How To Fix Gaps In Baseboard Corners?

Do you have an annoying gap at the corner of your baseboards, and you want to know how to get rid of them without removing your baseboards? You’ve come to the right place, for we have researched this question, and we have the answer for you.

Here are the summarized steps to fix the gaps in the outside corners of your baseboard:

  1. Fill the gaps with wood filler or a drywall joint compound.
  2. Scrape off the excess compound and let it dry.
  3. Sand the area by hand.

We have the more detailed steps in the succeeding sections, including preparation steps. We also have the steps for fixing the inside gaps in the corners of your baseboard. Read on!

Mans hands putting white baseboard - How To Fix Gaps In Baseboard Corners

How to fix gaps in baseboard corners?

We will start with fixing the outside gap in the baseboard corners in this section. The following section includes steps to fix the inside gap in baseboard corners.

Materials that you will need

  • Wood primer
  • Paintbrush
  • Wood filler
  • Caulking knife (2-inch and 5-inch wide)
  • Tile sponge
  • Bucket of clean water
  • 150-grit sandpaper
  • Painter’s tape

The Minwax stainable wood filler is available on Amazon. Check it out through this link.

Preparing the area to be filled

Baseboards are usually pre-primed when you buy them. Skip this section if your baseboards are pre-primed. However, if your baseboards are not pre-primed—they will look like bare wood—brush on some wood primer and leave it to dry.

Filling outside corner gaps

Detail of corner flooring with intricate crown molding and plinth.

There are two types of corner gaps—outside corner gaps and inside corner gaps. Outside corner gaps are the gaps that you see between two baseboards at the corner of a wall that is angled outward.

  1. Attach some painter’s tape along the floor where you will apply the wood filler. This is to prevent the wood filler from getting onto your floor.
  2. Place some wood filler on the larger caulking knife. Transfer a small amount of wood filler to the smaller caulking knife.
  3. Apply the wood filler to the corner by rubbing it off the caulking knife and scraping it onto the corner baseboard. Add more wood filler once you’ve rubbed off the wood filler from the small putty knife onto the corner gap.
  4. Keep repeating steps 2 and 3 until you have filled the corner gap with wood filler.
  5. Slowly scrape off the excess wood filler using your caulking knife starting from the bottom of the baseboard. Rest the edge of the caulking knife flat against the surface of the baseboard, then move it upward, scraping any excess wood filler off.
  6. Wipe the excess wood filler off and do the same thing on the other side of the corner until you’ve made a right-angled fill on the gap.
  7. Leave the wood filler to dry overnight. This will give it time to dry and shrink.

Sand off excess wood filler

  1. Check the wood filler if there is any shrinkage or cracks before proceeding. Refill and allow these areas to dry.
  2. Use the 150-grit sandpaper for sanding off any excess wood filler on both sides of the baseboard if there is no more shrinkage or gaps. Keep sanding until you get an even and smooth finish along the sides.
  3. Lightly sand the corner of the baseboard. Sand it just enough to remove the sharp corner and make a slightly eased edge. Baseboard corners that are too sharp can easily get chipped off when a hard object hits them. The slightly eased edge will help make it last longer and hold paint better.
  4. Remove the painter’s tape from the floor and get rid of any dust left by the sanding. Use a slightly moist sponge to wipe off the dust from the floor. The moist sponge prevents the dust from flying off because it attaches to the sponge. Rinse the sponge on the bucket of water and repeat as necessary.
  5. Prime the corner before applying paint. The corners with wood filler will stand out—looking slightly shinier—after you paint the baseboard if you do not prime the corner first.

Mans hands putting white baseboard.

How to fix inside gaps in baseboard corners?

Inside gaps of baseboard corners can happen to baseboards installed along the corner of two walls angled inward.

You will need the same materials that you used for fixing the outside gap minus the caulking knives, sandpaper, and wood filler. We will be using an acrylic latex caulk—with a caulking gun—instead of a wood filler for the inside gap.

Follow the same steps you used to prepare the outer gap area.

The Red Devil Lifetime Ultra 230, a premium elastomeric acrylic latex sealant, is available on Amazon. Check it out through this link.

Fixing the inside corner gap in a baseboard

  1. Use the caulking gun to apply a line of acrylic latex caulk on the inside corner gap. The tube's opening should be of the same size as the gap you will fill, and you should cut the tip at a 45-degree angle. The angled opening will allow you to insert part of the tip into the gap and apply the caulk directly into the gap. Start applying the caulk from the bottom of the baseboard and slowly move upwards until you’ve covered the gap with the caulk.
  2. Moisten your finger and use it to push the caulk into the gap. Start from the bottom and slide your finger upward to the top of the baseboard corner.
  3. Wipe or rinse off any excess caulk on your finger and continue as needed.
  4. Check the corner for gaps. Fill these gaps with caulk and push the caulk once more with your finger.
  5. Moisten the tile sponge with water and use it to wipe off the excess caulk from the inside corner. Repeat this step until you have removed all excess caulk from the inside corner.
  6. Leave the caulk to dry overnight. Like the wood filler, this is to give it enough time to dry and shrink.
  7. Check the caulk for shrinkage. Reapply caulk on any shrunken areas and repeat the caulk application steps.
  8. Prime the caulk before painting.

Should baseboards be caulked?

Mans hand caulk skirting board with caulking gun and silicone cartrige. Fill gaps in base board

Yes, they should be. Caulk naturally breaks down over time—like every other material. On average, you should re-caulk your baseboards every five to six years.

Caulk is flexible enough to adapt to expansion or contraction between the floor, walls, and baseboard. It creates a waterproof seal that prevents spilled water from entering any unprotected wood and causing rot or mold growth.

Any gap on your baseboard is an entry point for insects that can nest and damage your home's structure. If you do not caulk your baseboards to prevent infestation, you welcome insects entering the walls.

How to fix gaps between baseboards and the floor?

Silicone sealant. Man's hand of Construction worker use gun silicone tube.

Gaps between the baseboard and the floor sometimes appear when the floor joists underneath the floor start to sag. A gap will also develop between the floor and the baseboard when the house's foundation starts to sink.

In any case, gaps that are less than a quarter of an inch wide can be filled with caulk. Anything larger than this should be sealed with shoe molding first, then caulk.

Latex caulk is best for fixing gaps between the baseboard and the floor because you can paint over it. Do not use silicone caulk because the paint will easily peel off from the surface of silicone caulk.

Applying caulk on the gap

  1. Trim the tip of the caulk tube diagonally at a 45-degree angle.
  2. Insert the tip of the caulk tube into the gap and use the caulk gun to apply the caulk into the gap. Apply a steady stream of caulk into the gap.
  3. Moisten your finger and use it to push the caulk into the gap. Start from one end and slide your finger to the other end while pushing the caulk further into the gap.
  4. Take a moist tile sponge and wipe off the excess caulk. Start from one end of the gap and slide the tile sponge to the opposite end of the gap. Repeat this step until you’ve removed all the excess caulk from the baseboard and the floor.
  5. Leave the caulk to dry overnight.
  6. Check the caulk for gaps and shrinkage. After completing the steps, reapply caulk on any shrunken areas.
  7. Prime the caulk to prepare it to be painted.
  8. Paint the caulk to match the baseboard color.


Detail of corner flooring with intricate crown molding and plinth.

Fixing the gap in baseboard corners can be a simple DIY when you have clear instructions on how to do it.

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