Can I Use Wood Filler for Decks?  4.4/5 (68)

This post was updated on May 1, 2024

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.

author avatar
Scott Paul ~ Restoring Wood & Decks Since 1993 Owner
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.

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Chani
Chani
10 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.

lee
lee
2 months ago

I’m redoing our deck. The wood, under 3-4 layers of paint, doesn’t look to bad to me. My wife really likes the look with the paint partly on the wood too. My question is what would be my best option for keeping the paint partly on and treating it. I am leaning toward Penofin oil for treated wood. It’s a covered deck but still gets a little wet. Please tell me what you think

Thanks,
Lee

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hattie
hattie
6 months ago

Does drylok work with wooden deck? Our deck is 10 years old with deep cracks on the supporting columns. Our contractor suggested 1 layer coating of drylok to fill the cracks and waterproof them from further water damage. The deck is solid dark brown color now. Thank you!

ernest mungo
ernest mungo
6 months ago

my deck has splinters
,i was wondering if i could sand it and seal it,rather than replace it

Andy
Andy
7 months ago

Attached is a picture from my previous question

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Andy
Andy
7 months 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
9 months 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
9 months ago

Thank you in advance.

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Donna
Donna
9 months 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
9 months 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
10 months ago

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

Barbara
Barbara
11 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
11 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
11 months ago

Attached are four. More to come

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swd
swd
11 months ago

Permafill by Gulf Synthetics is discontinued. No longer available.

BRIAN
BRIAN
11 months ago

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

Karen
Karen
1 year 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
1 year 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
1 year 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
1 year 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
2 years 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
2 years ago

Even when it looks like this?

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Alice
Alice
2 years ago

how can I restore this deck?

Linda
Linda
2 years 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
2 years 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
2 years 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 years ago

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

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