How to Use Bondo Wood Filler: Step-by-Step Guide for Wood Repair

Fixing a dent or rust spot on a car instead? Wood filler isn't made for that job. See our step-by-step guide on how to use Bondo body filler for auto body repair.

Bondo Wood Filler is a two-part filler for repairing damaged, rotted or missing wood on doors, windows, trim, fences and furniture. It sets fast, sands in about 15 minutes, and can be stained or painted, indoors or outdoors. This guide covers the right mix, how to apply it, and how to get a repair that blends into the wood.

What You'll Need

• Bondo Wood Filler with its cream hardener (also in a quart and ready-mix pouches for small jobs)
• Bondo Rotted Wood Restorer, if the wood is soft or rotted
• A plastic spreader or putty knife and a clean, non-porous mixing board
• 80 grit and 180 grit sandpaper
• A tack cloth, plus primer, paint or stain to finish
• Gloves, safety glasses and a dust mask

How to Use Bondo Wood Filler: Step by Step

1. Clean the surface

Wash the area with soap and water to remove dirt, wax and oil, then let it dry completely.

2. Remove damaged wood

Sand the repair area with 80 grit to remove paint, old finish and any loose or rotted wood. Go a little past the edge of the damage so the filler grips sound wood. Brush away the dust and wipe the area with a tack cloth.

3. Harden rotted wood (if needed)

If the wood is still soft after you dig out the worst of the rot, brush on Bondo Rotted Wood Restorer before filling. It soaks in and hardens the fibers so the filler has a solid base.

4. Mix filler and hardener

Knead the hardener tube first. On your mixing board, use a 3-inch strip of hardener for a 3-inch puddle of filler; that is also the most you should mix at one time. Fold the two together until the color is even, with no streaks. Never put hardener into the can, and never return mixed filler to it.

5. Apply the filler

You have about 3 to 4 minutes before the filler starts to set. Press a thin first layer firmly into the wood, then build up in layers until the repair is slightly higher than the surrounding surface. For large missing sections, build in several layers rather than one thick one.

6. Shape and sand

Let the filler cure for about 20 minutes before shaping; it can be sanded in as little as 15 minutes. Rough-shape with 80 grit, then finish with 180 grit or finer and featheredge the edges into the wood. Fill any pinholes with a skim of Bondo Glazing & Spot Putty.

7. Stain or paint

The repair can be stained or painted in about 25 minutes. Prime before painting, and follow your paint or stain maker's instructions. Filler takes stain differently from real wood, so test the stain on a hidden spot first.

Bondo Wood Filler Tips

• Work above 45°F (7°C). Cold slows the cure.
• Mix small batches. The working time is short, so mix only what you can apply in 3 minutes.
• Clean tools right away with acetone or lacquer thinner, before the filler hardens.
• Painting over it? A painted finish hides the repair best. Stain will usually show the filler as a slightly different shade.

FAQ

How long does Bondo Wood Filler take to dry?

It can be sanded in about 15 minutes and stained or painted in about 25 minutes at room temperature. Cold weather slows it down.

Can Bondo Wood Filler be used outdoors?

Yes. It's made for both interior and exterior repairs, including window sills, doors, trim and fences. Paint or seal it afterwards to protect it from the weather.

Can you stain Bondo Wood Filler?

Yes, but it won't absorb stain exactly like the surrounding wood. Test on a hidden area first, or paint over the repair for an invisible finish.

What's the difference between Bondo wood filler and body filler?

Wood filler is made for wood repairs. Bondo body filler is made for metal and fiberglass, such as car dents and rust repair.

Shop fillers and Bondo wood repair products at Strobels Supply, or contact our team if you need help choosing.