My wife and I are building a house, and our builder is telling us that the hardwood should be installed against the baseboard rather than underneath it. I have always believed the opposite to be true, and wanted to hear from people who would know. I am not sure if I should insist that the hardwood go underneath...

Baseboards are typically installed after the wood flooring. However, if the baseboards are quite tall and ornate, have them installed first, then the floor, then have baseshoe molding installed at the junction of the floor and the baseboards. This is the traditional way of doing it.

The baseboards should be held up off the floor if they are installed first. This will create a gap for the expansion of the hard wood. If they are held up 1" for a 3/4" solid install, your baseshoe will cover this gap no problem.