3x3" on 7foot span ceiling ?

Question

I have a lot of 3x3s from old pallets, 70mmx70mm, and spans of upto 2.2w1 meters for my bedroom ceiling.

On top I plan to put a layer of kingspan, and then Ply or OSB, then use it for storage.

Tony Brier wrote: Our old rule of thumb when I was a BCO which matched the tables pretty well was that for floor joists is double the depth in inches and subtract two to get the permissible span in feet; Which would give 2"x4 1/2 " for a room floor

Does the panel think the 3x3s will be OK, how close to each other should I put them/ The loft will never be converted into a room. [george]

meow2222 · Accepted Answer

It'll work. I wouldn't though, I'd glue & screw them to make 2x6s.

If for some reason you do it with 3x3s, 3 rows of noggings supported at the ends would help. Its easier to precut all the 13" noggings.

NT

harry · Answer

e:he ends would help. Its easier to precut all the 13" noggings.Or put them in @ closer spacing than normal if you have plenty ofthem. eg @ 300mm centres.

John Rumm · Answer

That is for floor joists carrying a normal floor though, not for joists just carrying a ceiling.

Remember floors have to be designed to allow for the parties when there are 20 people in the room, or the bedroom with a row of heavy wardrobes all say on a pair of joists down one side, or the 250kg hot water cylinder or bath etc,

400mm c2c...

What you going to store on them?

at 0.4kN/m load (half what you would allow for on a real floor) you will only get about 5mm deflection on a 3x3 at that spacing used in that way at that span.

george - dicegeorge · Answer

Thanks but plans changed tonightwhen talking it over with a carpenter freindand I realised that if I double up the 3x3swith glue and screwsthen I'd be able to use the loft for storing slates etcwhen I come to repairing the roof and valley.[george]

3x3" on 7foot span ceiling ?

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