How to Fill Gaps in Wood Deck

Do you have a wood deck that is starting to show its age? If so, you may be wondering how to fill gaps in wood deck. Luckily, there are a few different options available to you. This blog post will explore a few different ways to fill gaps in wood decks.

How to Fill Gaps in Wood Deck

While there are various ways to do this, the best method will depend on the type of decking material. Here’s a look at some common methods for filling gaps in wooden decks. By the end, you should better understand which method is best for your particular situation. Let’s get started!

10 Reasons That Causes Gaps in Wood Deck

1. Deck Boards Are Not Properly Sealed:

The gaps between deck boards are usually caused by the wood drying out and shrinking. The easiest way to solve this problem is to seal the deck boards with a good quality sealer.

2. Boards Were Not Installed Tightly Enough:

If the deck boards were not installed tightly enough, they would eventually start to shrink and pull away from each other, causing gaps. The best way to fix this problem is to install the deck boards tighter together.

3. Improper Storage of Decking Materials:

If you live in high humidity, the decking materials may have absorbed too much moisture before they were installed. This can cause the deck boards to swell and create gaps. To avoid this problem, make sure that the decking materials are stored in a dry place before they are installed.

4. Temperature Fluctuations:

Temperature fluctuations can cause the deck boards to expand and contract, leading to gaps. If you live in an area with severe temperature fluctuations, you may want to install a deck membrane to help protect the deck boards from the weather.

Improper Storage  Of Decking Materials

5. Poor Quality Decking Materials:

If you are using poor-quality decking materials, they are more likely to shrink and expand, which can cause gaps. Make sure to use good-quality decking materials designed to resist these changes.

6. Inadequate Ventilation:

If the deck is not properly ventilated, it can cause the boards to warp and cup, which will lead to gaps. Ensure adequate ventilation for your deck by installing vents in the roof or by using a fan.

7. Not Enough Support:

If the deck does not have enough support, the boards can start to sag and create gaps. Make sure to use spaced joists evenly and are the correct size for the deck. If you are unsure of what size to use, consult a professional. You can also use metal brackets to help support the deck boards.

8. Improper Installation of Deck Rails:

If the deck rails are not installed properly, they can create gaps that allow water to seep through. Ensure the rails are installed level and flush with the deck surface to prevent this. Use shims if necessary to level the rails. Also, use corrosion-resistant fasteners to attach the rails to the deck framing.

9. Worn or Damaged Deck Boards:

If your deck boards are worn or damaged, you can replace them easily. Start by removing the screws or nails that hold the board in place. Cut the new board to size, and then replace the old board with the new one. Next, nail or screw the new board in place. If there are large gaps between deck boards, you can fill them with wood filler. Please wait for the wood filler to dry and sand it down.

10. Uneven Settling of the Deck:

The deck may have settled unevenly over time, which can cause gaps between the boards. If this is the case, you may need to level the deck by adding shims under the low spots. You can also add support under the deck to level it out.

Use a Power Tools

10 Ways on How to Fill Gaps in Wood Deck

1. Use a Weather-resistant Wood Filler:

There are many different types of wood fillers on the market, and most of them will do the job. However, you need to make sure that you get a filler specifically designed for outdoor use. This type of filler is weather-resistant, and it will hold up better in extreme temperatures.

2. Use a Caulking Gun:

If you don’t want to buy a specific wood filler, you can always use a caulking gun to fill the gaps in your deck. Simply buy a caulk tube designed for outdoor use, and then use the gun to apply it to the cracks in your deck.

3. Use Silicone:

Silicone is another great option for filling gaps in your deck. It is weather-resistant and will bond well with the wood. Apply the silicone to the gap using a caulk gun, and then smooth it out with your finger.

You can also use a putty knife to make sure the silicone is level with the surface of the wood. Finally, let the silicone dry for 24 hours before walking on the deck or placing any furniture.

4. Mix Sawdust and Epoxy Resin:

You can mix your epoxy putty using sawdust from your deck and some epoxy resin. First, collect some sawdust from where you will be working. Next, mix the sawdust with epoxy resin in a 1:1 ratio. Once the mixture is thoroughly combined, apply it to the gap using a putty knife.

5. Pour the Mixture into the Gaps:

If you don’t want to make your epoxy putty, you can pour the mixture into the gaps. Start by mixing equal parts epoxy resin and hardener. Once the mixture is combined, pour it into the gap. Use a putty knife or other tool to push the mixture into the gap, then smooth it out.

Use a Weather Resistant Wood Filler

6. Let the Epoxy Hardens:

Once the epoxy has been applied, it will need to harden. This usually takes 24 hours but may take longer depending on the temperature and humidity. Once the epoxy is hard, it can be sanded, stained, and sealed like the rest of the deck.

7. Apply Stain or Sealer:

To finish filling the gaps in your wood deck, apply a stain or sealer. This will help protect the wood from the elements and will help to keep it looking its best. You can find these products at your local hardware store or online.

8. Use a Foam Expansion Strip:

If you have a gap too wide to fill with caulk or epoxy, you can use a foam expansion strip. This is a thin piece of foam that will expand when it comes in contact with water. It is easy to install, and it will fill the gap nicely.

9. Use a Nail Gun:

If you have a nail gun, this is a perfect solution for filling in the gaps. First, put some wood glue in the gap, then use the nail gun to shoot nails into the sides of the boards and close up the gap. Ensure to countersink the nails below the surface, so they don’t snag your feet.

10. Install a New Deck Board:

If the gap is more than 1/4 inch wide, you may need to install a new deck board. Cut a new board to size, then use a hammer and chisel to remove the old board. Please make sure the new board is the same thickness as the others so it will fit in the groove. Finally, nail or screw the new board into place.

Use a Foam Expansion Strip

Some Helpful Tips and Suggestions

Here we have given some tips on how to fill gaps in wood deck.

1. Inspect the gap to see whether it is a tight or loose fit. A gap that is a tight fit can be filled with wood putty, but a loose fit will need something more substantial, like caulk or construction adhesive.

2. If the gap is wider than 1/4 inch, use wood putty to fill it. If the gap is narrower than 1/4 inch, use caulk.

3. Choose a putty or caulk that closely matches the color of your deck.

4. To apply wood putty, knead the putty until it is pliable, then press it into the gap. Use a putty knife to smooth out the putty and remove any excess.

5. To apply caulk, cut the tip of the caulking tube at a 45-degree angle. Insert the tube into the gap and squeeze the caulking gun until the caulking comes out of the tube. Use a damp finger to smooth out the caulk and remove any excess. Let the caulk dry for 24 hours before walking on the deck.

6. If you are using construction adhesive, apply it to the sides of the gap with a caulk gun. Press the boards together and hold them for 24 hours while the adhesive dries.

7. Once the putty or caulk has dried, sand the area smooth with a fine-grit sandpaper. Vacuum up any dust, then apply a deck sealer or stain to protect the wood.


Deck repair can be a daunting task, but with the right tools and some careful planning, you can have your deck looking good as new in no time. We hope this article on how to fill gaps in wood deck has helped give you an idea of what’s involved in repairing your deck and shown you that it’s not as difficult as it may seem.

If you have any questions or need help getting started, don’t hesitate to reach out to us. We love helping our customers get the most out of their decks! Have you tried filling gaps in your wood deck? What method did you use? Let us know in the comments below!

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