Upgrading half-wall basement insulation

Q: How can I deal with the partially insulated basement walls in my new home? A layer of insulation extends partway down the wall, with no frame underneath. Should I rip it all off and start from scratch? What about building a new insulated wall and leaving the old insulation in place?

A: The decision you’re facing is quite common and it springs from the fact that building codes don't always require basement wall insulation to go from floor to ceiling. Some higher-end homes have full-height insulation, but many houses don't. And as you'd guess, there are a few ways to handle the challenge. First, and most importantly, your basement must be completely dry before you continue. And don't let wishful thinking get the better of you here. Bone-dry or don't finish at all. Since typical code-minimum walls don't have any sort of framing present (usually just a blanket of floppy, foil-backed fiberglass), you must either build a frame, or strip the existing insulation off, throw it away and use a system of rigid foam and wood strapping to support your wall board. My preference here is to remove or slit the vapour barrier on the existing insulation, build a new stud wall, then insulate it and install a new vapour barrier on the warm, inner surface. Insulating with foam sheets is my choice for bare-wall basements, but since you've already got some insulation in place, you might as well use it.