Can I Use Wood Filler for Decks? 4.4/5 (60)

This post was updated on March 7, 2022

Decks can crack and split as the wood ages, leaving large voids on the surface, and it can be tempting to fill these voids with an outdoor wood filler. But as the Internet’s top authority on wood deck restoration, we do not recommend that you use wood filler or caulk for your decking projects. However, we are always interested in hearing about your experiences with deck restoration as well: If you’ve tried using wood crack filler on your deck or are thinking about doing so, feel free to leave us a comment or question below.

What Is the Best Exterior Wood Filler for Decks?

We can’t recommend any caulk and wood filler products to fill cracks in a deck: Using wood filler for decks will not give you a good result.

Should I Fill Cracks in Deck Boards?

No, it’s best to leave cracks be. They won’t be detrimental to the deck, and any wood filler product will eventually fail anyway.

What’s Wrong With Using Exterior Wood Putty on a Deck?

One of the biggest problems with using wood filler or caulk on a deck or wood surface is the instability of the filler. Wood putty tends to crack or break out of the voids you put it in when you use it on wooden decking. This is especially true in an area that gets wintry weather: The natural freezing and thawing processes will quickly cause wood filler and caulk to fail. Also, outdoor wood filler doesn’t look natural on a deck.

Can You Stain Wood Filler?

In general, it’s challenging to put stain over wood filler, and we don’t recommend doing this. Many homeowners have asked about using wood filler or caulk with stain, but it usually looks unsightly because you end up with an uneven color pattern. The wood filler does not stain to match the deck finish. This can be frustrating for someone staining a deck: No matter how hard you try, the caulk or putty will not look like the rest of the stained surface. It’s going to stick out like a sore thumb.

If you want to try staining wood filler anyway, make sure to sand down your exterior wood putty so it’s smooth, clean off the dust completely, and apply the stain in thin layers for the best results.

What Stain Covers Wood Filler?

If you are going to stain over wood filler, make sure to use a solid stain. A semi-transparent stain will not hide it; no stain will do a perfect job of covering wood filler, but solid stain will work best.

What Can I Do About Deck Cracks?

The best way to deal with cracks and voids is to sand around the area to lessen the size of the gap. In extreme cases, replacing the boards or turning them over may be the best option. But in many cases, cracks aren’t detrimental to the deck, so you don’t have to do anything. Some small cracks and splits will not hurt the deck’s performance.

What to Use to Fill Holes in a Wood Deck

For severe damage, like a rotted knot, you can try Perma Fill by Gulf Synthetics: That’s probably your best bet. But rather than use wood filler to repair rotted wood, in most cases, it would be better to replace the wood.

Can I Use Wood Filler on Pressure-Treated Wood?

Pressure-treated wood is full of preservatives that prevent severe cracks and damage, so you’re not likely to have cracking that’s bad enough to need filling. But we don’t recommend using wood crack filler on any type of wooden deck, including one made with pressure-treated wood.

Have a Question? Ask Below!

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Kris
Kris
29 days ago

We had a new deck installed in November 2021 (we live in Georgia). The wood is pressure treated and it now has long cracks down the posts some of them look deep. There are some cracks on the deck boards as well. What should we do?

Kris
Kris
29 days ago

Even when it looks like this?

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Alice
Alice
1 month ago

how can I restore this deck?

Linda
Linda
1 month ago

HI there, May I ask what you mean that the wood filler will fail? Does fail mean cause rot of the boards? Or does it mean the filler will get dry and come out? Is the concern that using wood filler to repair cracks will look “ugly” under transparent stain or that using wood filler would actually damage either the boards (rot?) or make the paint job look bad or peel? Thank you!

Linda
Linda
1 month ago

Thank you so very much. If there was 1 coat of primer and 2 coats of paint on the wood, would you see the cracked wood filler? A company proposed filling the cracks with wood filler and then priming plus 2 coats of solid color paint on the deck (we also have three new boards that are clearly a different color). I am wondering why they would say that? Unless it makes the boards looks the most smooth and we would never see the cracked filler under all of the layers of paint? Is there ANY advantage to using a filler?

Linda z
Linda z
1 month ago

Oh my goodness! Thank you! You mean skip the primer part??? Or do you mean do not use paint, just use stain??

