Apply Polyurethane to A Deck? 4.8/5 (116)

by Deck Stain Help

This post was updated on March 1, 2022

Applying Polyurethane Wood Deck

Welcome to DeckStainHelp.com, the internet’s number one reference for all things wood deck restoration related. As before, we do not recommend the use of polyurethane stains on outdoor decks. We always appreciate your comments and questions, so feel free to leave one below.


Should I Apply Polyurethane to a Deck?

Selecting a deck stain or sealer is a vital step when finishing your deck or when your deck is in need of being recoated. Wood decks are exposed to severe weather conditions and need to be protected with the correct type of wood sealant.

Peeling Deck Varnish

Peeling Deck Varnish

The best choice for finishing a wood deck is to use an exterior wood stain. A semi-transparent penetrating stain will provide adequate water and sun protection. This type of deck stain will enhance the natural beauty of the wood increasing its appearance.

When refinishing a deck, do not use a urethane, varnish, or polyurethane coating that films on top of the wood, creating a “shiny” finish. These types of finishes are mainly used for indoor applications and break down easily when exposed to the elements. Rain and harsh UV rays will cause polyurethane to fail quickly, which will subject the wood to weathering. The polyurethane will blister and peel on exterior wood. This will create a nightmare to fix where heavy sanding will be involved in the removal. If you want a clear or natural look to your deck, consider a deep penetrating (non-filming) clear deck sealer or better yet a semi-transparent deck stain in a natural tone.

Peeling Polyurethane Deck

Peeling Polyurethane Deck

When looking for the right deck stain you will find a large variety of colors. Finding a color like Natural, Cedar, or Redwood in a semi-transparent stain will not hide the wood grain as a solid stain or paint would. This can give your deck the natural look you desire while still giving the wood moisture and UV protection.

Do some research on your deck’s type of wood. Search for colors that will give you the final results you want. Do not apply polyurethane to a deck or it may jeopardize the deck’s beauty and longevity. The outdoor elements are too harsh for polyurethane making it a bad choice for exterior deck use. Keep your deck maintained with the proper choice of deck stain and it will be there for you to enjoy for many years ahead.

Please Ask Any Questions Below


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Dave Walker
Dave Walker
15 days ago

We built a redwood deck last year in higher elevation Colorado and it gets lots of sun. We were told not to use anything because we would have to redo every year. But the wood has started to splinter. What would be long a lasting finish? We are too old to do every year. Thank you!

Ron Cutler
Ron Cutler
4 months ago

Why do cruise ships use gloss varnish on all the rails..extreme exposure in that situation..
regards
RON CUTLER

Elmer
Elmer
7 months ago

The patio deck was painted with latex paint by the previous owner. We’ve sanded it off in preparation for applying primer & oil paint. The owner liked the sanded down version better than the paint options & said stain it & varnish it. So we stained it & was prepping to varnish it with Spar Varnish but Alas the internet is sending forboding anti-varnish vibes. ( It’s Tuesday night & we want this thing dry & not smelling like varnish by Saturday noon).

What would you do?

I’ve been advised to put linseed oil on it all instead, to avoid the chance of varnish still being tacky or smelly by Saturday. This would make the whole thing quite dark & dark was not meant to be dark

Should we give up & paint it with solid oil paint ontop of the stain?

This is in tropical rainforest. There is a lot of humidity. There is a roof over this deck. Outside of the roof, we are in the top 20 places in the world for highest ammount of rainfall

Alison
Alison
8 months ago

My deck was recently power washed and stained. I have an exterior spar urethane I wish to apply to the railing. Is this advisable. It is a clear gloss

Brynn
Brynn
8 months ago

Hi, I have recently stripped and sanded a huge deck that is 5 years old. It has direct sunlight about 8 hours/day. Live in OK- so we have all 4 seasons- often multiple times of the year! I love the color of my deck right now- the rustic blondes, mixed with the browns and weathered worn lived-on look. I am looking everywhere trying to figure out a way to just put a clear sealant to protect from UV and weather- but I don’t want to change the color, and I want to keep the Flat/Matte look of the wood. Any type of semi-transparent stain is going to change the color. (I’ve tried many attempts). I have researched water-based Polyurethane to keep the color the same, that’s as close as I can find. Any suggestions???

Debbie
Debbie
10 months ago

I painted my deck with glidden porch and floor paint. I want to seal it so the paint does not chip off. Can you please tell me a specific sealer I can use on it?

