but that would vary based on the type of stain you have.
I have an old deck, previously stained. Cleaned it with a deck cleaner (scrubbed with a brush, rinsed), then let it dry for 48 hours. Moisture meter showed less than 15%. Applied a coat of Cabot Semi-Solid stain. Unfortunately, an unpredicted rain occurred overnight, about 12 hours after application. Let it dry for about 10 days. During that time, have had rain every 2-3 days. The deck now is dry to the touch, but some areas have dark, shiny streaks (see photos). These boards also collect water more than other areas, so I suspect that the stain may have been over-applied. Is there a way I can clean up the dark areas without having to re-do the whole deck?
Nope, you would have to redo all.
What do I have to do to make sure the black doesn’t come back? Will a deck cleaner be enough or do I need to strip or sand it?
This cannot be stripped, power sanding to fix this. Once prepped correctly, a good stain will not do this.
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.