Can anyone please advise regarding expanding foam issue?
We have an ants nest in our cavity wall. We’ve got to get rid of that first of course, but then we have to prevent re-infestation.
The house is 27 years old, standard construction, with concrete floor and dry lined walls. Some years ago we had a ground floor window converted to French doors, and the installers cut the brickwork down to floor level, and fitted an internal wood sill over the cavity gap. Through a gap in the sill, removing the moulding covering it, I can see cavity wall insulation polystyrene beads.
The nest is centred below the sill, but also extends into the wall either side. We are gradually cementing/sealing all the exterior cracks as we find them, and using chemical and bait methods to try to get rid of the nest (we may have to call in pest controllers on that).
Once clear, is it OK to squirt expanding foam into the cavity wall gap below the sill to seal this area, or would this affect the DPC two courses below?