Wet Ground
Watch out for soil that is wet or if there are puddles in the crawlspace. Also look for discoloration of the concrete block wall to see if in the past there was significant moisture in that area.
Falling insulation
Air moisture in the crawlspace can soak the insulation up against the subfloor and cause it to fall. and if it remains against the subfloor while wet, there is higher risk of wood rot.
High Humidity Levels
Humidity in the crawlspace is safest around about 55% or lower.
Cheap Moisture Barrier
Homes with cheap plastic moisture barriers don't seal off the moisture effectively, and if the AC is in the crawlspace, the ducts can sweat and leave puddles of water on top of the liner as well.
Soil Washout
Look for signs of water washing out soil, leaving a puddle shaped indent in the soil.
