How to Seal Gaps Under a Baseboard

Measuring and Marking

• 1

  Measure from corner to corner of your baseboard moulding, along its bottom edge, using a tape measure.

• 2

  Use the tape measure to measure along the top edge of the moulding and mark a distance equivalent to the length of the baseboard using a pencil.

• 3

  Position the moulding on the miter saw, with the bottom on the saw table and the back of the moulding against the saw's fence. Set the angle of the saw for the angle of the corner, a standard 90-degree angle requires two 45-degree angles, one on each of the two pieces that make up the corner.

Cutting and Installing

• 4

  Align the blade with the mark on the moulding. Position the blade to the left of the mark for a left end cut and to the right for a right end cut. Angle the cut into the face of the moulding for an inside corner, so that the bottom edge is shortest, and away for an outside corner, so that the bottom edge is longest.

• 5

  Hold the moulding firmly against the table and fence. Start the saw and make the cut in one fluid motion. Allow the saw blade to stop before allowing it to spring back up to prevent chipping.

• 6

  Fit the moulding piece against the wall so that the mitered ends align to the ends of the wall. Place the moulding firmly on the floor and the back of the moulding against the baseboard to cover the gap. Nail the moulding in place with a pin nail gun and 1 1/2 inch pin nails, one nail every 8 inches.