I have removed a partition wall in the house. Where the wall met the outer wall, there is a large gap (20mm) between the plasterboards with insulation in them. Behind the insulation, there is a rubber strip. I was planning to fill the gaps with foam and then plaster over it. But now it's clear that it's an expansion joint for the house. I need to do something to tidy it up a bit. I've tried to find an expansion joint strip to plaster in but can't find anything. What can be done here?
