Annoyingly there’s no cavity, the board is laid on top of a single skin brick wall (conservatory). I’ve picked up something similar to Airheads suggestion, will report back
yeah the name is misleading but from my experience (and I seemed to remember Fischer’s own specs) they don’t need a cavity, the metal ‘umbrella’ still expands in the foam insulation and pulls tight behind the plasterboard. Tho I had 100mm and studs in front of a brick wall.
Annoyingly there’s no cavity, the board is laid on top of a single skin brick wall (conservatory). I’ve picked up something similar to Airheads suggestion, will report back