I've cured most of the rising+penetrating damp in my 100-yr old house
house by raking out the cavities to below DPC-level wherever there was
a problem. The original slate DPC seems to be in good condition.

However, in one place, there is a 2-ft wide pier which was possibly
added after the original build. It was built into the cavity. (It is
9" thick, and stands proud of the inside face of the inner sking by 2"
and proud of the inside face of the inner skin by the width of the
cavity, i.e., it actually fills the cavity. It supports an RSJ which
runs accross the room at that point, supporting a first floor outer
cavity wall. The ground floor was extended forwards at some stage.
Hence the addition of the pier and the RSJ.

The pier has had a damp problem all the time I've owned the place, and
the damness can be felt up to a higher point than the other places
that had dampness.

How can I cure the damp in the pier? Chemical injection? The outside
of the house has been painted with Dulux Weathershield for the past 15
years, so I guess it cannot be the penetrating damp. I suspect that
the DPC was omitted from the pier, or they filled the cavity with
brick and mortar at the point where the pier was built and neglected
to add DPC to bridge the filled cavity.

If chemical injection might be the answer, can anyone advise where I
can obtain a DIY-er's kit - (preferably from a well-known DIY chain) ?

I could just paint the wall with damp-seal, but I would like it to
pass a surveyor's dampness inspection when I come to sell the place
shortly.

Thank you,

Mike D