What Types of Wood Repair Filler to Use

There's a filler for every wood-repair project.

There's a filler for every wood-repair project.

Whatever kind of wood you're patching and wherever it is, there's a filler for the job, and you can avoid problems by choosing the right one. Some fillers aren't for exterior use and won't last outside, others lack pliability and workability needed for certain small jobs, while others are too soft and pliable to provide much more than cosmetic repairs. The consistency and strength of the filler you use is as important as its color.

Latex- and Solvent-Based Fillers

When small gaps or holes appear in interior cabinets or hardwood flooring, a latex- or solvent-based filler is usually enough to patch them. These fillers come pre-colored so you can choose a tone that matches the woodwork. They sand easily, so you can apply them with a putty knife and remove the excess easily after they dry, and they accept finishes. Usually available in small cans, pre-mixed wood fillers don't have much structural strength. They won't hold a screw or a nail and will crack or sink if you use them to patch a hole larger than 1/2 inch in diameter.

Epoxy Fillers

When you need a filler with more structural integrity, perhaps to fill a widening crack in a floorboard or a rotted void in a door jamb, use epoxy-based filler. It comes in a tube or a can and can be clear or colored. You must apply it with care, keeping the excess to a minimum, because it doesn't sand off easily. It forms a repair that is usually stronger than the wood itself. You can drive screws into it, but it has a plastic appearance that only fleetingly resembles wood. Use it indoors or out when structural integrity is more important than appearance.

Exterior Wood Filler and Caulk

Exterior cosmetic patching jobs need a filler that resists moisture and expands and contracts with the weather. Exterior wood filler, which comes in cans, has elastomeric properties so it fulfills these conditions. Apply it with a putty knife and paint over it, if desired. Acrylic latex and butyl caulk are also weather-resistant and paintable, and because they come in tubes that fit into a caulking gun, they are good options for filling long cracks in siding and gaps between boards. Silicone caulk is highly weather resistant and pliable, but choose one with a matching color, because it isn't paintable.

Homemade Fillers

Woodworkers unable to find a filler to match the wood on which they are working sometimes resort to making their own. They mix sawdust or shavings from the wood with a little lacquer, knife it into the hole they are filling and sand it flat. It's a good cosmetic solution, but this type of filler isn't very strong and isn't suitable for large holes. An alternative is to mix sawdust with carpenter's glue. Glue makes a stronger filler, but it darkens the wood appreciably, so that the repair seldom disappears completely. Moreover, glue is harder to sand than lacquer.

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