Our house is 1963 ranch built on slab, clay soil coastal CA. Tented in 2017 and then spot treated for termites 2022, attic was sanitized sealed and re-insulated in 2018. All windows and entire roof replaced in 2017. Stucco exterior and I don’t think there is a sill or anything in the foundation (probably just framing bolted to concrete slab…) there is a very generous roof overhang on all sides, which helps keep rain off the walls and around the foundation (but our lot is very level and soil does not drain well, we have had a couple wet winters and the soil around the foundation is definitely saturated during winter).

We’ve been noticing weird unpleasant smells when the house is closed up even overnight increasingly over the past few years. Not exactly musty or moldy, or distinctly damp or rotting - just not good. Maybe a bit sickly sweet? And the strongest smelling room is our master bedroom. I’m concerned there could be damp or rot in the walls coming up from cracks in the foundation or up between the slab and walls.

What kind of professional should we be seeking to investigate the cause? What methods might we use ourselves to narrow things down?