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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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How do I calculate ceiling joist size and spacing ?
I'm installing an independent ceiling just below the existing one for
sound insulation purposes, so the only load it will carry is an acoustic quilt above and plasterboard below. Assuming maximum span of 4m and plasterboard thickness of 25mm, what size joists do I use and at what spacing ? Is there a generic formula I can use if I vary the span and plasterboard thickness ? |
#2
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How do I calculate ceiling joist size and spacing ?
On Oct 2, 6:58 pm, Señor Chris wrote:
I'm installing an independent ceiling just below the existing one for sound insulation purposes, so the only load it will carry is an acoustic quilt above and plasterboard below. Assuming maximum span of 4m and plasterboard thickness of 25mm, what size joists do I use and at what spacing ? Is there a generic formula I can use if I vary the span and plasterboard thickness ? Done this a number of times before ( its my day job)..... We always use 6x2 at 600mm centres unless its a really short span of say less than 1.5m where you might get away with 4x2. Normally we fix a wall plate using frame fixings, then fix the cross members directly onto them. Leave about a 50mm gap between bottom of existing cieling and top of new joist and you should be fine. You don't want any movement in your secondary ceiling, you don't want to go to all the effort and then it still fails to pass regs, so we always tend to over spec. |
#3
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How do I calculate ceiling joist size and spacing ?
Señor Chris wrote:
I'm installing an independent ceiling just below the existing one for sound insulation purposes, so the only load it will carry is an acoustic quilt above and plasterboard below. Assuming maximum span of 4m and plasterboard thickness of 25mm, what size joists do I use and at what spacing ? Is there a generic formula I can use if I vary the span and plasterboard thickness ? minimum size will be 2x2, but since you want acoustic insulation the bigger the better, preferably much bigger than 2x2. NT |
#4
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How do I calculate ceiling joist size and spacing ?
ch8rlie2000 wrote:
On Oct 2, 6:58 pm, Señor Chris wrote: I'm installing an independent ceiling just below the existing one for sound insulation purposes, so the only load it will carry is an acoustic quilt above and plasterboard below. Assuming maximum span of 4m and plasterboard thickness of 25mm, what size joists do I use and at what spacing ? Is there a generic formula I can use if I vary the span and plasterboard thickness ? Done this a number of times before ( its my day job)..... We always use 6x2 at 600mm centres unless its a really short span of say less than 1.5m where you might get away with 4x2. Normally we fix a wall plate using frame fixings, then fix the cross members directly onto them. Leave about a 50mm gap between bottom of existing cieling and top of new joist and you should be fine. You don't want any movement in your secondary ceiling, you don't want to go to all the effort and then it still fails to pass regs, so we always tend to over spec. Thanks for that. However, 6x2 doesn't leave me with much space for the acoustic quilt which is supposed to sit on top of the joists. Could I get away with 4x2 if I halve the centres ? |
#5
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How do I calculate ceiling joist size and spacing ?
Señor Chris wrote:
I'm installing an independent ceiling just below the existing one for sound insulation purposes, so the only load it will carry is an acoustic quilt above and plasterboard below. Assuming maximum span of 4m and plasterboard thickness of 25mm, what size joists do I use and at what spacing ? Is there a generic formula I can use if I vary the span and plasterboard thickness ? 4x2" at 400mm centres sounds like it ought to do it. You may find it helpful to have a play with the demo version of SuperBeam: http://www.sda.co.uk/sbw.htm Model a joist, and apply a uniform load based on how much weight you need to hang on it, and see how it performs. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#6
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How do I calculate ceiling joist size and spacing ?
On 2 Oct, 18:58, Señor Chris wrote:
I'm installing an independent ceiling just below the existing one for sound insulation purposes, so the only load it will carry is an acoustic quilt above and plasterboard below. Assuming maximum span of 4m and plasterboard thickness of 25mm, what size joists do I use and at what spacing ? Is there a generic formula I can use if I vary the span and plasterboard thickness ? The formula is that for a timber beam. It requires some engineering knowledge to do from first principles but there are bound to be tables available on the internet or in a library. Basically if it is lightly loaded as it is - just quilt and plasterboard and its own self weight - you will not need a huge depth for a span of 4 m. I have used 225 (9") for a similar span that is a floor load that will be reasonably highly loaded so 150 mm sounds about right to me at 400 cc odd. Any less and your deflection would be too great and dont forget duration of load effects if you go too small Chris |
#7
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How do I calculate ceiling joist size and spacing ?
Done this a number of times before ( its my day job)..... We always use 6x2 at 600mm centres unless its a really short span of say less than 1.5m where you might get away with 4x2. CLS equiv may be an alternative to consider 148 x 38 B&Q had a great deal on this ... cheaper than local timber yard .... great for this type of job as it's all gauged and planed. |
#8
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How do I calculate ceiling joist size and spacing ?
Thanks for that. However, 6x2 doesn't leave me with much space for the acoustic quilt which is supposed to sit on top of the joists. Could I get away with 4x2 if I halve the centres ? put quilt between on netlon support |
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