Wood Filler vs. Wood Putty: What's the Difference? (2024)

When it comes to filling holes, gaps, and other imperfections in wood, you have a choice: wood putty vs. wood filler. The two products may seem similar and the terms are often used interchangeably, but they serve specific purposes and bond differently when used on unfinished or finished wood. Read on to learn the key differences between wood putty vs. wood filler to help you determine which product is right for your project.

Wood Filler vs. Wood Putty: Key Difference

The key difference between wood filler and wood putty is that wood filler is used for unfinished wood and wood putty is for finished wood.

You can't always understand this difference by reading the manufacturer's labels because each manufacturer uses the terms filler and putty differently. Wood filler is often used as a term describing all sorts of filling agents, including wood putty, but also epoxy fillers, acrylic fillers, water-based fillers, solvent-based fillers, auto-body fillers, and more.

What Is Wood Filler?

Wood filler is a solution of fibers (typically wood byproducts) and hardening resins intended for filling imperfections in wood pieces that haven't yet been finished. Wood filler hardens quickly after application, allowing it to be sanded flush with the wood's surface.

Most wood filler is stainable, making it easy to cover imperfections filled with wood filler. Additionally, most wood filler products are available in a range of colors to better match the tone of the unfinished wood prior to staining. The stainable component in wood filler is the fibrous material, meaning the more fiber in the solution, the more easily it accepts stain. For best results, choose a wood filler that is labeled "stainable."

When to Use Wood Filler

Wood filler should be used on unfinished wood, as it won't bond well with finished wood. Here are some common uses for wood filler:

• Filling cracks and holes in unfinished wood
• Filling nail and screw holes in unfinished furniture pieces
• Filling holes in interior trim before painting or staining
• Filling cracks and gouges in wood flooring during refinishing
• Filling voids in rotten wood (after wood hardener)

Wood filler shouldn't be used outdoors because it can shrink and crack, especially during temperature fluctuations. However, there are wood fillers intended for interior and exterior use, such as some two-part wood fillers, which include special hardeners that prevent shrinking and cracking.

How to Use Wood Filler

The steps below provide general guidance but always default to the manufacturer's instructions. To use wood filler, follow these steps:

1. Clean the imperfections in the unfinished wood. If the wood is rotten or decayed, apply a wood hardener and remove any loose material.
2. Mix the wood filler thoroughly to fully incorporate the solution.
3. Smear the wood filler into the gap or hole using a putty knife.
4. Overfill the hole to account for shrinking
5. Once the specified time has passed (usually about 30 minutes), sand the wood filler flush with the material.
6. Finish the wood.

What Is Wood Putty?

Wood putty is a pliable mixture of chemicals and colorants that's intended for filling imperfections in wood items that have already been finished. Unlike wood filler, wood putty stays pliable after application. Its pliability makes it suitable for use in exterior settings where expansion and contraction are a concern.

Wood putty can't be sanded and stained like wood filler, because it lacks fibrous material. But many varieties can be painted once they fully cure. Instead of overfilling the gap, you'll need to wipe away excess wood putty after it's been applied.

When to Use Wood Putty

Wood putty is intended for use on wood that is already finished, such as with stain or varnish. Here are some common uses for wood putty:

• Filling small dents and dings on finished wood furniture pieces.
• Fixing imperfections in wood that will be subject to expansion and contraction, such as wood in exterior settings.

Wood putty can be used outdoors because it is slightly pliable and won't shrink or crack like wood filler. However, even after wood putty is fully cured, it will never be as hard as a wood filler.

One of the most common types of wood putty is a putty stick, which is essentially wood putty in crayon form. Wood putty sticks are available from several brands in several shades. They're great to have on hand for quick repairs on scratched or damaged furniture.

How to Use Wood Putty

Here's general guidance and tips for using wood putty but always defer to the manufacturer's instructions.

To use wood putty, follow these steps:

1. Clean the finished wood surface.
2. Choose a wood putty that closely matches the color of the finished wood.
3. Smear the wood putty into the gap, hole, or scratch, then rub away the excess with a soft cloth.
4. Let the wood putty cure for the specified time.

Choosing Between Wood Filler and Wood Putty

Wood filler and wood putty are both useful and valuable products to have on hand. If you need to choose which product to use, ask yourself the following questions to help you decide.

• Is the wood unfinished or finished? If unfinished, use wood filler. If finished, use wood putty.
• Do I need to sand or stain the wood? If so, use wood filler.
• Is the wood inside or outside? Wood putty is better for outdoor projects of finished wood.