Installing baseboard.

Finish Carpentry Essentials:

Installing Colonial Baseboard
With Coped Corner Joints

In This Article:

Wide baseboard is installed over a hardwood floor, using scarf joints and cope-cut ends. Problems with the uneven floor and imperfect corners are addressed.

Related Articles:
Skill Level: 3 (Intermediate) Time Taken: A Day Or Two

By , Editor


While remodeling a room in the second floor of my 1960's one-and-a-half story house, I decided to replace the original plain and narrow baseboard with a wider traditional base board.

After finishing the hardwood floor and painting the walls, I was ready to install the baseboard. Remodeled room with no base board trim.


Before Installing Baseboard...

These steps should be complete before base board is nailed to the walls:

  • Walls already painted (preferred, not required).

  • Door casings installed (baseboard butts up against door casing). If using traditional trim, at least the plinth blocks need to be installed.

  • Studs located with stud finder.


Pre-Painting The Trim:

The trim I bought came pre-primed. I gave the trim a light scuff-sanding with 120 grit sandpaper, then I brushed off the dust and applied one coat of semi-gloss interior paint. When the paint was dry, I scraped off any excess paint that had drooled onto the back surface or bottom edge. This excess paint can prevent the trim from sitting tightly against the wall.


5-inch wide MDF baseboard from Home Depot. This is the MDF (medium density fiberboard) base board that I bought at Home Depot.

This classic-style baseboard is about 5-1/4" tall.


Estimating Baseboard Quantity:

It's easy to under-estimate the amount of trim needed for a job. When planning this project, I measured the length of each wall and made a list of the required lengths. I always add a couple of inches to each length, to allow for waste.

One way of estimating materials is to simply add up the lengths of all the walls and buy 5 to 10 per cent extra. But... that method can create problems as the project nears completion and you have a dozen short pieces of trim that need to span the length of a long wall.

I prefer to examine the list of required lengths and find several pieces that can be cut from each "stick" of trim. This works well with MDF trim, which is available in specific lengths, such as 12 or 18 feet.

But solid wood trim is often available in random lengths. Sometimes I'll go to the store with my list of wall lengths, and I will pick out pieces of trim that are a few inches longer than the dimensions on my list, or I will figure out 2 or 3 lengths that can be obtained from one long piece of wood.

My method gives me a load of baseboard where each piece is "dedicated" to one or more walls in the room. Even with my dedicated material, I usually buy one or two extra pieces, because I inevitably make a few mistakes.


I used a stud finder to locate the framing, then I marked each stud location with a piece of blue masking tape.

Previously, I had marked the stud locations on the subfloor, but I forgot to transfer the marks to the walls before I installed the hardwood flooring, so they got covered over. Oops!

Marking wall stud locations with blue masking tape.


First piece of base board laid in position. The first piece of baseboard will be installed like this... but it's not ready yet.


Note how I cut the left end with a 45-degree bevel. This is for the overlapping "scarf joint" that I will use when the next piece is installed. Bevel-cut end of baseboard.


Gap under baseboard near end.

A Problem:

There was a large gap below the baseboard, just a few inches from the right-hand end.

This is caused by a slight upward rise in the subfloor, between the last two floor joists at the side of the house.


To solve this problem, I needed to remove some material from the bottom corner of the baseboard.

I placed a pencil in the floor and slid it sideways across the floor to mark an approximate cut line on the baseboard.

Marking cut line on bottom of baseboard.

Since my pencil line did actually intersect the bottom edge of the baseboard (about 6 inches from the end), I could cut along the line. If the pencil line stayed above the bottom of the board, I could either switch to a skinnier pencil or just cut slightly below the line.


Cutting excess material with jig saw. I cut the bottom corner of the trim with a jig saw.

Note that I applied some masking tape to the base of the jig saw, to avoid scratching the painted baseboard.

Then I sanded the cut smooth.

However, while cutting this MDF baseboard, the jig saw blade chipped the edge of the trim next to the cut. This problem usually doesn't happen when cutting trim made of regular wood. This "tear-out" could be prevented by cutting from the back side, but that requires transferring the cut line, which is not simple unless the line is straight. Tear-out could also be avoided while cutting from the front but using a jig saw blade that cuts on the down-stroke, but using those blades is difficult because the saw jumps around badly.

