Can I Use Wood Filler for Decks? 4.4/5 (67)

This post was updated on July 1, 2023

Wood 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 Ranger Patch 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!

Please Rate This. You may also post comments or ask questions below.

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Chani
Chani
2 months ago

I am so grateful for this website and for your frank, clear answers to questions I’ve had for years. I’ve tried wood filler before- epic fail. You are spot on. I will say that I used Gorrilla Glue for a huge, deck splinter a few years ago and, while not ‘pretty’, most people don’t notice and it is still working fine.

Andy
Andy
6 days ago

Attached is a picture from my previous question

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Andy
Andy
6 days ago

I am replacing old wood on my deck. The joists have some splits about 1/2″ deep and small old holes that are soft/turning black. Before replacing planks – I am thinking of spraying some boric acid to prevent any rot; and filling cracks and old holes with a loctite PL MAX construction adhesive to keep water from pooling in the voids. The loctite product appears to be very strong and used in marine applications. Any thoughts?

Marlon
Marlon
1 month ago

Hi
I have wood beams on my front and back porch. Some of the beams have long cracks in them
Im not sire if they are natural of have been caused over time by the weather.
Someone suggested i fill in these cracks with wood filler. Before doing so i wanted to ask your opinion. I have attached a pic

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Donna
Donna
1 month ago

Thank you in advance.

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Donna
Donna
1 month ago

1) 45 yr old deck exposed to extreme temperatures and snow and apparently multiple attempts painting it. Most has peeled from floor but posts have cracking and peeling paint. Want to remove rest of paint and protect wood. What is best approach? Sealing it? Waterbased or oil based stains best? Want to insure against future peeling!

2) Paint has peeled from very old, dry wood exterior window trim. Would solid stains work better than frequently re-painting? If so, waterbased or oil?
Thank you in advance. Have received many suggestions with little agreement.

Joe
Joe
1 month ago

Have a screens in deck . The screening is framed, there is a gap between one of the uprights and the screening. Just had the deck refinished and the new contractor says that he can’t recaulk the space. Any suggestions?

Patricia Crocker
Patricia Crocker
2 months ago

New composite deck has dark marks from filler that was used ,how can I get rid of it

Barbara
Barbara
4 months ago

For this 40-year-old, no maintenance
de ck should I use oil base primer?
And oil base stain and paint?

I am new to all these. Thank you for your help.

Barbara
Barbara
4 months ago

Best website ever.

My deck is 40 years old, lack of maintenance. Lots of rotten wood. But base is good. Have rotten knots too and big holes. What to do?

Use wood hardener?

Use primer?
Can I use primer over some leftover paint from five six years ago?

Then stain?

Then paint?

Please recommend brands too.

Appreciate your advice and time.

Thank you

Barbara
Barbara
4 months ago

Attached are four. More to come

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swd
swd
4 months ago

Permafill by Gulf Synthetics is discontinued. No longer available.

BRIAN
BRIAN
4 months ago

MANY EPOXY FILLERS STATE THEY ARE STAINABLE. ARE YOU SAYING THIS IS A LIE?

Karen
Karen
5 months ago

Hello,
I have pressured wood on my deck. The previous owner had painted the deck and it has peeled off, there is also algae and some mold.

1.Can I just sand the deck?

2 I want to use a black solid stain, is a brightener needed?

3. There are some stains that have sealants, can I use that or do I need to use a specific waterproof sealant first and then stain it?

4.In one of the panels, the end is lifted, just used a screw?

Thank you for your time.

Paul
Paul
9 months ago

So Bondo and or pro bond by Elmer’s you claim is not needed for deck repairs do nothing is your opinion. Their claims are what false?

Mark
Mark
11 months ago

Scott,
Regarding filling knot holes etc., the guy at the store suggested epoxy. No disrespect; but I had to ask.
Thanks!
Mark

Paul
Paul
9 months ago
Reply to  Mark

I read the same thing youtube

Levi
Levi
1 year ago

In one breath you say you can’t recommend a filler in the article, In the next breath you’re recommending Permafill by Gulf Synthetics (which they no longer sold BTW) in the comments. Sounds like you trying to sell a service to me.

bruce millar
bruce millar
1 year ago

I have used woodfiller for last three years on my deck and I have found the woodfiller has lasted for a year or more,I have painted the deck after I did any scrapping and sanded it .

Ed Horst
Ed Horst
1 year ago

I have a new deck that has cedar posts and beams that were assembled with Simpson “concealed” connectors. But those require 5/8″ holes where the steel pins are driven into the internal connectors. My plan was to use a plug cutter to make plugs out of the same wood to cover the holes, but the holes don’t have pristine edges. I was thinking about filling them and sanding them flush until I found this article. Any suggestions? Unfortunately, the stain we’re using is oil-based and transparent.

Ed Horst
Ed Horst
1 year ago

Thanks for the reply.

Right this second, I’m trying an experiment of the old trick of glue mixed with wood sawdust.

Perhaps the thing that will help is that the holes in question are either 9′ in the air or down by my ankles.

Pline
Pline
1 year ago

Hi there. This is all really helpful, especially seeing that the vertical cracks are normal. Here’s where I need some reassurance: I live in a place where we get ice in the winter. I kept thinking I needed to fill the variety of cracks so that the expansion of frozen water within those cracks would not worsen the condition of the wood. Is that a concern or are you saying no, it either won’t do much damage or it will do damage but there’s not much to be done about it and eventually replacement would just have to happen? I appreciate your time. Thanks so much.

Kris
Kris
1 year 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
1 year ago

Even when it looks like this?

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Alice
Alice
1 year ago

how can I restore this deck?

Linda
Linda
1 year 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 year 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 year 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
1 year 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
1 year 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
2 years 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
2 years 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
2 years ago

Thank you for your feedback!

Kelli
Kelli
2 years 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
2 years 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 2 years ago by Kelli
Connie Crogal
Connie Crogal
2 years ago

What about a epoxy filler?

Harjeet
Harjeet
2 years 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
2 years 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
2 years 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
2 years ago

And no wood cleaner as well? Thanks much!!

Ed
Ed
2 years 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
2 years 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
2 years 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
2 years 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
2 years 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
2 years 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
2 years 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
2 years 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
3 years 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
3 years ago

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

Darren
Darren
3 years ago

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

Darren
Darren
3 years ago

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

Darren
Darren
3 years ago

Thanks

Michelle
Michelle
3 years 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
3 years ago

Very helpful info on this site. Thank you!

Stefano Angelo
Stefano Angelo
3 years 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
3 years ago

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

Stefano Angelo
Stefano Angelo
3 years ago

Thanks

Jonathon
Jonathon
3 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
3 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
3 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
3 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
3 years ago

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

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Susan
Susan
3 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
3 years ago

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

John
John
3 years 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
3 years ago

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

James
James
3 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
3 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
3 years ago
Reply to  Chris Chappel

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

mark
mark
3 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
4 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
4 years ago

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