Can I Use Wood Filler for Decks? 4.4/5 (71)

This post was updated on June 14, 2024

Hi, I am Scott Paul. I have been staining new and old decks for over 30 years. My Wood Filler help tips for decking are based on my history as a wood restoration contractor and actual hands-on testing. See here for more info about me.

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. However, as the Internet’s top authority on wood deck restoration, I do not recommend using wood filler or caulk for your decking projects. However, we are always interested in hearing about your deck restoration experiences. If you’ve tried using wood crack filler on your deck or are thinking about doing so, please leave me a comment or question below.

Wood Filler Deck

Wood Filler for Decking

See Below For Commons Question on Deck Wood Fillers

What Is the Best Exterior Wood Filler for Decks?

My Pro Tip: There isn’t one.

We can’t recommend caulk and wood filler products to fill cracks in a deck. Using wood filler for decks will not yield a good result. Decking stains that show the wood grain will not blend with a wood filler. The filler will stand out and look like “white” blotches over your deck.

White Blotches Wood Deck Filler

Should I Fill Cracks in Deck Boards?

No, it’s best to leave cracks as they are. They won’t harm 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 it is used in when used on wooden decking. This is especially true in an area with 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 have 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, 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 stain over wood filler, use a solid stain. A semi-transparent stain will not hide it, and no stain will do a perfect job of covering it, but a solid stain will work best.

What Can I Do About Deck Cracks?

My Pro Tip: Leave them alone. They are normal and will not harm the deck.

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 or turning the boards over may be the best option. But cracks aren’t detrimental to the deck in many cases, 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 using wood filler to repair rotted wood, it would be better to replace the wood in most cases.

Can I Use Wood Filler on Pressure-Treated Wood?

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

I have Cracks in My Deck Support Posts. Should I Repair?

Cracks In Deck PostIt’s not an issue! Deck support posts are made of pressure-treated pine, and pine wood generally shows cracks after a few years outside. This is completely normal, and your deck support structure will not have any issues.

Need Help? Wood Filler Deck Questions?

Want Help? Please ask me below if you have questions about my deck tips with a wood filler or need help choosing a stain. Just post a comment below and include as much information as possible.

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
1 year 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.

Debbie Smith
Debbie Smith
1 month ago

Have large chips at eyes. Big enough if you catch right barefooted can cut you. What can I use to fill? Or should deck company replace any boards like this?

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Tim
Tim
5 months ago

the 2×8 top rail on my exterior deck has separated about a1/4″, what can i use to fill it in?

david
david
6 months ago

Love your page Scott and thank you for this service!

OK so we have painted deck and the last time it was painted they did a terrible job and painted way too thick and didn’t allow proper drying time, etc. We are redoing it and looking to make it decent – not perfect.

We rented this sander and it’s going an OK job – we wish it could get more off but I think that if it were more intense then the exposed nails (or like all of the nails) would be an issue so doesn’t seem feasible. Also we have no problem replacing bad boards – they are pressure treated and we even have some left over from the last time ~3 years ago and they are ready to go

  1. We are planning on repainting the same color – but
  • Looking for advice on how we are doing and how much more to sand? – if just re-painting no need to chemical strip or anything radical like that right?
  • Suggestions for sanding/ stripping the rails with the detail and the bubbling paint
  • We will replace the worst of the boards – still no filling even with paint ?
  • Use nails for the new boards or deck screws? Please recommend w/ specifics
  • Prime before painting? New boards? All boards? No boards?
  • Paint recommendation? Please recommend w/ specifics – we will have it color matched

Anything else to keep in mind?

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Joshua Hillman
Joshua Hillman
6 months ago

I’m planning to repaint my moms wood deck, but should I treat it with something after a thorough cleaning and sanding?

lee
lee
11 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
1 year 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
1 year ago

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

Andy
Andy
1 year ago

Attached is a picture from my previous question

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Andy
Andy
1 year 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 year 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 year ago

Thank you in advance.

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Donna
Donna
1 year 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.

Jerry
Jerry
7 months ago
Reply to  Donna

Painting contractor here. In answer to your second question: If you can avoid painting anything outside, do it. Yes, stripping the paint from your exterior window trim and coating it with a solid stain (oil base or water-miscible oil) will make future maintenance much easier. The stain will not peel.

Joe
Joe
1 year 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?

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