Sometimes this tear-out problem can be avoided by first making a cut along the line with a sharp knife, then cutting with the jig saw. (I should have done that...)

Once the piece of baseboard was cut to my satisfaction, I fastened it to the wall with a nail gun and 2" finish nails.

I drove 2 nails per stud. I avoided nailing in the contoured part of the trim, because it's easier to fill the nail holes on the flat sections.

Fastening baseboard to wall with finish nail gun.

However, if the top edge of the base won't stay against the wall, I will drive nails through the contoured part.


Installing Carpet?

If the room will be carpeted later, spacers should be placed under the baseboard during installation to create a gap that the carpet can be tucked into. The thickness of the carpet will determine the spacer thickness, but a common spacer thickness I've seen used is 3/8 inch, or just scraps of baseboard (which is often about 3/8" thick).


Connecting Pieces Of Baseboard With A Scarf Joint:

Connecting adjacent boards together with a scarf joint. (Looking straight down)

The best way to join sections of trim along a wall is to employ a scarf joint, where the each piece is cut on a bevel.

I made my bevel cuts at a 45 degree angle, but scarf joints can be made at any angle. Sometimes I use a 30-degree bevel for scarf joint.


Since the floor was uneven, my scarf joint wasn't perfectly tight... it was open at the bottom (red arrow).

I have two options here... I could re-cut the beveled end so the miter angle was just off zero, or I could fill the joint with putty when I fill the nail holes. I chose putty.

Scarf joint on baseboard, with tapered gap caused by uneven floor.


Driving 23 gauge micro-pins through scarf joint. To keep the scarf joint from opening up, I used my micro-pinner to drive short thin nails through the scarf joint.

Some carpenters apply wood glue to these joints, especially when one of the pieces of trim is very short and can't be fastened in many places.


Coped Ends Make The Best Inside Corner Joints:

Test-fitting coped end of baseboard. For the next piece of baseboard, I made a cope-cut on the end.

A coped end has a shape that matches the profile of the board adjacent to that end.

Cutting coped ends only looks difficult. All you need is a miter saw, an inexpensive coping saw, and a few coarse files.

Click Here to read about cutting coped ends.


However... since I had chopped some material from the bottom corner of the first piece, the next piece sat too high. Baseboard sitting too high, profiles don't line up.


Corner joint in baseboard. So I ripped the base board about 1/8" narrower on my table saw. Then I had to file away some material from the bottom to make the trim sit low enough so the tops of the boards lined up.

After I nailed the base to the wall it looked good.


Mitered Inside Corners Are Inferior:

Many do-it-yourselfers may be tempted to simply cut their baseboard at a 45-degree angle and nail it to the wall.

But it just isn't that easy. Look at this example:

Baseboard with miter-cut inside corner joint, showing gap. I nailed these two pieces of baseboard to the wall with 45-degree miter-cut ends.

From several feet away, a gap is clearly visible.


When viewed from above, the gap is even more obvious.

Note how the back surfaces of both of these boards are rounded slightly. Before installing these pieces of trim, I sanded some material off the backs to compensate for the radius of the drywalled inside corner. Otherwise the gap could've been even bigger.

Close-up view of gap between baseboards, mitered corner.

Why does this gap appear?

Very few walls are perfectly smooth, flat and plumb. These walls may lean slightly, which causes the top edges of the baseboard to lean away from each other, causing the gap to form.

With small trim profiles, these gaps may be minor. But with wider trim, especially tall baseboard, gaps on mitered inside corners can get very ugly. It may be tempting to just cover these gaps with caulk, but the corner won't look good and there's a serious chance the gap will open up over time.

The best approach is to use coped cuts on one of the boards at each inside corner.


Why Coped Cuts Make Better Inside Corners:

When looking along the coped piece of trim, the end gap is not visible at all. Base board with coped corner joint, gap is hidden.


Trim with cope-cut corner, gap is visible when viewed from one direction. But when the joint is viewed face-on, the gap is visible.