Hettie Rohwer
Hettie Rohwer
11 months ago

What sealant can I use on my 100 year old covered porch that has been stripped. I want something that will scrub off and not need a stripper. In the past used double deck natural, and scrubbed it with bleach each spring. It all came off and I recoated it each year. It always looked wonderful. Then 3yrs.ago my husband bought Bher deck natural stain. It wasn’t bad at first. By the 3rd year it was off in some places and really spotty looking. I’m in the process of stripping it using Bher deck stripper. WHAT A MESS. It’s very hard, the stripper works slow and is needing 2 or 3 applications and heavy scrubbing with a stiff brush and pressure washer. I have a very large porch that swings out in a circle at one end. So far it’s taken 7hrs to do a 5×8 area. What a nightmare!! Is there a type of oil I could use. Please help, thanks

Katie B
Katie B
11 months ago

Older deck; I have three zones of decking hell within a 10′ X 24′ porch. Only 33% exposed NOW that carport roof repaired. Was effectively 66% exposed prior. Guy used a brown poly/oil (found the can in shop) and it is shot in “exposed”, looks “ok” in “not exposed”. I own a pressure washer and am about ready to “hit” it. So, three levels of “mucked-up coming and going”. Am imagining I will need to drum sand entire, but trying to avoid. Recommendation? I see no proof my pictures are posting, but if you will use email provided, I could send pictures. The deck was NOT properly “spaced” between boards and multiple other “what was he thinking(s)”. Carport supports “sit” on top of deck,so total “redo” with composite or other brings a world of structural shenanigans. Only option is “prep and re-seal”.

Jim
Jim
11 months ago

My deck was previously painted. I did a light sanding, then power washed, allowed to dry thoroughly and then put my first coat of deck paint on. Same color. Same deck paint. But the deck has a a slight tackiness to it. Have I done something wrong? What should I do now?

Jim
Jim
11 months ago

Would putting an oil based second coat over the latex first coat work without having to wait? Or is there a clear coat I can use to seal the paint?

Jim
Jim
11 months ago

Thank you

L Miles
L Miles
11 months ago
Reply to  Jim

Why use latex on a deck?

Rick
Rick
11 months ago

I have a covered porch that has minimal exposure to the elements (just the steps and perimiter.) It is made of good quality wood decking material that has held up extremely well for 15 years. I restained it with a gel stain that has some glaze in it. It looks great and I wonder about adding a top coat to keep it looking that way. Something that will give general protection like an interior floor but is ok to use outside?

Jon
Jon
1 year ago

Here is my issue. I just built a brand new deck. I like so much better the interior stains that you rub off because they pull out the wood grain 100% better that the semi transparent deck stain/sealers out there that you just paint on. My question. If I use the interior stain outside… what can I use to seal it with???

Last edited 1 year ago by Jon
Matt
Matt
1 year ago

What can I put on top of my natural deck to make it look shiny like a wet look at all times it already has a 10-year clear sealer on it but I want it to to be shiny kind of like a dance floor

Gretchen & Kevin Revere
Gretchen & Kevin Revere
1 year ago

I currently have a painted stain (I think) on our porch that peels every summer. I need to get the current pair/stain off and do what you recommend. Should I just use a paint remover or should I rent a sander and remove it that way? By the way we have a very large porch.

Jeff
Jeff
1 year ago

If I can apply polyurethane to the wood on my boat and it be fine and exposed to lots of water and outdoor elements, why can’t I put polyurethane to my deck?

Mo Sida
Mo Sida
1 year ago

We have decking which has been painted light grey, have no idea what kind of paint. Can you suggest any paint that would look reasonable and survive for a while please?

Michelle Wilkinson
Michelle Wilkinson
1 year ago

Hello, we recently stained our newly built deck with a semi- transparent water based stain (Sherwin Williams Super Deck). After only a couple of days, I’m noticing visible scratches from my dogs feet. Is there some sort of top coat we can add that will lessen the wear and tear so quickly?

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David Belitsky
David Belitsky
1 year ago

I have a backyard deck, unfortunately, he previous owner re-finished the deck with Sikkens Polyeurathane. Some will say not a good choice because it will blister and peel. The real problem is that the finish is so slippery; that no one dares walk on it when it is wet, or much worse, when it is snow covered. (About six months of the year, here.) I think the only way to make this deck a walkable surface is to remove the Doug fir decking and replace it. Then stain the new wood.
Polyeurathane should be illegal for outside decks!

michael
michael
1 year ago
Reply to  David Belitsky

hate to waste the Doug Fir – what about sanding deck, then apply oil based semi-transparent?

