Strange smell coming from gaping holes in bathroom vanity

Question

Every now and then I'll notice a sort of damp smell in the bathroom. It seems to be coming from inside the vanity, under the sink, where there are some gaping holes around the plumbing.

1. I am of course concerned about mold. How can I go about checking for mold with the least amount of demolition? I once called a mold company for something else and they basically told me that they can't test for mold unless they can physically access the area in question.
2. Easiest way to patch up these holes that looks decent? For the drywall, I'm thinking I'll just use some mesh and spackle. But the hole is pretty big so I'm worried that the slightest push will cause it to cave in. Maybe some spray foam first to give it some support? For the bottom of the vanity, which looks like particle board, I don't know what to do.

Answer 1

• To see inside the wall with no demolition, you might try an endoscope, such as those shown in this search on Amazon. That would not provide as complete a view as taking down the wall and cabinet, but might allay fear of fungus.

• The pipe through the wallboard is likely attached to a stud, which also supports the wallboard. You could square the hole and cut a patch, but just putting a backing strip or two in place to hold spackling should be sufficient. You might add an escutcheon plate (collar or flange), such as this from Amazon. A larger one could cover the hole completely, sans spackle.

• For the slots in the bottom of the cabinet, you might cut some closed-cell polyethylene foam strips (often used in packaging) to make a moderately tight fit. Though pressure alone should hold them in place, a dab of construction adhesive could be added.

N.B.: Links are only for illustration, likely other products would do as well or better.