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Ceiling Joist Sizing

Postby mapearce » Fri Nov 13, 2009 8:42 am


I am putting a new independant ceiling below the existing ceiling in my living room. I live in a ground floor flat. The span is 3.8m across the room. I want to put the joists at 400 c/c. There will be no load from above as its indepandant. I am going to fix 2 sheets of plasterboard (12.5mm and 19mm) to the underside of the new joists and then skim.

Can anyone help with the sixe these joists should be?

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Postby bd3cc » Mon Nov 23, 2009 10:53 pm

are they fixed to the ceiling above or suspended?
why 32mm of plasterboard. if for soundproofing dB chech and high density insulation?
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Postby Timberjack13 » Sat Dec 19, 2009 10:48 am

HI, if there is no weight on the new joists then 6 x 2 should be ample, u could prob get away with even smaller timbers, id dry line screw the 12mm plaster board to the joints...joints should idealy be inbetween 400--600 centres! and then skim over

Is it just a case of lowering the ceiling?
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Postby Perry525 » Mon Dec 21, 2009 6:46 pm

There are tens of thousands of homes with twelve foot wide rooms where the traditional 4 x 2 inch joists have been in place as ceilings/floors for lofts, for over a hundred years, many are loaded with many things. You can add to this the weight of people walking across the lofts as well.
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Postby claridge » Thu Feb 04, 2010 9:29 pm

I would suggest a 4x2 be more than sufficient ensuring the joists are fixed mid span from the existing ceiling/flooring joists of the flat above. This fixing could be in the form of a hanger that enables the the ceiling to be much lower then 4 inches,the depth of the the new joists.
If the ceiling is completely independant obviously always span the shortest distance and consider a 6x2 but ensure the wall plate timbers (boundary ) are resin bolted to the masonary as the net weight of the ceiling as a whole with plasterboard and skim is cosiderable.
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Postby TheDoctor4 » Mon Jun 28, 2010 9:02 pm

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