How to Install Baseboards

Baseboards are the detail work that makes a room feel finished. They hide the transition between wall and floor, conceal gaps from uneven subfloors, and protect drywall from kicks and vacuum cleaners. A well-installed baseboard sits tight against both the wall and floor with clean, tight joints at corners—it's noticeable when done right and invisible when done well. This is a project you can tackle in a day across most rooms, and it requires only basic tools and patience with your miter saw.

1. Map Before You Cut. Walk the perimeter of your room with a tape measure and note every wall length. Mark where corners fall and where you'll need to splice pieces end-to-end. Sketch a simple diagram showing wall lengths and corner types (inside corners, outside corners, door openings). This prevents buying too little material and tells you exactly how many cuts you need to make.
2. Clean Surfaces Hold Better. Vacuum and wipe the base of every wall where baseboard will land. If you're installing over new subfloor, make sure all flooring is fully installed and settled. Check for gaps between wall and floor using a straightedge; baseboards will telegraph any humps or dips. Fill large gaps with a backer rod before installation—it makes the caulk job cleaner and faster.
3. Straight Cuts Come First. Set up your miter saw and cut the first wall straight across both ends (90-degree cuts). Mark the back of each piece with the wall it belongs to—it saves confusion. Start with straight runs between corners; you'll handle corners after all straight pieces are on the wall. Dry-fit the piece against the wall to check for gaps before you secure it.
4. Adhesive Plus Nails Wins. Apply a bead of construction adhesive to the back of the baseboard, spacing beads 12 inches apart. Press the piece firmly into place, checking that it sits tight against both wall and floor. Drive 2-inch finish nails through the baseboard into the wall studs, spacing them 16 inches apart. Set the nail heads slightly below the surface with a nail set—you'll fill these later.
5. Cope Inside Corners. Cut the first piece to meet the corner at 90 degrees. Then cut the adjoining piece at a 45-degree angle into the corner (called a coped cut), so it overlaps the first piece and follows the profile of the baseboard. Test-fit the coped piece; it should sit flush against the baseboard and wall with no gaps. Apply adhesive and nail it in place the same way as straight sections.
6. Miter Outside Corners. For outside corners (where two walls meet on the exterior), cut both pieces at 45-degree angles so they meet point-to-point at the corner. Dry-fit both pieces to ensure a tight joint with no gaps. Apply adhesive to both pieces, press them together at the corner, and nail them in place. If the joint gaps slightly, it will close when you caulk.
7. Seal Every Gap. Load a caulking gun with paintable caulk and run a bead along the top edge of the baseboard where it meets the wall. Smooth the caulk with a wet finger or caulk tool, pushing it into the gap. Then fill all nail holes with paintable wood filler, overfill slightly, and sand smooth once dry. Caulk any remaining gaps between baseboard and floor.
8. Paint Hides All Sins. Sand all filled nail holes and caulked areas lightly with 120-grit sandpaper to feather them smooth. Wipe away dust with a tack cloth. Apply primer to any raw wood or filled areas, then paint the baseboard to match your trim color. Two coats of paint typically covers best and hides filler and caulk.