How to Install Base Floor Trim


Base molding runs along the floor to covers gaps, unfinished wall bottoms and adds a finished look to room. Base floor trim is installed after doorway trim and is usually the last trim installed. The molding consists of either one or two pieces, the base molding itself and sometimes a shoe mold.

Things You'll Need

  • Base and/or shoe mold Cedar shims Tape measure Pencil Miter saw Coping saw Stud finder Finish nails Hammer Nail set Clamp Work table or saw horses Finish nailer - optional Silicone caulk - optional Paintable caulk - optional


  • Sketch the room on paper and show all doorways, inside corners and outside corners. Inside corners need to be coped. Coping a cut is easiest with your dominant hand, so if you are right-handed, plan to cope the right ends of trim pieces at inside corners. Mark on your sketch where you will be coping. These are marked with a "C" in the example sketch. Coping uses a thin saw to undercut a mitered cut so that it fits to another piece perfectly without mitering the second piece.

  • Cut a pair of left and right measuring blocks if you will have to cut for outside corners. Make them about 6 to 8 inches long. These will aid you when measuring for outside corner cuts. Use the base molding you'll be installing so you have the right thickness.

  • Choose an inside corner with a doorway on the right wall. The first piece will not have to be mitered or cut. In the example sketch, this wall is labeled "1" and the next piece is labeled "2." Label your sketch in a similar fashion. If you happen to be left-handed, your numbers should move clockwise, rather than counterclockwise.

Installing the Base Trim

  • Measure the wall from corner to doorway, left to right ("1" on sketch). Measure and cut the first piece on the miter saw, with both ends square cut. Fit into place. It should be a snug fit. If the piece seems slightly long, bend it outwards slightly in the middle to "spring" it into place (recommended).

  • Nail the piece in place. Nails should go into the framing base plate or stud. Use the stud finder to find studs if you have to.

  • Measure the wall for the first coped piece ("2" on sketch). On the miter saw, cut the right end of the piece at a 45-degree angle with the piece standing on its bottom edge. See illustration. The red line is how the piece is to be cut.

  • Lay the board across the work table flat on its back and clamp in place. Cope the miter cut with the coping saw.

  • Measure from the coped edge of the cut back and mark the wall length. Square cut the left end of the piece.

  • Position the piece into place. Ensure the coped corner is tight-fitting. A good cope looks like a perfect mitered joint, but won't open or show gaps like an inside miter will.

  • Work counterclockwise around the room, first cutting the right end of pieces to prepare for coping, then make the coping cut and finally measure and cut the piece to length.

Outside Corners

  • Measure the first outside corner piece. Note that on the sketch that pieces "4" and "5" are out of order. Hold the measure block at the corner (position 5 on sketch) and measure from the corner (position 4 on sketch) to the outside miter edge of the measuring block.

  • Cut the outside miter on the right edge of the piece. Measure back from the cut edge, mark and square cut the piece to the length measured.

  • Position the piece, verify a good fit at the outside corner by matching it up with the measuring block. Nail in place.

  • Cope the right end of a piece for other side of the outside corner. Measure from the inside corner to the outside edge of the piece already installed. Measure from the edge of the cope, mark and cut the left end for an outside corner.

  • Position and nail the piece in place.

Tips & Warnings

  • Coping takes a little practice. Once you do a few pieces, you'll feel like a pro. The keys are to follow the cut line of the inside miter exactly, around the contours of the piece while maintaining a back or undercut of the face of the inside miter. Use a piece of sandpaper to put a razor sharp edge on it and it will fit like a glove. Cut shorter pieces for a tight fit. For longer, coped pieces, make the cut 1/32 or 1/16 of inch long and then bend the piece slightly outward when putting it in place. Then let it "spring" into place. The coped joints will be perfect. Corners, especially inside corners, are never perfect. Sometimes the bottom of the wall doesn't have enough "wall" behind it or the top has too much drywall compound on it. The result is the piece won't sit straight up and down in the corner. Remedy this by inserting pieces of shim behind the piece until it's right. If a gap shows between the trim and wall, fill it with paintable caulk. If a doorway is very close to a corner, you can end up needing a piece of trim an inch or less wide. Don't try to cope these pieces unless there is a doorway on both sides of the corner. In that case, cope cut a longer piece and then cut it to fit. Always cope the longer of the two pieces if possible. Use a dab of silicone caulk behind them to hold them in place. "Measure twice, cut once," goes the old saying and it applies. Double-check your measurements and make sure you've set the saw angle correctly. Sometimes corners aren't 90 degrees. They can be 60 or 45 or any angle from 15 to 120 degrees. All the principles apply, your saw cutting angles just change. Measure the angle and divide by two. For 60 degree corners, your saw cutting angle will be 30 degrees. For angles larger than 90 degrees, take the complement angle which is 180 minus the measured angle. If that is 120 degrees, the complement is 60. Your saw cut angle is then 30 degrees, half of 60. The only difference between installing base molding and shoe molding is the shoe molding is easier. Whether you use quarter round or actual shoe mold, it will go quick and easy and coping your corners takes only a few seconds.
  • Always wear safety glasses or goggles when using power tools, cutting wood or using nail guns. Always wear a dust mask when cutting wood or other materials. Always wear hearing protection when using noisy tools like miter saws. Long pieces of trim can be unwieldy. Support the pieces during cutting with a roller stand or other device.

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  • Photo Credit Photo by Alejandro Forero Cuervo, Illustrations by MJ Logan
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