independent ceiling span of 4m, 400 centres, size of joist?

[Casterbridge]

Independent ceiling at 400mm centres, span of 4m. Will hold 2 x 12.5mm fireboard - total plasterboard weight 20kg/m3. Also some insulation taking the total static load to less than 30kg/m3. No live load as the floor will remian in situ above.

Are there any tables for the size of ceiling joists for the ceiling for c16 or c24 timber. I can only find floor joists, not ceiling joists (I assume the pure static load will allow me to use smaller joists that for a floor?)

 

[noseall]

Use 100mm x 50mm with a central binder strapped to the existing ceiling joists.

 

[tony1851]

The older editions of Approved Document A have the tables for ceiling joists.

Looking at mine it says 7x2s C16 would be OK for 3.72 m for dead load 0.25 to 0.5 KN/sq m. (your 2 layers pb'd will fall in this range).

But these figures allowed for a small live load (loft storage) of 5lbs/sq ft,
so you should be well-OK on a 4m span with no load other than dead load.

Or cheaper as Noseall said to use smaller joists and suspend mid-span?

 

[Casterbridge]

Thanks guys - would rather not strap if possible.

Been trying to search the internet and found this interesting document.

http://www.fdean.gov.uk/media/Asset...ents/EXTENSION_GUIDANCE_JUNE_2011_AMEND_2.pdf

Page 36, Table 11, says a 7x2 will span 4.07m for C24 - but I'm not entirely sure this is a correct table to use, and would rather find the source ?!?

 

[tony1851]

That's about right - my table for C24 on that span says 3.99m.
But C24, although a stronger timber, does have a tendency to twist slightly - more so than C16.
If you don't want to use hangers, just use 7x2s @ 400.

 

[freddiemercurystwin]

The tables and the info on the PDF you linked to is all taken from the original TRADA span tables so is reliable. 7x2's as mentioned will be fine.

The old 1992 version of the building Regs Part A is available to view on the Planning Portal.

 

[Casterbridge]

OK Cheers - I also foudn this :

http://www.constructionproducts.org...ilename=Domestic_Extensions_Project_Guide.pdf

Which confirms the size on Page 84 - Table 6.3.

How would you recommend I attach the joists to walls? Attaching timber with coach bolts? If so what size timber, coach bolts and distance between bolts?