Every home does have mold. Mold is a spore that floats in the breeze. Naturally occurring wherever the climate is right for that specific mold. Mold is one of natures most simplistic and persistent occurrences. It was here before us, and will persist probably beyond the cockroaches.
What makes mold? Moisture and substrate to feed. Also known as; Moist drywall.
What types of mold are there and are they dangerous? You're not a mold expert, don't pretend to be. Mold experts have a variety of testing and identification tools. But just rule of thumb; If it's black and blue, I think that's where you get concerned. Or was it green and yellow? HA! You need to rely on mold experts.
If you see black mold, you should vacate and put a mask on. If you see fluffy mold going all 3 dimensional off of the surface, you should vacate and put a mask on. I keep one of those cheapie rubber masks with the orange mold and lead dust face filters. The little replacement pads are about 5 bucks each, or 10 per set. Unless you get actual exposure, the pads stay good for quite some time.
OP: "They've got sump pumps so it's no longer a concern." Oh contrair dear bear, that's not true. Now they have a brand new concern which is routine maintenance of sump pumps for viability and proper operational effect. It's just one of those standard recommendations if a home relies on a sump pump. Pumps needs periodical checking because it's probably just a cheapie off the shelf pump with mechanical parts that are not everlasting. And do they have backup generator power? How quick does the water rise? How frequent do the pumps run? Those are rare a-typical considerations but still keep your eye out.
I had a home once that ran water upward and outward, and after a week of no power, the sump pit was bubbling up and down with water. But water table issues are seasonal and cyclical. In CO, water tables and actual need for sump pumps can vary on a 10 year cycle or longer. There was this news article of how the builder had no idea the water table would get this high, and residents were pumping to the neighbor, who was pumping to the next neighbor. Everyone had a river coming out of their basement and they were just fighting to get water out, with nowhere for it to go. People were using backhoes to dig ditches to try and get it out of that general plains areas. Next year, tables went down, and it's no big deal until the next cyclical run through.
Proper mold remediation involves spraying, chemicals, air drying, material removal, and what not. Once mold is present, it is forever persistent within materials. The chemicals kill a lot of spores but you can't kill all microbial presence. It's true every home has mold. But it's also true that mold typically cannot persist in a dry environment. It goes dormant and dies back to a microbial point like a mini mustard seed.
Valuation method? I've dealt with that many times, and only a few times for very severe conditions, and I think it was easier to valuate because the problem was ongoing requiring repair. I got all sick from entering without a mask, so that's when I looked into the problem into detail. It's probably more difficult to state stigma and what not.
The general industry opinion, as I personally understand it (Consult A Mold Expert First!), is that once mold and moisture are remediated, materials swapped, and coverings applied, the mold is contained. Think of mold hazard as a temporary condition, only applicable when it's alive. Major repair costs, and remediation solution costs and efforts are necessary. Once you've got a handle on moisture and remediation though, it's supposedly dormant and you don't have to worry about it. But you'd better make dang sure your sump pumps work well, so you don't light that mold back up with some moisture condition.
I've seen mold from everything from a forever open window, to dog pee walls in basement, to area flooding, to poor gutter management which seeps into walls. You'll cop moisture issues from drainage, positive water flow, busted pipes, lack of sump pits and pumps, and whatever you can think of. It can be in the attic, the basement, behind walls, you name it. That's why water delivery systems and gutter drain systems are important. Also you probably won't see mold very often. And it's not like go crazy with fear when you see it. It's typically only a major issue in single family detached, when major neglect occurs.
Valuation methods I'd say; rely on the mold experts opinion with specific points regarding itemized remediation methods and an accompanying statement of habitability and safety. For valuation methods, if it's remediated, it's probably not a stigmatized issue. You'll run into stigmatized issues more with attached units where remediation is more difficult. I'm not the expert, but I have struggled with moldy disasters in the past. I've got a picture of a hot tub in a living room somewhere in my work files. Mold everywhere. I'll see if I can think of which file that was and perhaps post a pic later. Was 7years ago though or something.... You're not the mold expert. You must rely on mold experts. It's that simple. Scope of work would include being privy to every single document regarding remediation efforts and costs and habitability statement. Scan it in, assume, disclose, and valuate as normal if it's properly remediated. Pass the buck to the mold inspector. He's the expert on the matter. You just valuate based on assumptions and supplied information.
