How to Repair Wood and Fill Holes Like a Pro
Tackle Common Repairs with Epoxy, Adhesives & Fillers
Wood is a fascinating material to work with: organic yet rigid, with beautiful grain patterns and a natural tendency for knots, cracks, rot, and edge splits. But an imperfection doesn't mean that the piece is unusable. Whether you're a woodworker, own a wooden boat, or want to tackle DIY projects around the home, learning how to tackle common wood repairs is essential to maintaining both beauty and function. This guide will show you how to identify different issues that can occur with wood, as well as the right products and techniques for long-lasting stability.
Determine the Right Repair for Damaged Wood
Before choosing a product to fill gaps in a wood slab or fix a small defect, you should check the size and purpose of the repair. Different situations require different products.
How to Fill Cracks in Wood with CA Glue
Thin CA glue (cyanoacrylate), more commonly known as super glue, is great for small cracks or splits. This adhesive sets fast to create a quick and clean repair with little product needed. While CA glue also comes in medium and thick viscosities, you’ll want to use a thin viscosity to properly penetrate the wood grain. The adhesive flows like water to bond fibers deep within the crack to prevent further splitting.
How to Use CA Glue
- Add a few drops of your CA glue directly into the crack or along the seam.
- Wait for 30–60 seconds, depending on the CA glue you're using for the repair, to properly set. For an instant cure, we recommend using an accelerator spray.
- Once hardened, sand smooth and apply a wood stain or the final finish.
Best Uses For CA Glue
- Repairing cracks
- Stabilizing soft, punky wood
- Building models and dioramas
- Reinforcing screw/fastener holes
- Trim work and small decorative projects
- Instrument repairs
- Touch-ups on finished furniture
TotalBoat TotalBond comes in three different viscosities, including thin, so you can pick and use the one that’s best for your project.
Filling Voids and Knots with Wood Filler
Wood filler works best for medium-sized gaps, larger knot holes, and repairs where a traditional look is desired. You can make your own with CA glue and sawdust, or choose from a variety of epoxy, water, and solvent-based fillers based on your project needs. We recommend epoxy wood filler for most gap fills due to its strong bond and lack of shrinkage. Once cured, the repair can then be sanded, stained, or painted for the final look.
How to Use an Epoxy Wood Filler
- Remove loose debris or soft fibers from the void.
- If your wood filler is a two-part formula, mix and blend it until you have a uniform color and consistency.
- Press the filler firmly into the crack with a putty knife or spreader. Slightly overfill to allow for sanding flush.
- After curing (20–30 minutes), sand smooth and finish as desired.
- You can also create your own wood filler with sawdust and CA glue or epoxy resin. Simply add sawdust to your chosen medium and use as instructed.
Best Uses for Epoxy Wood Filler
Wood filler is great for fixing larger holes, rot, or missing wood. It helps you rebuild and shape the surface, not just seal it. Unlike CA glue, an epoxy wood filler like TotalBoat FixWood replicates real wood, with the ability to sand, drill, paint, stain, or varnish once cured. This makes it the best choice for both structural and cosmetic repairs.
Filling Large Cracks and Voids with Epoxy
Epoxy resin is an excellent solution for deep cracks, large gaps, and structural bonds. While ideal for repairing furniture, boat hulls, door frames, or other functional wood pieces, not all formulas offer the same benefits. Be sure to choose the best epoxy resin for your repair project based on desired clarity, strength, and resistance.
How to Use Epoxy to Fill Voids in Wood
- Clean and dry the wood thoroughly to remove any dust, oils, or moisture before you begin. If there is any rot, use a scraper or chisel to remove.
- For added stability on soft, weathered, or new/bare wood, apply penetrating epoxy resin to strengthen and seal the surface.
- Choose the right epoxy for your project: Use a deep-pour formula for large or deep voids, and reach for a structural or bonding epoxy when you need strength, adhesion, or reinforcement.
- Mix and pour at the recommended ratio: Follow the correct mix ratio for the epoxy you’re using; use this epoxy calculator to determine how much you’ll need for your project.
- Customize with color: Add tints to create unique effects, using alcohol inks, mica powders, or pigment dispersions to get the look you want
- Use a heat gun to release bubbles; allow the epoxy to fully cure according to the product’s recommended timeframe.
