No matter how meticulously you measure your baseboard joints, there are bound to be gaps in the joints. If left like this, your DIY baseboard job is bound to look like a home job.
Above is a rounded 45 degree corner joint. It’s a tough one. Caulk is the obvious answer to filling the joints, but before you jump to the caulk, sanding down the transition edges will give you a finished product with an almost invisible joint.
Might I suggest using a set of hand files, instead of regular sand paper.
#1 – It’s easier, and
#2 – It comes out looking much more professional.
After using the files we a have nice smooth transition, no wavy bumps, and very minimal gaps:
Now go ahead and caulk your baseboards!