Wood or PVC baseboards w/ slab on grade foundation?

A homeowner building a slab-on-grade house asked whether wood or PVC baseboard trim is better where it meets the concrete floor, and whether a small gap under the trim is needed to avoid trapping moisture. The walls in this house were built with rockwool insulation and an Intello membrane (a type of smart vapor barrier that lets walls dry out), then drywall.

Two experienced builders answered on the forum. One said either material works fine, since any moisture at the baseboard will simply pass through the drywall by diffusion rather than getting trapped. He specifically advised against leaving a gap under the trim, noting it would just collect dust, debris, and pests over time. The other builder agreed that moisture isn't a real concern with either material in this setup, but said he personally avoids PVC trim because of environmental and health issues tied to the material, and would choose pine instead.

For a homeowner planning a similar slab-on-grade build, the takeaway is that baseboard choice here comes down to preference rather than moisture risk, as long as the wall assembly itself is designed to dry properly, as this one was. A tight installation without a gap avoids the pest and debris problems that come with leaving space at the floor. Beyond that, it's a matter of weighing wood's traditional look and lower environmental footprint against PVC's moisture resistance and durability.