We have been noticing an intermittent bad smell coming from a cupboard in our kitchen and our bathroom. This has been going on for a couple of months, and it seems to come and go, sometimes lasting for a few hours, sometimes a few days, and then not showing up again for another few hours/days.
Today we had a plumber out to look at it as we thought it might be something to do with the plumbing. I don't know much about it, but he seemed quite thorough. His opinion was the the plumbing itself looked fine, and he felt that the problem might be damp under the floors as he pinpointed the source of the bad smells to two holes, one in a kitchen cupboard and one behind the bath, both of which go under the concrete flooring.
He wasn't able to get access to the underfloor area. We have underfloor heating, and the ground floor is underlain by solid concrete. He did note that there didn't seem to be an access hatch, or venting bricks, and that the foundations for the house were slightly under the ground surface level. He also spotted a small patch of crumbling brick/plaster at the very base of the house on one corner which is next to the hall (exterior).
He said at this point he couldn't do anything further, and that we had three courses of action. As I have no knowledge on these things I would like some advice, if possible, on the costs, and any problems with choosing any of these options.
1) do nothing. The smell isn't very strong, is intermittent, and can be got around by opening a window for a few hours.
2) turn the underfloor heating on. The problem started when the weather got warm enough for us to have the heating off all the time. Putting the heating on once a day for a couple of hours may keep any damp problems at bay.
3) Get a builder in to investigate further. This would at least involved cutting an access panel, and then possibly damp remediation works depending on what is found under the floor.
We don't want to leave a problem that will get worse, and might potentially damage the house, but at the same time we are probably going to be moving house within the next two years, and don't want to spend thousands of pounds which we almost certainly won't get back.