Join Baseboards With The Scarf Joint For a Solid Connection

Scarf Joint
Scarf Joint. © Lee Wallender

When you shop at your home improvement store for baseboards, you’ll notice that they come in extremely long lengths:  16 feet long and even more.  The best case scenario is to run a single, unbroken length of baseboard on each wall.

In most cases, this is not possible.  When the wall is longer than the baseboard, you need to splice two shorter baseboards together to stretch from end to end.

No Butts About It!  

A butt joint—the worst kind of joint for baseboards--is where you cut the ends of the two pieces at 90-degree angles and splice them together.

The problem is, you cannot really join the two pieces together well.  Nails get driven into the baseboards at weird angles and don't stay firmly in place.  Eventually, the baseboards separate.

A much better technique is the scarf joint. 

Scarf Joints For Baseboards

Tools

  • Saw:  For a clean, precise scarf joint, use a miter box and hand saw, but preferably an electric miter saw.  Invisible scarf joints depend on precise 45-degree angle cuts.  
  • Nailer:  For nailing, an air compressor-driven or electric nail gun is far preferable to hand nailing with a hammer and finish nails.  The reason is because hand nailing light-weight wood such as trim causes it to rattle and move out of position.  The fast, decisive strike of the electric fixes the baseboard in place before it can shake out of position.
  • Nailset:  If you plan to nail by hand, a nail set will help you drive the head of the finish nail flush with the surface without damaging the surface.

    Technique

    1. Cut First Board:  Cut the end of one baseboard at a 45-degree angle with the bevel facing the room.
    2. Cut Second Board:  The other baseboard is cut also at a 45-degree angle, but with the bevel facing the wall.
    3. Dry Fitting:  Experiment to make sure the two pieces fit together. If the baseboards are too long, you may have to shave off a bit with the miter saw.
    1. Wood Glue:  When they are the right length, run a thin bead of wood glue along one of the bevels.
    2. Nail:  Mate them up and drive 2 nails so that the two baseboards are joined.

    The image here shows the two boards slightly separated for effect so that you can see the difference between them. 

    Advantages

    • Firmer Joint:  Scarf joints, if nailed properly, will not come loose.  
    • Smaller Seam:  Because one baseboard lays on top of the other baseboard, the seam is far smaller than with butt joints.
    • Easier Nailing:  Allows you to drive the finish nails straight into the board (90-degree angle) rather than at other angles that are more difficult to achieve with manual hammering. Because the scarf joint angle runs at 45 degrees, your perpendicular nail will run through that area.