While any gap can be filled with caulk and painted, trim always looks better when cope cuts are used instead of mitered cuts.

Of course, this leads to another issue... the order of installation needs to be planned before the trim is installed. This is simple, however... you just stand in the room and visualize how the joints will be seen by people walking into the room.

Baseboard installation sequence when using cope-cut inside corners.

The cuts are planned so a person entering the room will be looking along the coped pieces of trim (i.e. the square-cut trim is always placed behind the cope-cut trim, from the viewer's perspective.) This isn't a perfect scheme... sometimes it will be possible to look along the non-coped trim and see the gap.

Click Here to read about cutting coped ends.


Installing Baseboard On Outside Corners:

Next, I turned my attention to the pony wall around the stairwell. There are 3 outside corners here. Pony wall or short-height wall around stairwell.


Short stub wall needing baseboard. This stub wall will require two short pieces of baseboard. I've been saving the small off-cuts for this purpose.


A Problem With Most Drywalled Outside Corners:

Note the gap between the wall and the T-square (red arrow). There is no gap right at the corner.

Most outside corners have a "high spot". The drywall corner bead stands off the wall by about 1/8 inch, so there is a buildup of material near the corner. Consequently the miter cuts on the baseboard will not be exactly 45 degrees.

T-square placed over corner to check out-of-square problems.


First I cut two pieces at a 45-degree miter (using the bevel feature on my miter saw). After a quick test fitting, I realized that the joint was open slightly at the back, so I re-cut both pieces at a slightly greater angle (about 45 degrees, in this case).


Nailing outside corners on baseboard trim. Once I got a tight-fitting corner joint, I carefully positioned both pieces and nailed one piece to the wall. (The right-hand piece still needs to be cut to an exact length at the other end.)


Since my piece of baseboard wasn't long enough to reach the corner, I had to finish the run with a small piece, using a scarf joint. Run of baseboard needed small piece and scarf joint.


Trim With Multiple Complex Cuts:

Short piece of baseboard needing a cope cut and miter cut. When cutting a piece of baseboard such as this small piece on the stub wall, I first made the cope cut and adjusted it until it fit well.

Then I held it in place and marked the back side where it met the end of the stub wall.


Next, I made a 45-degree miter cut on the other end, but I deliberately cut the piece too long. Test-fitting baseboard trim with mitered corner cuts.

It's easy to cut the trim shorter, but I have yet to invent a board stretcher to fix wood that is cut too short. I sometimes cut a fussy piece of trim 3 or 4 times, each time getting slightly closer to the required length, before arriving at the perfect dimensions.

Short pieces of trim on stub wall. After making a few cuts, these two pieces were the proper length.


I decided to make a "return" on the left end of this piece. I made another miter cut on that left end. Short lengths of baseboard with return trim.


"Return" piece of baseboard trim is very short. I cut a small return piece from a scrap of baseboard.

I glued this tiny piece to the left end of the board mentioned above, and I secured it with some 1/2" micro-pins.


When the glue was dry on the return, I glued the front piece to the side piece and fastened them with micro-pins.

When I'm installing small pieces of trim, I often glue and nail them together first. Once the glue dries (in about an hour) I can use a belt sander to grind down the back surfaces to make the assembly fit perfectly.

Several short pieces of trim glued and nailed together before installation.


Baseboard on short stub wall. Then I nailed the assembly to the wall with 2" finish nails.

Unfortunately the mitered gap opened up, because it should've been mitered at an angle greater than 45 degrees. Later I can fill this gap with putty.


Carry On...

Then I went back to the outside corner where I started installing baseboard.

I cut the right-hand end of this piece of base until it matched the mitered end of the loose piece around the corner (arrow).

These miter cuts were about 46 degrees.

Installing base board trim on short wall with slight curve.


Mitered corner on baseboard showing protruding wood. I encountered this hassle... the lower part of the next piece of baseboard was sticking out.