David B
David B
1 year ago

What is the solution? I see discussion of aliphatic polyeurathane but then a comment that it is not intended for exterior use? Of course we could get a floor sander and strip the deck but it’s a big deck, probably a two-day process. Then there’s the issue of the sander planing off the natural texture of the fir planks. One comment recommends applying semi-transparent stain, after sanding, which would be fine, as I have lived with a stained deck. It’s just a huge undertaking. I still think that building codes should prohibit poly-finish on exterior decks.

Joseph
Joseph
1 year ago

Have you heard of aliphatic polyurethane? Those are impervious to UV radiation, as UV will pass right through it. It won’t prevent what’s underneath from reacting with UV, but as a wear/chemical/water resistant sealant/top coat, it does admirably.

What should I do from this point on
What should I do from this point on
1 year ago

What should I do from this point on

Kent Thomas
Kent Thomas
1 year ago

Hi,
I have a deck made of IPE & PURPLE HART and would love to keep the colors from fading any ideas for a clear finish. full sun!
Thanks

Hal Cox
Hal Cox
1 year ago

I have just replaced the wood on a 20 year old deck that was deteriorating, I did not replace the wood under 2 covered areas. All the wood, both old and new is treated pine. I plan to Stain and seal the deck next spring after the new wood has seasoned some. The old wood has been sealed with Thompson’s Water Seal probably twice over the last 20 years but it was around 10 years ago the last time it was done. The old wood doesn’t get much sun or water and it is just a little gray. Question; what do I need to do to the old wood before staining, I want it to be a dark stain. And will it be possible to get the old wood and the new wood to stain close to the sale color?

Susan
Susan
1 year ago

My deck was built with the poorest quality wood available (I am livid). The wood is already splintering, splitting and in general a total mess. I have gone ahead and treated it hoping to save….something. What would be the best treatment to apply? The quality is so poor that the railing tops are already “flaking” and splintering. If I could clear coat it I would to avoid getting splinters just by resting my hand on the railing. Deck was built in June 2020.

Victoria
Victoria
1 year ago

I built a bathroom vanity top out of oak. Will a deck stain (that contains sealer) be sufficient to repel water and stains or do I need some kind of topcoat?

Troy Colligan
Troy Colligan
1 year ago

I have an enclosed 3 season porch with mahogany wood that needs to be sanded down and sealed. Do you recommend a marine varnish or lacquer to bring out the mahogany color and seal it right?

Troy Colligan
Troy Colligan
1 year ago
Reply to  Troy Colligan

Thank you. I have two flooring companies recommending varnish and lacquer so I find this quite interesting. I read this site often and find your information valuable. We live in the Northeast and the enclosed porch can be subject to the weather. The mahogany is not being used as a deck. Are you saying you would only finish it with stain to seal? What about Sikkens? or Cabot although I heard this one is no good.

Troy Colligan
Troy Colligan
1 year ago

Thank you. Can you recommend a quality hardwood stain?

Pearl Ruby Torres
Pearl Ruby Torres
1 year ago

We have an upper deck with new tongue and groove planking. We want to use a stain or sealer that will keep the rain from seeping through the seams?

Lydia Mary
Lydia Mary
1 year ago

Have a tigerwood deck, does a water sealer work or even necessary?

Mark H.
Mark H.
1 year ago

Hello! We have just sanded down our covered porch floor that’s in great condition (early 1900s T&G Fir–it was protected by many many coats of paint and then carpet); we’d like to stain and seal this, so the beautiful grain can be seen through, but would like to stain it a little darker in color too (so not looking for a clear finish). What products would you recommend? We’re unsure of Waterlox, Thompsons sealer, and/or a spar varnish…Any help would be appreciated!

Richard Clelland
Richard Clelland
1 year ago

Our 10 year old composite “wood” deck is showing wear. What can we use to refresh the redwood color and preserve the finish?

Tom vermullen
Tom vermullen
1 year ago

3 years ago I applied a solid color stain. Big mistake. I sanded as much off as i could, some still remains. Can i apply a stain or sealer that will hide or at least disguise the remaining stain? The deck is 30 years old but still in good condition

Terry Dickens
Terry Dickens
2 years ago

I have a customer who has a screened-in deck floor that is sealed with what looks like Marine Spar Varnish. It is a glossy sheen. Their are 3-4 areas that are lifting due to the limited sun exposure, and not keeping it maintained every year. Overall, its in great shape, but the varnish and stain will have to be removed down to the wood, and then re-stained again in order for the floor to look consistent. They want the gloss varnish look again. I’ve never recommended any kind of varnish on a deck floor. What are your thoughts since it is a screened porch?
Thank you for the help!

