Hi,

Could anybody who has access to the regs for unsupported timber span
sizes, give me an idea as to what size timbers I need for a floor? It
will be 3300mm between supports, spaced at 400mm, and will be used for a
shed / workshop (no particularly heavy equipment, just desk / chair /
electronics workbench etc).

Floor on top will be 18mm bitumenised OSB, with insulation between the
joists.

If I increase the spacing to 600mm, does that make much of a difference?

Thanks for the help

Gary

My unsupported span is 4.00 metres and old fashioned 7 x 2 inch joists
were used. This is a loft area and not walked on. To convert the area
into a living room the joists should be 9 x 2 inch or the new metric
equivalent.

Have a look here, there's a lot of info inthis site....

http://www.roofconsult.co.uk/

Chris.

Minimum seems to be 50 x 170 C16 grade @ 400 or 450 c/c.
At 600 c/c span is given at 3290, but this may be a little too bouncy.

50 x 200 will be OK @ 600 c/c.

dg

In article .com,
says...
Minimum seems to be 50 x 170 C16 grade @ 400 or 450 c/c.
At 600 c/c span is given at 3290, but this may be a little too bouncy.

50 x 200 will be OK @ 600 c/c.

dg



Thanks very much - just what I needed.

errm, 50x170 - that's 7x2 isn't it? ;-)

Sorry I don't speak imperial, but grandpa says its 7x2.
:-)

dg

Gary Cavie Wrote:
Hi,

Could anybody who has access to the regs for unsupported timber span
sizes, give me an idea as to what size timbers I need for a floor? It
will be 3300mm between supports, spaced at 400mm, and will be used for
a
shed / workshop (no particularly heavy equipment, just desk / chair /
electronics workbench etc).

Floor on top will be 18mm bitumenised OSB, with insulation between the
joists.

If I increase the spacing to 600mm, does that make much of a
difference?

Thanks for the help

Gary

The "old" way to do it, and in imperial, is half the span ( in feet )
plus an inch,
so for instance a 12' span would be half 12 = 6, plus 1 = 7, so 7 x 2
joists. That would be at 16" centres.
I know there are all sorts of regs/charts/tables etc but this is a
useful rule of thumb.


--
Nick H

Gary Cavie wrote:
Hi,

Could anybody who has access to the regs for unsupported timber span
sizes, give me an idea as to what size timbers I need for a floor? It
will be 3300mm between supports, spaced at 400mm, and will be used for a
shed / workshop (no particularly heavy equipment, just desk / chair /
electronics workbench etc).

Floor on top will be 18mm bitumenised OSB, with insulation between the
joists.

If I increase the spacing to 600mm, does that make much of a difference?

Thanks for the help

Gary
In Impeial peak, the rule of thumb is that, for a 2 inch thickness, at
16inch centers, the size (in inches) is the span (in feet) divided by 2
plus 1. e.g for a 12 foot span, 12/2 =6 +1, so a 7x2 joist is needed. I
stress that this is a rule of thumb.
Malcolm

errm, 50x170 - that's 7x2 isn't it? ;-)

175mm x 50mm is 7 inches by 2 inches ... BUT.. you may find you've
been sold 165mm x 47mm instead when you come to actually measure it.
Also I used C16 but found that three out of the fourteen that I'd
bought did warp badly in the 165mm. direction. If I was doing it again
I would use Redwood. It just feels a lot stronger than the C16. Also I
was exposing the underside of the joist by setting the 12mm.
plasterboad back by about 35mm. to give a slightly old fashioned look
to the ceiling.

Chris.