loft

[astidham]

I'm building a 20x30 single story with 10' side walls and I want to put a loft over the bedroom and bathroom area.
there will be a wall 14' away from the outside wall for the bathroom, what size floor joist and what spacing would work for this?
I will be using this area as a bedroom.

[rocking23nf]

2x10 16 inch on center, #2 or better spruce.

[dug]

This calculator is handy -

http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

It would tell you that a 2 by 10 would work for 24 in. spacing as well, but that is the limit. I usually feel better about going a notch or so above the minimum so I vote 16 in centers also.

[astidham]

Thank you

[astidham]

I didnt mention that the wall 14' away is not a load bearing wall just an interior wall.
the total span is 20' without the wall, can i still use a #2 df 2x10?

[Don_P]

Not without turning it into a load bearing wall. The span is ~19' or you need to support that wall to the ground.

[astidham]

Thank you Don_p, what is normaly used for a loft in the 20x30 plans? I have the single story plans.
I know the floor joist are a 2x12 but i was looking at the head height lost, which is not that much I know.
if i use 2x12s for a loft do the need 16" o/c spacing or will 24 o/c be ok for a loft bedroom?

[Don_P]

I don't have a plan.
It looks like you need #1 Dougfir or SYP 2x12's at that span or Select Struc SPF lumber at 16" on center.

If I understand your plan the lower floor girders are slightly inboard shortening their span as compared to this span from wall to wall.

[astidham]

Yes Don_P these joist would span over the top plate of the bathroom wall.
Thank you for the info for the 2x12

[John Raabe]

You can safely use the same floor joists that are called out for the main floor. They would have the same span. I show both high quality 2x12's and engineered I-joists.

[astidham]

Thank You John

[astidham]

is there a more decorative beam i could use for the loft, these beams will be exposed.
4x8?

[dug]

I am using rough sawn 4 by 8's for my loft but I have a supporting wall at the halfway point (10 ft.). To span the whole distance I think (not sure though) you would need 4 by 12's. The beams I got were not graded so if you are dealing with inspections they would not be an option. Probably there are alternatives though.
20 ft. is a large span and a 4 by 12 or better that length will be very heavy!

Usually large beams are spaced farther apart and have heavier (2 by 6) decking which looks nicer

[astidham]

Thank You dug, That is what i would like to do is have larger o/c spacing and a hardwood floor on top.

[Don_P]

What species are available to you in heavy timber?
Is there any way you can back up and make that midwall load bearing?
I've been planing 6x8x12' locust this morning... I don't feel real good at the moment.

[astidham]

Hey Don_P not a lot of options i have found so far other than #2 doug-fir around here.

[dug]

Is there any way you can back up and make that midwall load bearing?

I second that thought. Seems like you might not be too far along to provide support for a load bearing wall there. It would be some work but might make things easier in the long run.

[astidham]

dug,in your opinion could i use deck blocks and an additional 2x12 built up beam just running the 10'8" under the bathroom wall? (20x30 single story plans)
i dont think i could dig at this point for a footer.

[dug]

I got to thinking after I posted my comment, I would guess you would have to have footers on the supporting piers or else you may experience uneven shifting during a freeze.

It probably would be pretty difficult to do since you already have the joists (sheathing also?) down.

You may have to do a little research to find out what sort of beam would handle that span using the spacing you have planned (3 ft?).

[astidham]

I will probably just span the under 20' distance with 2x12x20' on 16" centers.
I do thank you for your help!

[Don_P]

I'm going to say this very quietly, if there is no water there is no frost heave potential. I have cut the handle off of a shovel and dug where I couldn't turn over before. Makes for a long day but can be done. A shallower footing can be frost protected somewhat by covering it with foam insulation and earth.

A 4x12 #2 Dougfir with just under a 20' clear span and 30/10 psf load just squeeks by at 32" centers.

[astidham]

thanks Don_P