Installing door or window trim, baseboards, or crown molding almost always results in nail holes (and sometimes screw holes) that need filling. These might be minuscule holes created by finish nails or tiny pinprick holes caused by power brad nailers or finish nailers.
For a clean appearance, you can quickly fill in these holes before painting, staining, or otherwise finishing the trim. This is a simple project involving only a few tools (or maybe even just your finger), yet the results will help your project look truly professional.
Watch Now: How to Fill Nail Holes in Trim
Choosing a Wood Filler
There are two main types of wood filler: water-based and solvent-based. Water-based fillers have a creamy consistency and are easy to smooth on and clean up. Solvent-based fillers are sticky and oily and difficult to clean up if you wait until they dry. The advantage of solvent-based fillers is that they dry rock-hard, far stronger than their crumbly water-based counterparts.
With interior nail holes, however, you don't need the filler to be very strong at all. Also, in many cases, the filled holes will be covered with primer and paint, both of which provide some stability for water-based filler.
For wood trim that will be painted, you can use any color of wood filler, since it will be covered with paint. If the trim is pre-finished or you will finish it with stain and/or clear sealer, carefully select a color-matched filler that blends with the natural coloring of the wood. Fillers come in a few different colors to match common wood species. You can also purchase kits that include a filler base and colorants that you mix together to create custom colors.
You can use caulk to fill nail holes in painted trim, but caulk tends to be messier and shrinks more than wood filler, and it can’t be sanded smooth like filler can. If you use caulk, make sure it is labeled as “paintable,” and don’t leave a smear on the wood surface, which might show up after painting.
Is Filling Holes Necessary?
Carpenters who install trim are often called finish carpenters, suggesting that their work has a finished, polished look. When installing trim yourself, you should strive for the same level of refinement. One secret to a finished look is to hide the means of attachment—in this case, the nails that hold the trim in place. And the only way to do that is to fill the nail holes.
Relying on paint alone to hide nail holes is a common rookie mistake. Paint may seem to cover just fine when it goes on but, sure enough, the holes will be visible—in the form of tiny dimples—when the paint dries. If you’re staining or clear-sealing the wood, filler is an obvious must. In this case, it’s also important to take the time to find or mix the filler with a good color match, since the stain or sealer won’t hide it.
Equipment / Tools
- Putty knife
- Clean cloth
- Water-based wood filler
- 180- or 220-grit sandpaper
Apply the Filler With Your Finger
For most nail holes, the space to fill is so small that it is best to use your finger. Put a small dab of filler onto your index finger. Press the filler into the hole, and give it a quick swipe. Repeat, if necessary, to fill the hole completely. It's best to overfill the hole slightly, leaving a slight, smooth ridge over the area.
Apply the Filler With a Putty Knife (Optional)
Deeper or larger holes may require the assistance of a putty knife. For example, if you installed the trim with screws, or if you dimpled the wood with a hammer when driving a nail, a putty knife is better than your finger for filling a larger area and for creating a flat finished surface. Scoop up a small amount of filler with the edge of the knife, press the filler into the hole, and smooth off the top to remove excess.
Close the lid on the wood filler between applications, as filler hardens quickly. Even a minute or two is enough for the filler to begin to develop a dry skin on top.
Sand With Your Finger
One benefit of using crumbly water-based filler is that your finger can act as a type of sandpaper. After the filler has dried for about 15 minutes, sand off the crumbles and protrusions with your finger. A clean cotton glove also works well as a sanding tool.
Finish With Sandpaper
If you do a good enough job sanding with your finger, sanding down the filler with real sandpaper is almost unnecessary. But sandpaper will always give you a better finish. Using 180- or 220-grit (extra-fine) sandpaper, gently sand the filler with a few light passes. You’re just making the filled area smooth and removing excess filler from the surrounding wood. There’s no need to remove any wood.
Remove the Sanding Dust
Clean the surface with a clean cloth or a tack cloth. Do not rub hard with a tack cloth or you risk embedding the surface with wax. Once the surface is dust-free, it's ready for primer, paint, stain, or sealer.