How to Fit Baseboards With Mitered Inside Corners

Fitting baseboards with mitered inside corners can transform the look of a room, giving it a polished and finished appearance. While it requires some careful measuring and cutting, installing baseboards with clean 45-degree mitered corners is an attainable DIY project for most homeowners. Here is a step-by-step guide on how to fit baseboards with mitered inside corners.

What You’ll Need

Baseboard material – wood, MDF, vinyl, etc.
Miter saw – preferably with a miter guide for precision cutting
Miter box with backsaw – for making manual 45-degree angle cuts
Tape measure
Pencil
Coping saw – for coping trim at inside corners
Wood filler/putty
Brad nailer/nail gun
Hammer
Finishing nails
Wood glue
Sandpaper
Paint/stain and supplies

Preparing the Walls

Before installing the baseboard, make sure the walls are prepped properly:

Fill any holes or imperfections with drywall spackle. Sand smooth when dry.
Apply primer to raw drywall or patched areas.
Paint the walls in your trim color so the baseboard blends in seamlessly.
Ensure the flooring is installed and complete.
Vacuum and wipe down the base of the walls to remove dust and debris.

Measuring and Cutting Baseboard Pieces

Proper measuring and cutting are crucial to getting clean 45-degree mitered inside corners. Here are the steps:

Measure the length of each wall and cut baseboard pieces roughly 6 inches longer, to allow room for error.
Place the baseboard piece against the wall, lined up to where you want it installed. Mark the back side at the two end points.
Take the baseboard to your miter saw. Line up the marks with the saw blade to get 45-degree angle end cuts. The two angled ends should meet precisely at a 90-degree corner.
Use a miter guide, if possible, to ensure the 45-degree angle is exact. Cut slowly and smoothly.
Test the fit of the two mitered ends at the corner. If there is a gap, adjust the angles slightly and re-cut until you achieve a tight seam.

Coping Inside Corners

For the most professional look, use a coping saw to shape the inside corners:

On the uncut end of one mitered baseboard piece, mark 1/2-inch in from the end and trace the profile.
Clamp the baseboard piece firmly. Use a coping saw to cut along the traced line.
Test the coped end on the mating baseboard piece. It should fit snugly into the corner.
Sand or file the edges of the cope so the join is seamless.
Repeat the coping steps for the other corner piece.

Installing the Baseboard

Once your pieces are cut and coped, you’re ready for installation:

Run a bead of wood glue on the back side of each baseboard piece.
Position the piece firmly against the wall and nail into place by hand or with a brad nailer. Use finishing nails if nailing by hand.
Place nails every 12-16 inches, angling slightly toward the wall. Set nails and fill holes.
For mitered corner joints, apply wood glue to both mitered ends. Tap together gently with a rubber mallet.
Use painter’s tape to hold joints snug until the glue sets. Remove tape after about 30 minutes.
Continue installing pieces, checking mitered edges for tight fit. Adjust and re-cut as needed.
Once all baseboard pieces are installed, caulk corner joints and nail holes. Allow to dry fully before painting.

Painting the Baseboards

For a cohesive look:

Lightly sand installed baseboards to scuff the surface for paint adhesion.
Carefully apply primer and 2 coats of paint in your trim color. Allow proper dry time between coats.
Use a small brush to carefully paint the inner edge of mitered corners.
Remove any painter’s tape and touch up paint as needed.

Fitting baseboards with polished 45-degree inside mitered corners takes careful measuring, cutting, and some finesse coping the joints. But the end result is well worth the effort for beautiful, seamless corners that catch the eye. Take it slow, double check angles, use glue and nails for strength, and paint for a flawless finish.

Frequently Asked Questions About Fitting Baseboards with Mitered Inside Corners

How do I get a tight mitered corner?

Take time to precisely measure and cut perfect 45-degree angles. Use a miter saw guide if possible. Test fit the joints and recut as needed until the mitered edges join up flush with no gaps.

How do I hide imperfect mitered corners?

Minor gaps can be filled with wood putty before painting for an invisible fix. For more noticeable gaps, apply wood glue and draw the joints tightly together with painter’s tape until the glue dries.

Should I nail or glue when installing baseboards?

Use both. Apply wood glue to the back and mitered ends before installing, then nail the pieces in place. The glue provides strength while the nails hold everything tight as the glue dries.

What’s the best way to cope inside corners?

Mark 1/2-inch in from the end of the baseboard and trace the profile. Use a coping saw to carefully cut along the traced line. Test fit on the mating piece and sand or file as needed for a perfect join.

Should I install or paint baseboards first?

It’s best to install baseboards first, before painting walls. Paint the trimmed-out walls right up to the baseboard edge. Then caulk and paint the baseboards in the same finish as the walls for a seamless look.

How do I get paint out of mitered corners?

Use a small paintbrush to carefully apply paint into the interior V of mitered corners. Avoid over-brushing or applying too much pressure which can pull paint out of the joint.

Can I use pre-primed baseboards?

Yes, pre-primed MDF baseboards can save time on prep. But you’ll still need to lightly sand and apply at least one coat of paint for a uniform finished look that matches the walls.

How do I finish mitered corners without nail holes showing?

Set finishing nail heads below the wood surface with a nail punch. Fill holes with wood filler, matching the color as closely as possible to the base color.

Fitting baseboards with mitered inside corners results in clean, sharp lines and a polished, upscale look. With careful measuring, cutting, and nailing techniques, as well as a quality paint job, you can achieve beautiful, seamless trim work like a pro. The added effort is well worth it for baseboards that become a focal point in your rooms.

Conclusion

Installing baseboards with mitered inside corners not only finishes off a room beautifully, it also demonstrates your carpentry skills and eye for detail. While it does take precision cutting and finesse to achieve tight joints, the visual impact is significant. Miters transform simple baseboard trim into an elegant design statement. By following the techniques for accurate measuring, cutting perfect angles, coping the ends, gluing, and nailing securely, you can create flawless corners that look professionally installed. Take your time, repeatedly test fit the joints, and don’t be afraid to re-cut pieces for the cleanest possible finish. The difference between snugly fitted versus gapped miter joints is obvious. With some patience and practice, you can master the art of installing baseboards with seamless mitered inside corners that you’ll appreciate every time you enter the room.