Timber joist calcs - can anyone help?

[andy43]

I have a beam and block floor, beneath which we'll have a void, then a plasterboard ceiling supported by timber joists.
What size timber do I need working on 4.0m clear span with no connection or help from the beam and block above, 400mm centres, no imposed loads - the 12.5mm plasterboard dead load only - so 0.2kN/mm2?
I can't find a free sizing calculator anywhere, and any load tables assume I'll be above the joists jumping up and down on them.
I know I should pass silver across the palm of my SE, but it's easier and quicker (and cheaper) asking on here.
TIA!

[andy43]

Beautiful, many thanks!! Forgot to say C16
Just to be a complete pain in the arse, would 150 x 47 C16 work?
As I may have a couple or three long enough lengths that I can use to get started

[andy43]

Great, thank you again, very much appreciated.
I agree with the over speccing of stuff - the quality of modern timber is frightening, whether it's got a stamp on the side or not.

[andy43]

This is what I came up against, hence the reason for the posting - there aren't any tables I could find that size the joists assuming zero imposed or point loadings.
They all assume my christmas decorations and dead mother-in-laws will be stored above.
6x2 seems cheapish and chunky enough, but not too heavy as to make it difficult holding the timbers in position waiting for the No-nails to set at both ends.
Kidding

[andy43]

TA14 said:

andy43 said:

This is what I came up against, hence the reason for the posting - there aren't any tables I could find that size the joists assuming zero imposed or point loadings.

That's because zero imposed loading is unrealistic. Ceiling loading is already very low. In your case what if step ladders collapse and someone grabs onto a joist, etc. ?

Then I, as chief plasterboarder, with suitable ladder training certification, would plummet 2.4 metres (+/- 10mm) to certain death, my fall only cushioned by liberally scattered polar bears and small children, placed there as part of 'H&S In the Workplace' EU directive Protection against wobbly ladders 39787f/663b (ii).

[andy43]

T'will be noggin'd at every board joint. 4.1m span so 1 and a bit 2.4 metre boards staggered should do it. And 6x2 seems decent enough. 12.5mm boards - yes, it should be 0.2kn/m2 not mm2.
Adding the self-weight of the timbers just confuddles things

[andy43]

My house, my call. 150x50 will do nicely.
But this is the reason I originally posted - the tables don't allow a ceiling without the assumption it will also have a crawl space above.
Thank you all