How to Caulk Baseboard Gaps

Caulking Baseboards to Seal the Gaps

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Project Overview
  • Working Time: 1 - 2 hrs
  • Total Time: 3 - 4 hrs
  • Yield: One room
  • Skill Level: Beginner
  • Estimated Cost: $10 to $20

Many homes have baseboards with gaps either at the top, where the baseboard meets the wall, or the bottom, where the baseboard meets the floor. Such gaps are not just unattractive; they can also allow drafts to enter or heat to escape.

One easy and effective solution is to caulk the baseboards, though this is not a panacea for all gaps. If baseboard gaps are substantial, then caulking may not be as effective as replacing shoe moldings, baseboard moldings, or both.

Gaps between the bottom of the baseboard and the floor usually occur because floor joists sag and foundations settle over many years. In some cases, these gaps are wide enough that they allow air infiltration and can seriously impact your home's energy consumption. A bead of caulk applied at this joint is an easy way to block such air gaps.

Gaps at the top of the baseboard occur because the molding does not hug the wall close enough, which is common in older homes where the walls may not be perfectly flat. Even in newer walls, you may find gentle curves that create irregular gaps along the tops of the baseboards. These gaps are more about aesthetics since air infiltration or heat loss is more likely to occur at the bottom of the baseboard, where it meets the floor. You can make the wall look smoother by running a continuous bead of caulk along the top of the baseboard, where it meets the wall.

Tip

Another easy way to fix gaps along the bottom of the baseboard is to replace the small 1/8-round or 1/4-round shoe molding that often covers the bottom of the baseboard. This molding often gets damaged over time anyway, and installing new shoe molding can greatly improve the look of the baseboards. Shoe molding is thin enough that it can be bent to match an uneven floor as you install it.


1:50

Watch Now: How to Install Shoe Molding or Quarter-Round Molding

Before You Begin

Unless you can find a caulk that exactly matches the color of your walls and baseboards, make sure to buy a paintable caulk. Paintable caulks are usually acrylic latex products, and they sometimes have some amount of silicone included in the mixture. Non-paintable caulks, on the other hand, are usually pure silicone products with an oil base. While these can create a very good seal, paint does not stick to oil-based silicone caulk.

While siliconized acrylic latex is slightly more expensive than straight acrylic latex caulk, many people find that it adheres better and creates a longer-lasting joint.

Caulking is not meant to reinforce joints structurally, the way that construction adhesive does. Instead, the purpose of caulk is to seal joints and block gaps through which air and moisture can pass. Because homes are in a constant state of expansion and contraction, you can expect caulked baseboard gaps to open up again over time.

What You'll Need

Equipment / Tools

  • Caulk gun
  • Putty knife
  • Shop vacuum
  • Latex gloves
  • Painter's tape
  • Clean, dry rags
  • Paint brush

Materials

  • Paintable caulk
  • TSP or mild detergent
  • Paint

Instructions

  1. Scrape the Joints

    Successful, longer-lasting caulk beads depend on clean, well-prepared surfaces. If caulking the tops of the baseboards, use a putty knife to scrape away dried paint or drywall compound from the wall and top of the baseboard. If caulking the bottoms, use the putty knife to scrape underneath the baseboards.

  2. Clean the Joints

    Use the shop vacuum to remove the remaining debris, then clean the joints with tri-sodium phosphate (TSP) or a mild detergent mixed with warm water. Let the areas dry thoroughly.

  3. Protect the Floor

    If applying to caulk to the bottoms of the baseboards, run painter's tape along the flooring parallel to the baseboards, about 1/8-inch away. This will protect the flooring from excess caulk.

  4. Apply Caulk

    Mount a tube of paintable caulk in a caulk gun, then run a long, steady bead along the top joint, where the baseboard meets the wall. The bead should normally be no more than about 1/8 to 1/4 inch in diameter.

    Immediately after applying the full bead across the wall, smooth the caulk by dipping your finger in a water bowl and running it along the wet bead. Periodically rinse off your finger to remove excess caulk. Apply enough pressure to force the caulk into the gaps, but avoid the urge to overwork the caulk with your finger. A good caulk bead will have a slightly convex shape in the joint between the baseboard and wall.

    Inspect the caulk bead, and if any gaps remain, apply a small amount of additional caulk and smooth it with a wet finger.

    Repeat the process with the bottom joint, where the baseboard meets the floor. Make sure to force caulk into the joint to fill the gaps. As the caulk begins to set up, carefully remove the painter's tape, which should give you a nice sharp line.

  5. Allow to Dry, and Inspect

    Caulk may shrink slightly as it dries, sometimes creating pinhole-sized gaps. After the caulk has dried, examine it carefully and spot-fix any gaps in the caulk application.

  6. Apply Paint to Match

    Once the caulk dries, paint over the caulk bead to match the existing color. For perfect lines, you may need to paint both the walls and the baseboards with different paints.

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