Installing Baseboards at the Floor Line

Baseboards are the transition between floor and wall—they hide the gap where flooring naturally settles, protect the wall from vacuum damage and foot traffic, and frame the room visually. Done well, they look like they belong there, sitting flush and level, with seamless joints at corners. Done poorly, they gap at the floor, twist away from the wall, or have visible nail holes and gaps at corners. The install itself is straightforward if you follow the sequence: measure the room, cut your pieces to length, handle the corners properly, and fasten everything with nails driven into wall studs. Most rooms take a day, and the result holds for decades.

1. Map Room Dimensions. Walk the room with a tape measure and note the length of each wall. Sketch it out on paper. Mark where you'll need inside corners (concave), outside corners (convex), and any transitions to other rooms. Count your linear feet and add 10% for waste. Baseboards are often sold in 8- or 10-foot lengths, so calculate how many pieces you need. Plan your corner strategy now: you'll either miter (45-degree angle cuts on both pieces) or cope (scribe one piece to fit the profile of the other). Coping is more forgiving and hides movement better, but mitering is cleaner if done precisely.
2. Clean the Wall Base. The wall should be clean, dry, and free of dust, paint flakes, and debris. Vacuum or wipe the base of the wall where the baseboard will sit. If the flooring is new and slightly proud (raised) where it meets the wall, you may need to scribe the baseboard to fit—this means cutting the bottom edge to match the uneven floor. For most installations on level floors, this step is just a cleaning pass.
3. Cut Straight Baseline. Start with the longest straightaway wall. Measure the exact distance from corner to corner. Cut your first baseboard to length using a miter saw. Cut square (90 degrees), not at an angle. If the wall is longer than a single board, you'll butt-join additional pieces in the middle of the wall, away from corners. Set this board in place and check that it sits flat on the floor and tight to the wall along its full length. Make small adjustments if needed.
4. Cope Inside Angles. An inside corner is where two walls form a concave 90-degree angle—like the corner of your living room. The coping method: cut the first board square to length and butt it into the corner. On the second board, mark where it meets the first piece. Use a coping saw to cut along the profile of the first baseboard's face, creating a scribed edge that wraps around it. The straight back of the second board still goes against the wall, and the scribed front fits over the profile of the first. This hides gaps that open and close as the house settles.
5. Miter Outside Joints. An outside corner is where two walls form a convex 90-degree angle—like a corner that juts into the room. Measure to the outside corner point on both walls. On a miter saw, cut both pieces at 45 degrees, with the cuts facing inward so the outside corner appears seamless when joined. The two pieces meet point-to-point at the corner. Test-fit first: the joint should be tight with no visible gap. If one side opens slightly, adjust your saw angle by a quarter degree and recut.
6. Fasten First Section. Position your first prepared board in place. It should sit flush on the floor with no gaps and sit tight to the wall. Use a finish nailer or hand-nail with 2.5-inch finish nails, driving nails through the baseboard into the wall studs behind it. Studs are typically 16 inches apart. Find them with a stud finder or knock along the wall for a solid sound. Drive nails at a slight downward angle so they pull the baseboard down and back. Space nails 16 inches apart, with at least one nail per stud. Sink nail heads just below the surface.
7. Lock Coped Corners. Set your coped baseboard in place at the inside corner. The scribed edge should nestle against the profile of the installed board. Check the fit—gaps mean your cope needs adjustment. Once satisfied, nail this board in place using the same stud-finding and nailing method. Drive the first nail near the coped end to lock it in, then work along the length.
8. Secure Mitered Joints. Bring both prepared boards to the outside corner and test the miter fit. Once confirmed, nail one side fully in place first. Then position the second board so its mitered edge meets the first piece. The joint should close with no visible gaps. Nail the second board in place. The outside corner itself typically won't have nails—you're nailing the straight sections of each board into the wall studs.
9. Complete Room Perimeter. Continue around the room wall by wall, cutting each board to length, test-fitting, and nailing. For long walls requiring multiple pieces, butt-join them in the middle of the wall by cutting both ends square and pushing them tightly together, then nail both pieces into studs. Work your way around the room in a logical sequence—typically along one long wall, across the short wall, along the opposite long wall, and finally the remaining short wall.
10. Seal All Gaps. Once all boards are nailed, fill nail holes with paintable caulk or wood filler. Apply caulk with a caulk gun, overfilling slightly and smoothing it flush with a wet finger or caulk tool. For gaps between baseboard and wall or floor, use paintable caulk—it allows for slight seasonal movement while remaining invisible. Apply caulk in a continuous line and smooth it. Let everything cure per the product instructions, typically 1-2 hours for quick-dry options.
11. Smooth Surface. Once caulk is dry, sand any rough spots or high edges lightly with 120-grit sandpaper. Sand the cured filler flush if needed. Wipe away all dust with a tack cloth or damp rag. The baseboard surface should be smooth and ready for primer and paint. If the baseboards come pre-finished, you may skip this and just touch up nail holes. If you're painting, prime the filled nail holes and any raw wood exposed by cuts.
12. Finish with Primer and Paint. Apply one coat of primer to the entire baseboard run, including all joints and filled nail holes. Let dry per the primer instructions. Then apply two coats of finish paint, allowing drying time between coats. Use a quality brush or small roller. Paint along the top edge where the baseboard meets the wall, along the front face, and along the floor edge. Paint into all coped and mitered joints so no raw wood shows.