loft floor joist span

CjAl · August 15, 2012, 09:49:25 PM

am i correct in thinking if i have a ceiling from the loft that has beams 4' on center i can measure the required 7' minimum height to the bottom of the loft flooring up inside the joist bays rather than to the bottom of the joists? am i reading the code correctly?

none of the floor joist calculators work for 4' on center or anything other then 2x material. could someone point me to where i could find a calculator or just tell me what sive beams i would need 4' on center to span 9'7" with a 30lb live load?

also can t&g 2x span that 4' between beams?

UK4X4 · August 15, 2012, 11:10:47 PM

I level forte software its free

you'll need to spec the flooring depth as well as the beams to get the "pass"

If you need help let me know I've been playing with it for months

August 16, 2012, 06:12:27 AM

thanks. i am on the road with just my tablet so i cant diwnload any software. guess i will look.into.it when i get home to my pc

UK4X4 · August 16, 2012, 09:01:33 AM

PM me your e-mail and I'll send the results through if you want

4x8 southern pine no 2 passes
4x8 hem fir no 2 passes
4x8 douglas fir larch no 2 passes

Erin · August 16, 2012, 09:29:34 AM

Quotealso can t&g 2x span that 4' between beams?

Yes.

August 16, 2012, 10:12:48 AM

I'm pretty sure the 7' minimum height applies to anything the head might strike ... so it would be to the bottom of the joists, if the joists are to be bare and not have ceiling material attached to them. Be sure to allow for finished flooring below.

CjAl · August 16, 2012, 02:15:58 PM

Quote from: JRR on August 16, 2012, 10:12:48 AM
I'm pretty sure the 7' minimum height applies to anything the head might strike ... so it would be to the bottom of the joists, if the joists are to be bare and not have ceiling material attached to them. Be sure to allow for finished flooring below.

there is.definatly an exception for open bays not less then 4' oc but there is something worded oddly about max 6" depth that i dont fully grasp.

MountainDon · August 19, 2012, 08:29:18 PM

I'm with JRR on thinking the joist/beams bottoms would be what counts. Buy why not give us a direct reference to the part that is puzzling? IRC section number would likely do.

CjAl · August 21, 2012, 10:37:52 PM

i have been away a few days. i will try to find it again. i actuslly found the part of the code originally in one of your posts mountainDon.

August 21, 2012, 10:52:57 PM

here it is
you were concentrating on the third exemption for sloped ceilings in this post but what intrests me is the first exemption. i guess by saying not more then 6 inches means beams if four foot apart can be 6" below that 7' min. but what type of 6" tall beam is good for ten foot span on four foot centers? thats asking a bit much i think of even a 6x6 but joist span calc dont list larger then 2x material.

do you think a 6x8 as example would satisfy that exemption as long as it didnt hang lower then. 6' 6"?

Quote from: MountainDon on February 24, 2011, 05:03:51 PM
R305.1 Minimum height. Habitable rooms, hallways, corridors, bathrooms, toilet rooms, laundry rooms and basements shall have a ceiling height of not less than 7 feet (2134 mm). The required height shall be measured from the finish floor to the lowest projection from the ceiling.

Exceptions:

1. Beams and girders spaced not less than 4 feet (1219 mm) on center may project not more than 6 inches (152 mm) below the required ceiling height.
2. Ceilings in basements without habitable spaces may project to within 6 feet, 8 inches (2032 mm) of the finished floor; and beams, girders, ducts or other obstructions may project to within 6 feet 4 inches (1931 mm) of the finished floor.
3. For rooms with sloped ceilings, at least 50 percent of the required floor area of the room must have a ceiling height of at least 7 feet (2134 mm) and no portion of the required floor area may have a ceiling height of less than 5 feet (1524 mm)..

JRR · August 22, 2012, 04:37:18 AM

Its not remarking about the beam dimensions, only its location. Its saying if the beams are spaced 4', or more, apart ... the bottom of the beam may be at 6'-6" above the finished floor. Or, at least, that's what I think it says.

A designer using this provision, and making a simple design, would probably find the balance of his ceiling much higher than the required 7'.

MountainDon · August 22, 2012, 09:10:41 AM

Quote from: JRR on August 22, 2012, 04:37:18 AM
the bottom of the beam may be at 6'-6" above the finished floor. Or, at least, that's what I think it says.

That's my take on it too

The beam sizing is a different question that is not readily answered by the usual tables.

CjAl · August 22, 2012, 10:00:11 AM

it was more clear reading it this time, i must have been overly tired the first time i read it.

i have access to some nice old reclaimed beams i think were 6x8 or mabey 4x8. there is also some larger ones but they get expensive. just not sure what i need to span ten foot. its just a sleeping loft overhead.

UK4X4 · August 22, 2012, 10:35:03 AM

Did you get my e-mail ?

I can do any 2x 4X timbers with the software- with 2x up to 4 plies and 4X doubles

August 22, 2012, 01:11:51 PM

yes i did but to be perfectly honest i was too busy when i got it and then i forgot. i will go look at it.