I’ve read that mere gravity can force the water in the ground through building foundations and thereby provide the moisture needed for mold to develop. Well, it just so happens that in a friend’s building, a wall that developed a good deal of mold is the wall right next to where an old torn-off roof was thrown. It laid there for about two days before it was hauled away. It had to have weighed between 5 and 8 tons. The mold was noticed about 3 or 4 days after the roof was removed.
Is it possible that the weight of the roof was transferred to the water in the ground, and that forced water in?
Well, if you compress soil, the water is going to tend to run out. Kind of like squeezing a sponge.
How close to the wall was the torn-off roof? Was it piled in one big pile, or spread out over a large area?
Pretty much of a big pile a few feet from the wall. Can that weight be transmitted to the fluid in the ground and raise its pressure on the external basement walls? Could that weight be responsible for increased humidity in the basement? Doesn’t seem right, somehow.
Did they pile the stuff carefully, or drop it like a 2 foot diameter tree limb from 50 feet?
The later can make a pretty big divot by compressing the soil where it hits.
It was a roof tear off, so it came off in pieces lighter than a tree trunk. But it did pile up.
If you put weight on cube of saturated soil, yes, the water will move out of the soil.
Consider the concept of a ‘natural spring’. This occurs when groundwater, which is moving through soil, pops up out of the ground. Springs can flow at some fairly good rates. ISTR a thread where Harmonius Discord describes a spring on a relative’s farm which gave water for many, many years.
Now, in the case of the pile of old roof, whether groundwater will move at a rate of some inches per hour, or some inches per century, is a function of the permeability of the soil (and of course the weight of the pile o’ roof). Of interest also is the saturation of the soil.
Also to be considered is the permeability of the basement wall itself.
Considering the soil to be saturated with water, if this soil were sand, AND if the basement wall was porous, then yes I think you’d see an increase in the dampness on the inside of the basement.
However, if this soil were clay, AND the basement wall was fairly impermeable, then no I don’t think you’d see an increase in the dampness of the basement wall this century.