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Zack
Zack
1 year ago

Why doesn’t the spar urethane on boats peel?

Brenda
Brenda
2 years ago

Hi. I live in London, Ontario, Canada which has humid, hot summers and wet-cold to dry-cold winters. I have an older deck, open but with a roof, that I’m going to power wash, strip, sand and let dry before I do the 2-coat stain, sand between & seal process. I want to protect it using an exterior polyurethane. My research supports your opinion of not using regular exterior polyurethane as it doesn’t last. However, I’ve found several articles that support using 3-coats of spar polyurethane which is for exterior wood as it has a high UV protection rating and will last in the elements.
Would you please comment on the use of spar polyurethane.
Thank you.
Brenda

Kristi VanDerVeen
Kristi VanDerVeen
2 years ago

I would like to restain my deck but am not sure what to use to get the results I want. It is not covered and is on the NorthWest side of our house, in Kansas, so it gets the extreme hot sun in the summer and snow in the winter. I have used Cabot’s Australian Timber Oil the past several years, and I love it when I first finish it. But it has been approximately 6 months since I finished it last and now looks as if I hadn’t put anything on it. I am wondering what I can use that will last longer 6 months before needing a re-application. I looked into Spar Varnish, but also see in your older comments about the use of varnishes (or does this not apply to Spar Varnish- different components than regular varnish?).

Brian van Vliet
Brian van Vliet
2 years ago

I know of someone that used a lacquer that is normally used for wooden boats as the final coating on his backyard deck. I live in Alberta where we get pretty harsh winters. What are your thoughts about applying something like this?

Brian Morgan
Brian Morgan
2 years ago

I have a customer that wants a clear coat on a Ipe deck and would like to know the best product for that

Wood polyurethane work on pressure-treated wood th
Wood polyurethane work on pressure-treated wood th
2 years ago

Wood polyurethane work on pressure-treated wood that’s been dried at least two years. These decks are totally covered from the sun. Your help would be appreciated

Joan
Joan
2 years ago

I have a ~ 10′ x 10′ “interior” redwood deck in an atrium that is covered by correlated vinyl roofing material (such as for a greenhouse). It is adjacent to my kitchen. It is edged by 2 interior walls and two exterior walls. (Put in by previous owner w/o any means of ventilation other than when the slider to the outside or the other slider to the kitchen are open.) I made the severe mistake of putting a water-based polyurethane coat over oil-based polyurethane, wanting to create a more glossy surface and look. Quite frankly, the oil-based PU seemed to hold up well without any peeling. etc. BUT, the water-based PU bubbled/lifted up in several places. Now I’m working hard to strip all this away. My plan was to then reapply a PU. But since you recommend against that for outdoor decking, and since this does get wet from condensation now that I have great sealing sliding glass door in one of its surrounding walls, maybe I shouldn’t? I’d appreciate your input. Thanks.

Elwood Waites
Elwood Waites
2 years ago

I have 3 sets of treated wood steps in middle Georgia that I have pressure with Clorox and jomax. I need a good clear sealer that will last for these. What do you recommend?
Also I have a wrap around covered porch that I did the same cleaning to but don’t plan to seal since covered. Your thoughts?

Elwood Waites
Elwood Waites
2 years ago

Ask a Question or Post a Review…On second thought the cabin is stain in the brown color. So maybe could stain with a lighter brown. What would you recommend? Would the stain need to be sealed?
Anything on covered porch?

Joshua Darrell Shelton
Joshua Darrell Shelton
2 years ago

I have white oak in my kitchen, with a Minwax provincial stain, a satin polyurethane. I’m going to stain my deck. What would be the best possible match for my deck.?? Any suggestions would greatly be appreciated.

Brian
Brian
2 years ago

So are you saying there isnt a poly product on the market that can be used successfully in an exterior application?

Brian
Brian
2 years ago

I know you’re only decks but can you recommend something for a wood floor on a covered porch that will protect from water, uv and prevent (as best as possible marring or scratching the wood surface from furniture?

Karen
Karen
2 years ago

Hey there. So my contractor just built a beautiful deck, but then one of his crew applied a coat of interior poly on top of it. I told him he needs to remove it so we can put something more appropriate on (a transparent stain likely), but he’s pushing back, saying we can apply something on top of it. Like an outdoor clear sealer. I’m arguing that it won’t work, as the outdoor sealer won’t stick to the poly, and the poly will just crack and blister pretty quickly.

