How to Fill and Sand Wood Properly

Filling and sanding are the foundation of a good finish. Rush them and the final result shows it. Here's how to do both properly.

Types of Wood Filler

Water-Based Fillers

Easy cleanup, low odour, quick drying. Good for small holes and cracks. Takes stain moderately well.

Solvent-Based Fillers

Stronger, more durable. Better for larger repairs. Stronger smell, needs ventilation.

Two-Part Fillers

Mix resin and hardener. Very strong, very durable. For structural repairs. Doesn't take stain well.

Grain Filler

For filling open grain (oak, ash) before finishing. Not for holes - for creating smooth surface on open-grained wood.

Choosing the Right Filler

• Painting over? Any filler works - colour doesn't matter.
• Staining? Match filler to final wood colour or use stainable filler.
• Clear finish? Very difficult to hide - try to avoid needing filler.
• Outdoor use? Use exterior-rated filler.
• Large voids? Consider epoxy or two-part filler.

Filling Technique

Preparation

1. Remove loose material and debris from the hole
2. Sand immediately around the area
3. Remove dust

Application

1. Press filler firmly into the hole with a flexible scraper
2. Overfill slightly - filler shrinks as it dries
3. For deep holes, fill in layers, letting each dry
4. Smooth surface as much as possible before it sets

Drying

Let dry completely before sanding. Times vary by filler type and depth. Don't rush - sanding undercured filler makes a mess.

Sanding Basics

Grit Progression

Always work through grits progressively:

• Start with grit that matches the surface condition
• Don't skip more than one grit step
• Each grit removes scratches from the previous
• Finish at appropriate grit for your final finish

Example progression: 80 - 120 - 150 - 180 - 220

Sanding Technique

• Sand with the grain, not across it
• Use consistent pressure
• Keep the sanding surface flat (don't round edges unless intended)
• Check progress by wiping with mineral spirits - shows scratches and flaws

Power vs Hand Sanding

Power sanders are faster but remove material quickly - easy to over-sand or create dips. Hand sanding offers more control for final stages.

Combination approach: power sand up to 150-180, hand sand final grits.

Browse our sanders range.

Sanding Filled Areas

1. Start with grit that matches surrounding surface
2. Sand filler level with surrounding wood
3. Continue with normal grit progression over entire surface
4. Blend filled area into surroundings

Common Mistakes

• Not filling deeply enough (shrinkage leaves depression)
• Sanding before filler fully cured
• Skipping grits (leaves visible scratches)
• Sanding across grain (scratches show through finish)
• Over-sanding thin layers (sanding through to substrate)
• Not removing dust between coats/stages

Quality Check

Before finishing:

• Wipe with mineral spirits or water (shows defects)
• Check in good light at low angle (reveals scratches)
• Feel with hand (catches rough spots eyes miss)

Find sanding supplies in our sanding accessories and abrasives collections.