Looks like an original lead main coming in thereit does actually look like something is leaking in the corner.
dpc in the internal .
the lowest cement bed . 4” apart and 3/4 way through the bed.
I wouldnt bond a pb to tanking , unless it was an insulated board, and NOT using drywall adhesive.
reason :- no suction and no way for the adhesive to dry out , especially this time of year.
bond your insulated pb to external walls using low expansion , fill and fix foam.
or better still tank the external walls and batten and board.
and you need at least an inch gap between the board and floor.
a 2x1 treated timber would do . you don’t have huge amounts of damp so drilling the tanking shouldn’t be a problem in your situation .
the board is insulated one side which faces the wall.
the whole external wall and 1200 internals
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