Agreed. It will look nicer if you caulk any gaps for a nice airtight look. Make sure you use a paintable caulk. You can have a bit of silicone in it but pure silicone is the work of the devil and you will not be able to paint over it.
Actually - there isn't a "need, but backpriming ( that's what it's called)can help keep the wood stable and less shrinkage.
In some exterior situations it can give years to a paint job, but that is a different story..
"It's better to come here with questions before you screw up than to come here after and ask how to fix them."- JS
The Following User Says Thank You to Brushjockey For This Useful Post: