ItsMe wrote:
Hi folks,

My recently deceased mother in laws house is in the process of 'being
looked at by me' and due renovation.

A few years ago she had a grant for cavity wall insulation ( CWI )
and it was installed ( 82 yo and disabled ).

The installation used a blown in mineral wool type of insulation.

The property is about 100 years old.

On the front wall about 5 feet above ground level there is internally
a damp patch prevoiusly not identified - behind furnishings - and
it's not drying out. There are a few other damp patches here and
there above the 1 metre damp proof course fault boundary. Possibly
external mortar pointing also.
External mortar pointing/gutter downpipe leak in that area of the
wall was found to be substandard and is now fixed - but it's still
not drying out after 3-4 weeks.

What is the possibilty that the mineral wool insulation has become
sodden in the area and - given the lack of ventilation in the cavity
due to CWI - will take an age to dry out.

Today I have drilled the damp wall in 2 places from the inside to try
to recover some insulation to test for soddenness - can't recover any
insulation to test - just couldn't hook it out.

Maybe I need to remove a brick on the inside to gain access.

Is the mineral wool insulation they use water repellant or can it
become sodden and retain the dampness for long periods.

What are the implications for other external walls in the property
being that I've identified several areas externally where pointing is
defficient.
I have nightmares of sodden CWI in various pointing deficient areas
that would be verry difficult to fix without removal of the CWI.

Should mineral wool CW insulation actually have been used in this
situation where external pointing was in some need.and would have
been obvious at the time it was installed.

I know there are other possibilities for the damp in other areas but
in THIS area the wall above is not damp.

How to fix it - thats the question.

Recommendations welcome.

TIA - It's me

As others have said, it takes months to dry out brickwork.

It's unlikely that the insulation is wet because it's treated with a
silicone waterproofing agent during manufacture, this however, doesn't stop
water from tracking across the top of it if any voids are in the insulation,
which is why all walls have to be filled right up to the top - if any voids
/are/ left, the water can run down the inside of the exterior brickwork and
on top of the insulation and into the interior brickwork, if the insulation
goes all the way up without any voids, the water continues it's course down
into the foundations.

If you really want to get to the bottom of it quickly and don't wish to
wait, simply take down the section of interior brickwork and have a look
inside - if there is a void, fill the area with cavity batt insulation and
brick up with dry bricks and plaster over.