I plan to put in DIY damp course with injection gel on a ground floor bathroom wall and need to make sure my plan isn't flawed. The wall is rendered on the outside and, since I need to replace the salt-damaged internal plaster anyway, I'd like to leave the external render in place, take off internal plaster, inject the gel from inside the house, and then have damp-proof internal plastering redone after that. Is this advisable or do I need to replace external render layer too?
To complicate matters, previous owners had water supply pipes dug into this wall internally just above skirting board level, and plastered over. So long as I apply the gel below the level where pipes have been dug in, will the damp proof gel still do it's job? Thanks in advance for any advice you can offer.