On Oct 21, 2:54 am, Lee B wrote:
I have a 50 yr old row house. Never had a water problem... except for
during Isabella, the sump pump didn't work and water backed up into the
finished basement. I dried everything out and didn't think much of it.

Fast forward 5 years, and I have the house up for sale. Buyer made an
offer contingent on mold test. (My agent didn't know why as she hadn't
noticed anything, other than it smelled a bit musty from the house
(vacant) being closed up. I have asthma to cats, dogs etc and never had
a problem). Test came back "high" for several types of mold, including
the starchy stuff. They also saw, but didn't test for, mold on attic
rafters. Buyer bailed.
+++++++++++++++++++++++++++++++++++++++++
Mould spores are everywhere!
Usually they are not a problem.
They only come to life when there is a damp place for them to settle
and grow.
Mould that is growing on something that is damp, dies the moment it
becomes dry.
Mould in the home, is the result, in the main of our living style.
We breath and sweat some 2.5 litres of water vapour each 24 hours,
this vapour is held in the air until the temperature drops, whereupon,
it heads for the nearest cold place, usually a window, where it turns
into condensation.
If there is a spot that is colder than a window then it settles there.
The cold spot may be a bed, wall, ceiling, furniture even the loft.
Water vapour (our breath is saturated water vapour) is an incredibly
tiny gas, think of it as air being the size of a football and water
vapour being tiny ball bearings that move between the footballs of
air.
Water vapour is so tiny it can find its way into most things, it can
certainly find its way through tiny holes in our woodwork.
After our breath and sweat the next things that produce water vapour
are kitchens and bathrooms, where things are left to dry on radiators
and the extractor fans are not used and where doors are left open.
There are two ways to get rid of water vapour.
One. Leave the windows open and dry the place out and wait for summers
warm dry days.
Two. Buy and use a de-humidifier, turn it on, leave it on until the
place dries out.

If you have a leaking roof or pipe the mould will be located near the
problem.

From what you write I guess it down to life style.
Perry