loft joist size

[nysono]

Hi all,

Things are progressing towards finalizing my camp plans but I would like to change the loft floor joist sizes and cant find a calculator that will allow me to change sizes.  By using the calculator posted by Don P (thanks by the way) I need a 2 x 10 to span the 12 feet (2' OC) to the center load bearing wall (camp size is 24 x 32).  I would like to use rough cut 4 x 6 (to keep a rustic look or similar), any thoughts. subfloor will by 3/4" advantech. 

Still 18" of snow on the lot but it is going away slowwwwwwwwwlyyyyyyy. Hopefully by May 1 I can get footers poured.

Thanks
Steve

[Don_P]

Hi Steve,
I'm not sure which calculator you are referring to but I'm guessing the AWC span calc.The AWC website also has the WSDD manual online that has safe load tables in it for various timber dimensions. I've written several that do allow you to input custom timber dimensions but they are not as easy to use;
http://windyhilllogworks.com/Calcs/beamindex.html

[nysono]

thanks Don P....you are right the windyhilllogworks are not very easy to use unless you know alot more than I do.

[Don_P]

A 4x6 is a pretty shallow joist at that span, we can do the math and see but more than likely it needs to be a 4x8. Is there anything else bearing on the floor from above... 2nd floor or roof supports or something heavy? I'm assuming you could make it through the awc calc ok, here's another method. Take theirs and set it up for 2x6 in the species and grade you wish to use and input 12" centers, that will give the same allowable span as if you use an identical species and grade of 4x6 at 24" centers. If anything input a lower grade if this is unknown grade sawmill lumber.

When you get to the output screen on the awc calc, look at the bottom. It will give the material properties my calc is asking for you to input. These will work on mine as long as the timbers are less than 5" thick.

[nysono]

Thanks Don P, I think I will be ok with 4 x 6 if I go 16 OC.  Im trying to keep as much head room in the loft as possible so I want to drop the ledger to to 7'6" and go up from there.  4 x 6's will be hemlock most likely.  There wont be anything significant above for weight excepts a couple of beds.  If I put up a partition wall it will be over the load bearing at the 12' center.

Steve

[Don_P]

I just checked it in eastern hemlock. at Full 4"x6" in #3 grade it does work on 16" for me. It also checked, for me, at 24" in #2 grade with full dimension material. Nothing wrong with going safe. 1" Hemlock subfloor with 7/16" osb above would make for a nicer ceiling IMO.

[Marty]

First post, so here goes...

I have 4"x6" rough sawn beams holding up my loft.  They are about 24" apart.  The important factor for me was ceiling/floor height and look.  I "improved" the spawn issue by topping it with 1 3/4" thick tongue and groove pine boards for the floor/ceiling.  No bounce when me and the dog are up there... ( I will post pic if I ever figure out how.)

[RIjake]

Marty, I'd love to see some pictures of your beams too.  I'd rather go bigger and spaced further apart if I can but it may not be possible.  BTW my loft floor will be 2x6 T&G spruce