Push plug behind the plaster?

[JensHaglof]

Hello!
I need to mount a heavy sound absorber to the ceiling that spans the entire width of the room. It's supported by brackets on one end and by joists on the other. The walls are 2 cm of plaster and then porous lightweight concrete. (You can drive a long screw in without any problem)

I'm thinking of using these plugs for the brackets:
http://essve.se/webcatalogue/infastning-gips-stenmaterial/397480-lattbetongplugg/
10mm x 55mm

Should I push them in behind the plaster? Will I get better support that way? Should I fill up in front of the plug with something, like house fix or so? (because the last 2 cm won't be tight since the screw is 6 mm and the drilled hole is 10 mm)

Or is it enough for the plug to be flush with the plaster?
/Jens

 

[Mikael_L]

If the plaster is at least as hard as the lightweight concrete and adheres quite well, it carries as well as the lightweight concrete, and you can let the plug be flush with the surface.

But if the plaster is really poor, you get better load-bearing capacity in the lightweight concrete, then it might be better to drill a little deeper and get more of the plug into the lightweight concrete.