I've been asked to fix a pair of moderately heavy loudspeakers (6-7 kg) to a steel framed stud wall in a school. Normally, in solid walls, I would use expansion bolts but obviously they would not be suitable here. Bearing in mind the location, safety is paramount. Any suggestions would be very welcome.
Use a timber to stick to the wall first. Use Gripfil adhesive (see our adhesives used at home project) as well as a Heavy Duty Redidrive plasterboard fixing (See our fixing to plasterboard project) in each corner of the timber also. Gripfil is a very strogn adhesive which will hold much heavier weights than thius and the fixings are simply to keep the board tight to teh wall and stop it slipping while the adhesive goes hard.