How to Repair an Old and Damaged Wooden Deck With Wood Filler?

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By Alexandra Miller

Updated: Mar 11, 2024

8 min read

Wood Filler for Decks
Photo: Decks Docks

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    Wood fillers can repair the ongoing swelling and shrinking of deck planks caused by weather exposure. It is crucial to select an exterior-grade wood filler that matches the deck coating's color and is designed to withstand outdoor conditions.

    Wood Blender and Wood Tone Putty, both of which offer various colors to match different stains. Proper application involves filling the cracks in stages, allowing sufficient drying time, and sanding the surface smooth. It's essential to understand that using wood filler on decks is a temporary solution requiring regular maintenance, as the filler may need to be reapplied every six months. Ultimately, choosing the right wood filler for your deck involves considering factors such as compatibility with the deck coating, exterior use designation, color-matching ability, and durability in outdoor conditions.

    Also Read: The 4 Essentials To Building A Deck In Coons Rapids Minnesota

    Evaluate the Necessary Repairs Needed

    Beginning any repair project involves evaluating the extent of the damage. Examining the boards on your deck will provide insight into the issues that require attention. While imperfections like knotholes and wood decay can often be remedied with wood filler, severe warping, lengthy cracks, or a completely broken piece of lumber may necessitate alternative solutions. If the damage is extensive, replacing an entire board might be the most appropriate course of action.

    Choosing the Right Wood Filler

    Choosing the Right Wood Filler for Deck
    Photo: Fine HomeBuilding

    Opt for a wood filler produced by the same company as your deck coating. Ensure it's suitable for outdoor use. Verify that it can match the color of the deck.

    Matching With Your Deck Coating Manufacturer

    When restoring a deck, it's essential to find a wood filler from the same manufacturer as your deck coating. For instance, when using decking oil or deck stain, rely on their respective exterior wood fillers tailored for outdoor use. What's convenient is that these fillers come in various colors to match different stain shades. Ensuring compatibility, as the filler is likely tested with the stain, is crucial. This approach will make sure to choose the right wood filler.

    Wood Filler for Outdoor Applications

    Choosing the right wood filler for outdoor projects is crucial to avoid premature deterioration. Using an indoor filler instead of an exterior one will likely lead to early failure due to its lack of durability and UV resistance. Sun exposure can cause the indoor filler to shrink and dry out quickly. Therefore, verify that the filler is labeled Exterior Use before application.

    Deck Stain Integration

    Ensure the filler blends with the deck stain to conceal any gaps. Certain fillers may not absorb the stain, leading to a mismatched appearance. Opt for a wood filler from the same manufacturer as your deck stain for a precise color match. Verify that the filler is formulated to absorb the stain for a cohesive finish.

    Repairing Gaps in Your Wooden Deck

    It is a straightforward task. Each product comes with specific instructions, but here's a general approach.

    Repairing Wooden Deck using Wood Fillers
    Photo: Amazon

    Use a flexible blade or scraper to apply the filler to the cracks, filling them in stages of about 10 mm and allowing 2 hours for drying between applications. Wetting the blade slightly can facilitate the process. For filling thin timber grain, dilute the filler with water. Smooth the filler using the damp blade, remove any excess with a sponge, and let it dry before sanding for a smooth finish.

    Additional Suggestions Wood Filler for Decks

    Here are some additional suggestions for using wood filler on your deck. Many fillers may not blend well with transparent or semi-transparent stains, so consider using an opaque deck stain to conceal the filler completely. Keep in mind that fillers on high-traffic decks may crack and dislodge within a few months. While some fillers may last up to 12 months, many deck owners have found them ineffective and costly in the long run. Treating outdoor timber, including filling cracks, is an ongoing maintenance task similar to staining decks periodically.


    Using wood filler to mend a deck is possible by opting for an exterior filler suitable for outdoor use, easy to sand and compatible with painting or staining is the ideal choice for deck repair. It is important to sand the deck before applying filler to avoid a rough surface and prevent the peeling of the stain.

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