Patty
Patty
2 months ago

Any way to fill or hide those pressure-treated incisions? I plan on using a solid color stain. I just hate those marks!

Jeremy
Jeremy
7 months ago

If I will be applying a solid stain (RAD) which type of product for filling cracks/voids is best (mainly for longevity)
Noticed a few answers here saying it’d be ok if using a Solid stain. Epoxy. Filler. Exterior caulk.
Would you apply prior to strip or after?
I have cracks as well as splintering on our 15 yr old PT pine deck.

Susan Daniels
Susan Daniels
8 months ago

We had a new deck constructed this summer. The contractor placed caulking in the joints of the rail top. Now I read that it should not be done! How do I get that off? sigh……

Karl Adamczyk
Karl Adamczyk
10 months ago

Found this website too late. Just used some wood filler on big cracks, stained deck with semi transparent product. Colour difference between filler and deck boards is atrocious. In two years, when I re stain, will switching to a solid stain mask it better? I could also just reverse the boards too I guess.

Karl Adamczyk
Karl Adamczyk
10 months ago

Thank you for your feedback!

Kelli
Kelli
10 months ago

What can I use on the old boards before the solid stain is applied to fill in the weathered cracks? The replaced boards are obviously new and solid and I want them to blend better than they will as is; I’ve already purchased the solid stain it was mixed at Sherwin Williams.

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Kelli
Kelli
10 months ago

So, if not a filler, which was more a descriptive word I chose than product, is there anything that can be applied to bridge the visual gap between the 2?

Last edited 10 months ago by Kelli
Connie Crogal
Connie Crogal
11 months ago

What about a epoxy filler?

Harjeet
Harjeet
1 year ago

My deck posts are showing such cracks as in the pic. My contractor recommended to apply this exterior coating before painting/staining. Will this help for cracks to stabilize and not propogate faster and is it generally recommended to apply on the floor of deck before paint/stain?

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Harjeet
Harjeet
1 year ago

Thank you v much.

I have one more followup: on this solid stained deck (6+ years old), I dont want to go through the hassle of sanding the entire deck to remove old stain. If the stain can be removed with a stain remover, I will go for a semi transparent stain, otherwise I will go for a solid stain.

Are the below recommended steps to follow before I pressure wash and start staining

  1. Remove coating with stain and finish stripper – is this effective for solid stain as you see in the pic or I need to sand everything, making this step futile?
  2. Clean the wood with a wood cleaner – wood doesnt have mold/mildew, so is this step recommended to make the wood cleaner?

Please advise if above are recommended or should I skip these two steps and move to pressure wash and staining.

Harjeet
Harjeet
1 year ago

Thank you. I will go ahead and do another solid stain then.

This means that using the stripper has no value, correct?

Is wood cleaner recommended generally (even if there is no mold/mildew), before applying solid stain?

Harjeet
Harjeet
1 year ago

And no wood cleaner as well? Thanks much!!

Ed
Ed
1 year ago

I have a main Cedar post on my deck that’s in concrete. It’s older and one side is chewed up due to a gate that was on it & pulled out over time. Can I add a thin cedar board over it? I notice some that are a 1/2 inch thick or less for indoor use.

Was thinking it might protect the holes from the weather?

Ed
Ed
1 year ago

Thank you so much for your quick response! I have a follow up question…
Will any cedar board work or I’d there indoor & outdoor cedar? Is there a recommended thickness to use?

Ed
Ed
1 year ago

Do you recommend a particular brand of stain for a transparent or semi transparent stain? The deck has pressure treated flooring & cedar rails. It suffers from extreme sun during the day & weather exposure. Temps in the area range from high 90s to just below zero in the winter. The frame & posts are older. The railing & floor are brand new green lumber.

KARL
KARL
1 year ago

Great Help article. I was just about to attempt to fill small cracks in my deck boards with a wood filler. Glad I read this article first. I am just going to lightly sand the deck and re-stain with my transparent stain.

