Browse Forums Owner Builder Forum 1 Mar 07, 2012 6:46 am Our designer has specified "no penetrations" for the lighting in a couple of rooms as we are a little obsessed with energy efficiency (flat roofs, not much ceiling space). But we don't like the look of most surface mount LEDs housings & don't want pendants everywhere. For these 2 rooms we have high ceilings (3.4m or so I think it is), so I was thinking we could install the insulation between the rafters & cover it with plywood/plaster/something & seal the gaps with "no more gaps". Then put in a 100-150mm dropped plaster ceiling - this would allow us to install LED downlights & also make it easier to run the cabling, transformers, etc. So my questions are; - what would be the ideal material to cover the insulation/rafters with? Was thinking maybe plywood? - is this a good idea or asking for trouble somehow? eg, Is it easy to keep the plaster flat on a dropped system? Re: Dropped ceiling - plywood or plaster? 2Mar 07, 2012 8:21 am suprok So my questions are; - what would be the ideal material to cover the insulation/rafters with? Was thinking maybe plywood? I presume you mean hold up the Insulation , not cover it. Thus something would go under the Existing Ceiling Joists. Better than over so you could see the joists to walk on and the insulation can be held in between them. Gyprock would probably be cheaper than plywood in doing this suprok - is this a good idea or asking for trouble somehow? eg, Is it easy to keep the plaster flat on a dropped system? A drop ceiling is basically the same as a normal ceiling, however instead of the joists sitting on a wall plate, bearers are bolted to the walls at a lower height. Then joists nailed between the bearer plates So as far as keeping it flat it wont make any difference However in my honest opinion if you are doing this purely for Energy savings it seems a bit OTT. The embedded energy in extra construction may end up outweighing the heat loss from a few LED down lights (Not that I have the maths or capability to prove that just a guesstimate and especially as LED downlights only need a 2cm Insulation clearance unlike Halogens which I think is 20cm all round) It certainly is a common aesthetic thing to do but from your post that seems not to be your driving factor. The other consideration is you will probably have to build the ceiling in 2 stages. ie Build the first ceiling at plate height, run in electrical, line it with gyprock, then put in your drop ceiling frame and install. Otherwise you wont be able to get your Gyprock sheets through the remaining gaps of the joists and frame. All possible to do just adds to the $$$ https://forum.homeone.com.au/viewtopic.php?f=38&t=44762 My Owner builder journey extending a 1930's Bungalow Re: Dropped ceiling - plywood or plaster? 3Mar 07, 2012 9:06 am If it were me, I would have R1.5 builders blanket under the roof then drop the ceiling using something like this http://www.rondo.com.au/Literature/KEYLOCKConcealedCeilingSystems.aspx then I would lay the insulation on top of the rondo then fix the plasterboard to it. Or if you want to fit the insulation between the rafters just secure it with chicken wire or similar to stop it falling out. Re: Dropped ceiling - plywood or plaster? 4Mar 07, 2012 9:33 am Thanks guys, great info. docker_rob I presume you mean hold up the Insulation , not cover it. Ah, yes this is what I meant. docker_rob However in my honest opinion if you are doing this purely for Energy savings it seems a bit OTT. The lining will also used to improve the accoustic properties of the room as well - the walls are all insulated concrete forms, so the roof will be the "leaky" bit, both thermally & noise wise. Possibly a bit OTT, but I'm thinking the dropped ceiling will also make chasing the wiring much easier (plus cat6 cables, etc). I know it's 'doubling up', but originally we were going to install 2 sheets of plaster to deaden noise anyway. I don't mind the extra expense; just want to ensure I do it the right way! andy the pm If it were me, I would have R1.5 builders blanket under the roof then drop the ceiling using something like this http://www.rondo.com.au/Literature/KEYL ... stems.aspx Thanks, that system looks perfect! Re: Dropped ceiling - plywood or plaster? 5Mar 07, 2012 2:20 pm suprok The lining will also used to improve the accoustic properties of the room as well - the walls are all insulated concrete forms, so the roof will be the "leaky" bit, both thermally & noise wise. Possibly a bit OTT, but I'm thinking the dropped ceiling will also make chasing the wiring much easier (plus cat6 cables, etc). I know it's 'doubling up', but originally we were going to install 2 sheets of plaster to deaden noise anyway. I don't mind the extra expense; just want to ensure I do it the right way! For acoustics you may also want to consider "Gyprock Soundcheck" - Only a few $$$ more per sheet compared to standard Gyprock, and from what I have heard works very well for reducing noise transfer. One of the Members on here put me on to it and I am planning on using it myself to lessen noise from an upstairs loft. https://forum.homeone.com.au/viewtopic.php?f=38&t=44762 My Owner builder journey extending a 1930's Bungalow Jimbo73 I would use heaps of adhesive on each sheet and screw rather than nail. use as many as you like cheers Simeon 1 4075 Our 6m high Cathedral ceiling has 0 insulation, just plaster, wrap and tiles as far as I can tell. 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