12x2 floor joist span.

[pete47]

Hi guys, I'm moving soon and we are going to convert the loft as soon as we are in. It has a nice high pitch so we could get away with 12 x 2 joists for the floor. I'm hoping we can get away with 1 rsj for the floor and 1 for the ridge but can't find anywhere the maximum span for 12x2's.

I know the structural engineer will advise nearer the time but I'm being impatient! Can anyone advise me on this or point me in the right direction?

 

[Jackrae]

An old (very old) rule of thumb for (n x 2) joist spans was 1/2 the span (in feet) + 2 ". Therefore for a 20 feet span this would work out at 10 + 2 = 12"

But I'm sure there are much more technical solutions on the go, which take into consideration all the variables such as joist material, joist spacing, floor loading, whether ends are built in or sitting on point loads etc etc.