Can you please chime in so I have some back up? What would you do? Chemically remove the poly, and then let it sit until spring, and then stain? (It was build a few weeks ago). I live in Vermont, so it will get some serious weather this winter.

Thanks!

Casey
Casey
2 years ago

I have a mahogany deck that has had one coat of Sherwin Williams deck sealer. Realizing I want it to look more like the wood has “popped” instead of the dull grey. Any suggestions on refinishing and getting more of a wet look?

Mario Amodeo
Mario Amodeo
2 years ago

I just used a deck sealing stain, Super Deck transparent stain (cedar) on the pressure treated deck I just built in Southern California that allows the grains to show thru and seems to be what is the recommended procedure, but I’m worried about splinters on my 3 year old’s hands. If varnishes like poly and marine varnish are no good for outdoor decks, how then to avoid the kids getting splinters? By sanding? I don’t know about pressure treated wood on the west coast, but splinters from pressure treated wood back east can burn. Thanks in advance!

Ricardo Echeverria
Ricardo Echeverria
2 years ago

Hi, I am seeking for a good finish product for an exterior teak deck we are going to install in Guanacaste, Costa Rica. Our inital plan was to use a urethane varnish from Pinturas Sur (Speed Dry Satin Varnish is a single component, solvent base varnish, formulated from urethane resins.
Thanks to its features, it protects surfaces exposed to environmental conditions such as sun, rain and
humidity. Quick drying, it provides a transparent satin finish, smooth and long lasting. It protects and
highlights the natural beauty of wood.)
Also, some other guys are recommending Carver Protect Deck, which is a water based penetrating finish).
What are your thought on this?

Haz
Haz
2 years ago

Your review of the Flood Pro stain for decks has Urethane which you state stops cracking. YET HERE you say dont use Urethane.
Wow

Rosanna Wildermuth
Rosanna Wildermuth
2 years ago

I just stained my front porch with cabot premium wood care, The Ultimate finish (Moonlight Mahogany) I absolutely love the way it Looks! After reading all the reviews and your recommendations I’m very nervous that it won’t stand the test of Time! I plain on using a water based stain on my back cedar deck. My question is can i go over the Cabot stain on my porch with the water based stain to hopefully give it some extra stay Power?

jack
jack
2 years ago

I’m actually building a backyard climbing wall. We want all the water/UV/weather protection we can get out of these deck stains but also want there to be a slick texture or film over the wood so that it is not just a wood texture. This is what brought me to this article because we like the texture that 3-5 coats of polyurethane gives you.

We live in Southern California about 30min from the coast. The walls will are under shade at least 50% of the day, and will also have a UV screen in front of it when not being used.

Any ideas on how we can accomplish?

Ann Kleva
Ann Kleva
3 years ago

We built a porch with ezy breeze windows room over new deck, treated pine wood flooring. We want to use an oil stain on the floor and protect it with a satin coating. What is the protective finish we should use, or oil based stain enough?
Thank you.

Bobbi Ball
Bobbi Ball
3 years ago

I live in cold and snow country. My deck is 5 years old and every year, I have to re-stain it. I have used everything.
NOW, I want a solid paint, something that will last. I am tired of the every year upkeep. What can you recommend
that will last. Seeing the wood through the stain is not important anymore. My deck looks horrible right now, and I want a clean and fresh look.
Thank you,
Bobbi

Bobbi Ball
Bobbi Ball
3 years ago
Reply to  Bobbi Ball

I want a paint, I have already used a solid stain, the wood is always sanded off. Nothing works

krakatoakt
krakatoakt(@krakatoakt)
1 year ago

What would you recommend if the item is vertical (fence)? I hate painting, so want something that will last fairly long term. If the wood was previously stained, can I paint it? I have some not previously stained and some that is.

Thanks

Timothy
Timothy
3 years ago

Hi I’m looking to put something on my interior honey house deck, it is raw spruce plywood. It never sees sun or rain, but is walked on and gets wax/honey on it. What would you recommend?

Thanks

Carol Pollard
Carol Pollard
3 years ago

My contractor put marine varnish on my new redwood deck and now dark discoloring seems to be happening. He said it needs another coat (after some sanding) to provide protection but I’m fearing that he made a big mistake and I might need to sand it off and start over. Help! Thanks.

Carol Pollard
Carol Pollard
3 years ago

Thanks for the help. I’m learning a lot!

Danijel
Danijel
3 years ago

Would a polyurethane coat be suitable on decking that is partially outside? The laundry room is built on top of the decking and is enclosed on all sides.

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