Curtis
Curtis
1 year ago

I completely sanded my 2 year old deck that had no paint or stain. I used Sansin wood stain and it turned out great.
It will be 2 years this summer since I stained, and there is like no peeling at all.
The only spots it has is where the boards end against a 2×10 on a ramp for wheelchair.
Is there anything I could put in the board end to prevent this from getting worse. Like an outdoor caulking etc ???? Thanks

Col Davidson
Col Davidson
1 year ago

Dear Sirs
I have a moderately large treated pine deck , originally painted with a dark brown Wattyl Decking Paint (Weatherguard – I think). Probably painted about 5 years back. For some time now it is showing major cracking – some cracks quite long but none wider than 1 to 1 1/2 millimetres. Further painting does not cover the cracks which apparently need some type of a filler. External position with temperatures ranging from minus 7degrees C to about 34 degrees C. I would appreciate your advice as to the how and what with to fill the cracks.
Col Davidson
 

Patrick
Patrick
1 year ago

I have some deep screw holes and joints that separated on my deck in Maryland. Anything recommended to fill and take a transparent or semi transparent stain?

Patrick
Patrick
1 year ago

Thank you.

I did read the article, but was hoping for something…….

I bought all weather silicone that takes on paint, was hoping that would work. Guess I’ll take it back and live with the issues.

Elizabeth
Elizabeth
1 year ago

Hi, My 87 year old dad just finished putting in a new deck. He’s very meticulous and does good work. He sanded all sides of each pressure treated, heat cured board. Then he applied 1 layer of semi-transparent outdoor stain to all sides. He then applied a 2nd coat to the top of the board. 1 year later the boards are getting cracking that runs longitudinally. The cracks are about 1/4 in wide and some are up to 3 ft long. The knots are also splitting and cracking. He lives we in the Pacific Northwest with plenty of rain and snow.
So, is there anything he can use to fill these cracks so that they don’t worsen? Preferably the fix wouldn’t take back breaking work to accomplish. Thank you much!

denisha
denisha
1 year ago

Hi my pool deck has slight cracks what should i use?

Darren
Darren
1 year ago

Can I seal around base of my summer house/bar. With exterior silicone it’s on a slab base thanks

Darren
Darren
1 year ago

Should I fill screw holes in new summer house / bar with exterior wood filler before using clear stain

Darren
Darren
1 year ago

Thanks

Michelle
Michelle
1 year ago

We have just installed a new deck with pressure treated wood. Should I wait until next year to stain, to let the wood weather, or would it be better to stain it this season?

Michelle
Michelle
1 year ago

Very helpful info on this site. Thank you!

Stefano Angelo
Stefano Angelo
1 year ago

I am planning to use Defy Extreme Solid Stain on my deck. I have some cracks that are unsightly and wanted to ask about filling those. Since I am using a solid stain I will not have the color matching issues of transparent stains. Would filling work intros case?

Stefano Angelo
Stefano Angelo
1 year ago

Thanks. Any particular type that would be better for the job? Wood putty? Exterior painter’s caulk? etc.?

Stefano Angelo
Stefano Angelo
1 year ago

Thanks

Jonathon
Jonathon
2 years ago

Hello,
I have a deck project were there are some severe cracks on the main support posts. They are long and deep. Since fillers and caulk are not recommended, what can I do to prevent these cracks from getting any larger over time after I redo the deck…?? As of now, the deck will be re-stained with a dark brown colored stain. Also, I have read that you should not use colored stain on the floor of a deck but instead you should use a semi transparent. Is this correct…?? The homeowner wants the deck all the same. What is the best way to stain the floor so it lasts for several years….??

Jonathon
Jonathon
2 years ago

Unfortunately the cracking is on the main posts and not the floor boards. The deck has a lattice roof and would be virtually impossible to replace without excessive cost involved.
Thanks for the reply and info on the semi transparent

Timothy
Timothy
2 years ago

I have a deck board with removed splinters from a chisel. Would it be ideal to sand, then stain over those parts? Wood filler them? Or replace the boards? Climate is harsh winters.

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Joe
Joe
2 years ago

I’m prepping a newer deck for eventual stain and have noticed what I would consider done deep or wide cracks especially in the 4×4 posts I installed. I know you mentioned no filler, leave as is and replace only if bad enough

What’s consider bad enough to replace? I’ve read 1/4” deep or wide…

Joe
Joe
2 years ago

Thanks for the quick response. This is about 3 weeks after being built…looks ok?