This was caused by two problems: First, the previous piece of trim was just a tiny bit too short. As I nailed the trim to the wall it conformed to the curved contour of the wall and drew away from the corner by about 1/32". Since that short wall has drywall corner beads at each end, both ends of the wall protrude outward slightly, which makes the entire wall appear curved.

The second problem was that the wall behind this next piece of trim had some buildup of drywall mud near the corner, and this made the wall bulge out just above the floor.

Did I mention that there can be a ton of problems when doing trim? This is especially true when trying to make the woodwork look flawless. Maybe I'm too much of a perfectionist.

So I marked the next piece of baseboard on the back side, at the bottom (red arrow). I used a belt sander to grind away this excess material. Back side of trim with area marked for sanding away.


Outside corner after trim corrected. After grinding away some material from the back, I installed the baseboard. It fit well and was standing straight up, not leaning at an angle.


Make It Fit Tight:

When installing a piece of baseboard that is long enough to span between two corners, I normally cut the trim just slightly longer than necessary, perhaps 1/16" or less.

I place one end of the board in a corner. Then I flex the board so it bows outward slightly, and force the other end into its corner.

By pushing the middle of the board against the wall, the ends will be pushed tightly into the corners. Then I fasten the baseboard at the middle and work towards the ends.

Baseboard in alcove, both ends are cut square.

Both ends of this piece of baseboard
are square-cut.


A Tip For Tight-Fitting Square-Cut Baseboard Ends:

Square-cut end of baseboard can't sit tight against corner. When installing baseboard with square-cut ends, the back corner often won't sit tight against the wall because there is a slight radius to drywalled inside corners.


To make the baseboard sit tight against the wall, I grind a small radius on the back edge of the baseboard with a rasp or file. Using a file to make a slight radius on back corner of baseboard.


Touch-Up After Installing Trim:

After the baseboard installation was complete, I applied wood putty to all the nail holes and the gaps at the outside corners. Filling nail holes with wood putty.


Caulking gap at top of baseboard. I caulked the larger gaps along the top of the baseboard, and also the gaps at the coped inside corners.


After the putty and caulking was done, I applied masking tape where necessary and painted the trim again. This gave the trim a clean, seamless appearance.

Read more about touching up pre-painted trim after installation.

Touching up paint on baseboard.


The Finished Baseboard Project:

Remodeled room with new baseboard. The original trim in the upstairs of this 1960's house was plain, boring "modern baseboard".
I much prefer the subtle details of this 5 inch traditional baseboard. Pony wall in remodeled room, with new colonial baseboard.


An Extra Step:

Gap between traditional baseboard and wood flooring. When installing baseboard in a room with hardwood flooring, it's common to have gaps below the base caused by waviness in the flooring.


Sometimes I will install a shoe moulding at the bottom of the baseboard. I always nail the shoe moulding to the baseboard, not the floor.

I normally just miter-cut the inside corners on shoe molding (instead of cutting coped ends), because it's easier and adjusting the cut to fix small gaps is no big deal.

Installing shoe molding to baseboard, to conceal gaps.


Notes About Installing Stained Trim:

Whenever I do a stain-grade trim job, I apply the stain and urethane before cutting and installing the trim. The installation of stained trim is similar to the project shown here, with the following exceptions:

  • After the trim is installed, there is no more finishing required except for touching up the nail holes and some cut ends.

  • Depending on the color of the wood, nail holes might need to be filled with a color-matched wax crayon (Minwax sells these, for example). Sometimes all that is needed is to apply a felt-tipped stain marker (Minwax sells these too) to the nail holes and cut ends so the unstained wood fibers get colored. I've found this necessary for dark-stained wood.

  • There is usually no need to fill any gaps at the corners or along the tops of baseboards.


More Info:

Tools Used:
  • Basic Carpentry Tools
  • Miter Saw
  • Finish Nail Gun and Air Compressor
  • Jig Saw
  • Coping Saw
  • Files: Round, Triangle, Flat
  • Belt Sander
  • Micro-Pinner (Optional)
Materials Used:
  • Baseboard, Colonial, 5"
  • Finish Nails, 2 Inch, 16 Gauge
  • Masking Tape
  • Carpenter's Glue
Related Articles:



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Written November 18, 2009