Wood Filler: What It Is, Types, and How to Use It

What is wood filler?

Wood filler is a repair compound designed to fill holes, cracks, dents, and other small defects in wood. Most products are a mix of binders and resins with wood fibers or mineral fillers that harden into a sandable mass. Once cured, wood filler can be sanded, shaped, drilled, stained, or painted so the repair blends in with the surrounding wood.

A common point of confusion is the difference between wood filler and wood putty. Wood filler is typically used on bare wood before finishing and cures harder. Wood putty stays more flexible, is usually oil based, and is meant for use after finishing to fill tiny imperfections in already finished trim and furniture.

Common uses in DIY and home projects

Wood filler shows up across many tasks around the house:

• Filling nail and screw holes in baseboards, crown molding, and door casings
• Patching dents and gouges in furniture, cabinets, and doors
• Repairing small cracks or checks in hardwood floors before refinishing
• Leveling seams where two boards meet
• Smoothing open pores on species like oak and mahogany using a dedicated grain filler
• Rebuilding small corners or edges that have chipped off, especially with epoxy filler
• Plugging hardware holes during a hardware change on cabinets or doors

Types and variations

Understanding the main types will help you pick the right product for your project.

• Water-based wood filler

  • Easy to clean up with water
  • Low odor and fast drying
  • Sands easily and is often labeled stainable and paintable
  • Best for interior work; some formulas are exterior rated

• Solvent-based wood filler

  • Uses solvents for binding; stronger smell and longer open time
  • Can resist moisture better than many water-based options
  • Good for exterior trim if the product is rated for outdoor use

• Epoxy wood filler (two-part)

  • Mix resin and hardener to create a strong, durable filler
  • Excellent for rebuilding corners, edges, and larger voids
  • Bonds well and can be carved and sanded after cure
  • Often used for rot repair when paired with a liquid consolidant

• Stainable wood filler

  • Formulated to accept stain more like real wood
  • Results vary by brand and stain type; test on a scrap first

• Wood grain filler (pore filler)

  • Very thin paste that fills pores in open-grain woods
  • Used to achieve a glass-smooth finish on tabletops and cabinets

Always check the label for interior vs exterior use, dry time, and compatibility with your planned finish.

How to choose the right wood filler

• Match to the finish: If you plan to paint, nearly any paintable filler will do. For stain, use a stainable filler and test for color and absorption.
• Location matters: Pick an exterior-rated or epoxy filler for outdoor projects or damp areas. Use water-based products indoors for low odor and easy cleanup.
• Repair size: For shallow nail holes and hairline cracks, choose a standard water-based filler. For larger voids, edge rebuilds, or areas that see abuse, go with epoxy.
• Color matching: Many fillers come in wood-tone colors. You can also mix filler colors or tint some water-based fillers with water-based stain before application.
• Dry time and workability: If you need a fast turnaround, look for fast-drying formulas. For detailed shaping, a product with a bit more open time makes life easier.

Step-by-step: Using wood filler for a smooth repair

1. Prep the area

   • Clean out loose fibers, old finish, and dust. A utility knife or small chisel helps square up ragged edges.
   • For bare wood, sand lightly to open pores. For previously finished surfaces you plan to paint, scuff-sand to help adhesion.

2. Choose and mix

   • Stir water-based or solvent-based fillers to a uniform consistency.
   • For two-part epoxy filler, mix equal parts thoroughly until color is even.

3. Apply

   • Using a putty knife, press filler firmly into the void. Work across the grain to pack it, then level with the grain.
   • Slightly overfill to account for shrinkage during drying, especially with water-based fillers.

4. Let it cure

   • Follow the label. Small fills may be ready in 15–30 minutes; deeper repairs can take longer.
   • Epoxy typically needs 30–60 minutes to shape, with full cure in several hours.

5. Sand and shape

   • Start with 120–150 grit to knock down high spots, then move to 180–220 for a smooth finish.
   • Feather into surrounding wood to avoid visible edges.

6. Finish

   • Prime before painting to prevent flashing (sheen differences).
   • For stain, apply a wood conditioner if needed and test color. You may need a glaze or touch-up stain to blend.

Safety tip: Use gloves with epoxy and ensure good ventilation for solvent-based products.

Maintenance and storage

• Seal the lid tightly and store at room temperature to prevent drying out.
• For water-based filler that thickens, a small splash of water and a stir can revive it if the product label allows.
• Keep the container clean by wiping the rim before closing to maintain a good seal.
• Mark the purchase date; many fillers have a practical shelf life of 1–2 years once opened.

Common mistakes to avoid

• Using filler as a structural fix: Filler is for cosmetic repairs. Replace or reinforce rotten or severely damaged wood rather than relying solely on filler.
• Applying indoor-only filler outdoors: Moisture and UV exposure will break it down. Choose an exterior-rated or epoxy product.
• Sanding too soon: If the filler gums up the sandpaper, it is not ready. Allow more dry time.
• Expecting a perfect stain match: Filler absorbs stain differently. Pre-tint or use touch-up stain and accept that very close, not perfect, is realistic.
• Skipping primer under paint: Unprimed patches can flash through the topcoat.
• Not overfilling: Most fillers shrink a little. A slight crown ensures a flush surface after sanding.
• Using wood putty on bare wood: Putty is for already finished surfaces; it can interfere with stain adhesion.

Practical examples

• Nail holes in trim: Use a water-based filler that matches the trim color. Overfill slightly, sand flush, prime, and paint. For prefinished trim, use color-matched putty after painting instead.
• Cabinet hardware change: After moving handles, fill old screw holes with stainable filler if staining, or any paintable filler if painting. Sand, spot-prime, then finish.
• Repairing a chewed door edge: Shape the area, treat any soft fibers, then rebuild with a two-part epoxy filler. After curing, sand to profile and paint.
• Oak tabletop finishing: Apply a dedicated grain filler to fill pores, sand smooth, then stain and topcoat for a glassy surface.
• Exterior window sill spot repair: Consolidate lightly weathered wood with a wood hardener if needed, fill with exterior-rated epoxy filler, sand, prime with an exterior primer, and paint.

Related terms

• Wood putty: Flexible filler for use on finished wood, applied after staining or painting.
• Grain filler (pore filler): Thin paste to fill open pores for a smooth finish.
• Spackling compound: For drywall, not wood; it tends to crack on wood movement.
• Wood hardener: Penetrating resin that stabilizes punky wood before epoxy repairs.
• Caulk: Flexible gap sealer for joints and trim transitions, not for sanding or staining.

With the right product and careful prep, wood filler helps create clean, durable repairs that disappear once you sand and finish the surface.