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Susan
Susan
2 years ago

First time staining 1 year old redwood deck. Do I do anything with the knots, some are cracking and some small ones have fallen out. Is there something I can do to keep them from falling out? Will be using RAD cleaner and brightener and semi transparent stain. Thank you.

eeroot
eeroot
2 years ago

How. Do you repatr brick that the deck is joined to

John
John
1 year ago

Have stripped and brightened a cedar deck, replaced some rotten boards, do those boards need to be left uncovered to weather or can they covered with clear plastic along with old boards until they can be stained? Is there a recommended stain to match CWF-UV cedar, don’t want to use CWF-UV again, was looking at TWP 1501.

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Zenovia Shaw
Zenovia Shaw
2 years ago

Any suggestions for splinters on the deck? From the day it was built there seemed to be numerous amounts.

James
James
2 years ago

Hi, We have a pressure treated wood deck about 10 years old now and beginning to show its age with some minor weather cracking and discoloration. I pressure wash it (fan tip only) with detergent every spring so it is “clean” but there are still plenty of stains in the wood. I’d like to put on some kind of sealer to prolong its life and hopefully improve the look a bit. The wood is expose to extreme cold and lots of snow and ice so I am concerned it will just chip and flake and make things much worse. I’d be grateful for any suggestions and advice!

Chris Chappel
Chris Chappel
2 years ago

What about taking elmors wood glue and mixing in saw dust of the type of wood you are trying to fill a crack, and making a putty to fill cracks or say spaces in shrunk treated deck wood?

Do you think that would hold up to the elements and possibly be able to be stained with the rest of my deck come the fall?

Redodesign
Redodesign
1 year ago
Reply to  Chris Chappel

What we use is construction adhesive mix with sawdust rub in cracks sand it

mark
mark
2 years ago

i have 4 x 6 supporting posts on my wood awning that have developed surface splitting( not all the way thru). what do you suggest to use on these splitting surfaces?. I want to stop any further progress of this condition. the posts and awning are about 9 yrs. old.

Kevin
Kevin
2 years ago

What do you recommend for a knot that has started to rot? I see you don’t recommend fillers but worried to just stain this area like the rest of the deck.

Any help would be greatly appreciated!

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Rox
Rox
2 years ago

What stainable product would you use to fill cracks on a deck in Maine that is exposed to extreme heat & cold?

Judie
Judie
2 years ago

The top rail in this photo has been curing for 8 months and we are now ready to stain deck- photos show what happened to board over winter. If filler is not suggested, do you have any suggestions as to what should be done? Thanks for your time and great website!

Judie
Judie
2 years ago

Thanks 4 your response, hoping pics went thru. If we replace board do we wait several months to stain or stain now with the rest of the deck? Thanks again!

Jeff
Jeff
3 years ago

my contractor filled screw holes on the deck and railing with wood filler then sanded the areas. I wanted to stain it natural, but now not sure what to do as I’m concerned these wood fill sections will be very noticeable. Should I sand the whole deck and railing to even it out then prep treat it before I stain? Would changing the stain color to a darker shade help?

Tresa Litteral
Tresa Litteral
3 years ago

Building a new deck. Should anything be done to the knots in the wood before staining deck?

Larry
Larry
3 years ago

Hello,

We have an old (likely since the house was built in 1990) untreated cedar deck, with some rot and/or softer spots on its boards.
1.) Would I be able to use PC-Petrifier Wood Hardener on some of its boards and railings? (I wouldn’t mind using on all of it.)
2.) If so, should I use it after I would clean and brighten it?
3.) I’d like to just seal it afterwards (and yearly from now on). What would you recommend as the best sealer for this type (age & condition) of deck? We live in Seattle, and even though the deck is facing west, it gets max 3hrs/day of sunlight.

Thank you very much!
Larry

glenn r grossarth
glenn r grossarth
4 years ago

I just put new decking boards on my deck, Looks really good but a lot of nail holes, I would like to fill them and stain the deck clear, question is there any filler that would look like treated wood ? so when I put the thompsons clear on my eyes won’t go right to them ? Thanks Glenn

Mark
Mark
4 years ago

I know that wood filler and caulk aren’t good options for filling cracks on deck but, I have a toddler and I’m concerned about splinters. My deck was in bad shape when we moved to this house and I have sanded it down so it’s a flush surface again. I still have cracks and some deep chips. If I just paint my deck is there anything I could use to fill the bad areas? I would replace some of the boards but it would end up being more than half the deck and I can’t get into that big of a project. Please any help you can offer would be greatly appreciated

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