How to Caulk Baseboards (and Other Ways to Fix Gapped Baseboards)

Caulking Baseboards to Seal the Gaps

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Many homes have baseboards with gaps either at the top or bottom. Gaps are not just unattractive; they can affect your home's capacity for heating or cooling since they can allow drafts to enter your home. One solution is to caulk the baseboards. While caulking the baseboards can help in some instances, it is not a panacea for all gapped baseboards. With the latter, there are several alternatives to caulking.

Why Caulk Your Baseboards?

Applying caulk to baseboards is usually a retroactive measure designed to fill in gaps that occur at the top, against the wall, or at the bottom, adjacent to the flooring.

Top Application

A continuous bead of caulk is applied to the upper ridge of the baseboard, where the baseboard meets the wall. This caulk is usually applied because the baseboard does not hug the wall close enough. Top gaps are more about aesthetics than function since drafts tend to flow from the baseboard-to-flooring junction. Even in newer walls, you may find gentle curves which form gaps along the tops of the baseboards.

Bottom Application

A bead of caulk is applied to the area where the baseboard meets the floor. Over time, as joists sag and foundations recede, gaps develop under the baseboard. In some cases, these gaps are wide enough that they allow air infiltration and can seriously impact your energy consumption. In other cases, these gaps are unattractive or they trap debris.

Pros and Cons of Caulking Baseboards

Pros

  • Inexpensive
  • Easy to do, few skills required
  • Fast to accomplish
  • Easy to paint

Cons

  • Often will develop gaps again
  • Difficult to remove
  • Requires continual maintenance
  • Bottom caulk bead is difficult to paint

Project Metrics

  • Working Time: 15 minutes for a 300 square foot room
  • Total Time: 30 minutes
  • Skill Level: Beginner
  • Materials Cost: $10 to $20

Tools and Supplies You Will Need

  • Paintable caulk
  • Caulking gun
  • Putty knife
  • Shop vacuum
  • Paint matching your walls or your baseboards
  • Plastic, disposable bowl with tap water
  • Latex or substitute gloves
  • Painter's tape
  • Clean, dry rags

Instructions

Smooth the Area

Successful, longer-lasting caulked baseboards depend on clean, well-prepared surfaces. If caulking the tops of the baseboards, use the putty knife to scrape away dried paint or drywall compound. If caulking the bottoms, use the putty knife the scrape underneath the baseboards.

Clean the Area

Use the shop vacuum to remove remaining debris. Clean the areas with tri-sodium phosphate (TSP) or an alternative mixed with warm water. Let the areas dry thoroughly.

Tape the Flooring

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 the excess caulk.

Run the Caulking

After piercing the caulk tube nozzle, run a long, steady bead of caulking along the gap. To smooth the caulk, dip your finger in the water bowl and run your finger along the caulking bead.

Cleaning

Make sure that caulking applied to the tops of the baseboards is smooth, not ridged or bumpy, by smoothing it down again with your finger. After the bottom caulking has cured, remove the tape.

Paint to Match

You can either paint your baseboards a color other than the walls (usually white) or the same color as the walls.

Alternatives to Caulking Baseboards

Houses are continually moving, shifting, expanding, and contracting. Thermal build-up and loss is one reason for this characteristic. Since houses are not solid and static, they have several elements that adapt to movement. The best example is chimney counter-flashing, which allows the vertically moving roof to slide against a stationary chimney, all while keeping the house's interior dry.

So when you connect the wall to the baseboard and the baseboard to the floor, something eventually has to give. Caulk does have some flexibility, but it has its limits. Even if the caulk is expertly applied and well-painted, cracks will form because the baseboard slightly pulls away from the wall.

By caulking baseboards, you set yourself up for a continual cycle of maintaining caulked baseboards: cleaning the area, scraping, re-caulking, and re-painting. This re-caulking cycle will continue for as long as you are in that house.

Because of this, it's often best to explore longer-lasting alternatives to caulking baseboards:

Install Quarter-Round or Shoe Molding

Instead of caulking the bottoms (the floor-to-baseboard junction), nail thin strips of quarter-round or shoe molding. This trim is flexible enough to conform to gaps, even those intermittent sags between joists. This trim comes in wood which can reasonably match the looks of a wood floor when stained. It also comes in medium-density fiberboard (MDF) polystyrene that can be painted.

Replace With More Flexible Baseboards

Thin baseboards can hug the wall tighter, eliminating gaps. If you happen to have thick 9/16-inch (just over a half-inch) baseboards made of wood, look for 7/16-inch baseboards made of polystyrene that hug the wall. You can even use shorter baseboards (such as 2 3/4-inch high) that also conform slightly in a vertical direction to follow waves in the flooring.

Tighten or Re-Install the Baseboards

Sections of baseboard pulling away from the wall can be re-nailed as long as there is a stud behind the drywall. Even tall, thick baseboards can be made to conform to the wall better when nailed down correctly a second time.