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]

On Wednesday, October 31, 2012 10:28:02 AM UTC, wrote:

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]

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

On Oct 31, 11:03*am, wrote:
On Wednesday, October 31, 2012 10:28:02 AM UTC, wrote:
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]

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

Or put them in @ closer spacing than normal if you have plenty of
them. eg @ 300mm centres.

On 31/10/2012 10:27, george - dicegeorge wrote:
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

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,

Does the panel think the 3x3s will be OK,
how close to each other should I put them/

400mm c2c...

The loft will never be converted into a room.

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.


--
Cheers,

John.

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On 31/10/12 19:00, John Rumm wrote:
On 31/10/2012 10:27, george - dicegeorge wrote:
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

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,

Does the panel think the 3x3s will be OK,
how close to each other should I put them/

400mm c2c...

The loft will never be converted into a room.

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.


Thanks but plans changed tonight
when talking it over with a carpenter freind
and I realised that if I double up the 3x3s
with glue and screws
then I'd be able to use the loft for storing slates etc
when I come to repairing the roof and valley.

[george]