- Sand flush and finish as desired. For outdoor use, apply a UV-stable finish like Halcyon Varnish to help prevent discoloration.
Best Uses for Epoxy
Some repairs call for more than filling a gap, they require a material that becomes part of the structure. That’s where epoxy shines, offering strength, clarity, and durability that simpler fillers can’t match. Unlike traditional wood fillers or CA glue, epoxy can span larger areas, reinforce the surrounding material, resist shrinkage, and create a smooth, durable surface that’s ready for varnish, paint, or polish.
Penetrating Epoxy: Penetrating formulas are designed to soak deeply into soft, weathered, or porous wood. They help strengthen compromised fibers, improve adhesion for future coatings, and stabilize the surface before filling, bonding, or finishing. Use this type when the wood itself needs reinforcement before you start building up layers.
Marine Epoxy (General-Purpose / Structural Epoxy):
Marine epoxy formulas are ideal for bonding, gap-filling, and sealing small cracks or surface defects. They’re versatile, easy to work with, and create a strong, waterproof bond. This type is typically used for structural repairs, woodworking joints, laminating, and projects where durability and adhesion matter most.
Deep Pour Epoxy: Deep-pour formulas are designed for casting larger volumes in a single pour, such as deep voids, knots, or artistic fills. They cure slowly to minimize heat buildup and help maintain clarity. Choose a deep-pour epoxy when you need to fill bigger spaces cleanly without pouring multiple thin layers.
Pro Tips to Seal Cracks and Fill Gaps in Wood
- Always test your color and finish first: Apply a small amount on a hidden area or a scrap piece of the same material to confirm the tone, clarity, and final look before committing to the full surface.
- Warm epoxy gently to improve flow: Place the sealed resin and hardener bottles in a tub of warm water to lower viscosity, which helps reduce bubbles and allows the epoxy to level more smoothly.
- Seal porous woods: Apply a thin seal coat first to help prevent bubbles and curing issues.
- For wood fillers like FixWood: Overfill slightly so it will sand easily after curing.
- For CA glue repairs: Choose the viscosity that matches the size of the defect. Use thin CA glue for microcracks and hairline splits where you need deep penetration, and use medium or thick CA glue for larger gaps, knot fills, or areas that require building up material.
Above: Kneading and sculpting Fixwood into place to fill a gap in damaged wood trim.
Frequently Asked Questions
Can I use epoxy resin and wood filler together?
Yes. Many makers stabilize deep voids with epoxy first, then finish with FixWood for color matching or detail work.
Can I stain over epoxy resin?
Epoxy resin cannot be stained once cured because it hardens into a non-porous, glossy surface that prevents stains from soaking in. If you want color, add pigments or tints directly into the mixed epoxy.
Epoxy putties (such as wood-repair fillers) are different; they cure with a sandable, more porous surface that can accept certain stains, making them better suited for color-matching wood repairs.
Can epoxy be used as a wood filler?
Yes, epoxy can be used for gap-filling, sealing small cracks, and filling larger areas. Epoxy resin is an excellent solution for deep cracks, large gaps, and structural bonds. Structural or Marine Epoxy formulas are versatile and create a strong, waterproof bond, making them ideal for structural repairs and laminating.
However, dedicated epoxy wood filler, like
Can you screw or drill into cured epoxy wood filler?
Yes, you can drill and screw into certain epoxy wood fillers once they are fully cured. An epoxy wood filler like TotalBoat FixWood replicates real wood, giving it the ability to be sanded, drilled, painted, stained, or varnished after curing.
Should I seal wood before pouring epoxy?
Yes, for added stability on soft, weathered, or new/bare wood, you should apply penetrating epoxy to strengthen and seal the surface. This step helps reinforce compromised fibers and improves adhesion before you begin filling, bonding, or finishing. Sealing porous woods before pouring epoxy is also recommended to help prevent bubbles from escaping into the pour.
When should I use thin viscosity CA glue instead of medium or thick?
You should use a thin viscosity CA glue for small cracks and hairline splits where you need deep penetration. The thin adhesive flows like water, which allows it to properly penetrate the wood grain and bond fibers deep within the crack to prevent further splitting.
Medium or thick CA glue is better suited for larger gaps, knot fills, or areas that require building up material.