Mezzanine and joist span help?

[HunterDan]

Been trying to plan the mezzanine for my barn, and have a few questions/am stuck. Especially on the joist spans. So I'll start with that. My posts are 8' apart, and I would like to put the mezzanine in the corner. Ideally I would like to go out 2 poles, and down either 2 or 3, so 16x16 or 16x24. I plan on using the space for storage of tools I don't use often, and possibly a small work bench/area for tuning my archery equip.

If I used 2x12 joists spaced 12" oc, could I span that 16'?

for attaching the joists, could I use a ledger board, lagged just to the posts and regular deck joist hangers?

For the garage side, can I just bolt a bracket to the floor, and attach the post to that? A friend of mine keeps telling me i need to cut the floor and dig down/pour a footer.

Thanks for any tips!

 

[jeepermat]

2x12x16 can be spanned 16' on 16" centers for a 20lb dead load, 100lb live load.
12" center is probably overkill for your span.

Attaching your joists is exactly how I built mine.

For the post on the floor how thick is the floor currently? For my mezzanine I just pinned a 6x6 post onto the concrete and called it good, I never had any issues. If you are going to put loads of weight up there, and have a large span-fewer posts, then you might need to dig cassions.

 

[HunterDan]

Thank you! Glad to know I can make this work.

The slab is 6" for a majority of the floor, minus a 20x20 section where I'm going to eventually have a lift, we poured 8" plus.

I figured 6" would be plenty, and I wouldn't need a footer. I will be keeping that side mostly open, w/removable railings so I can lift heavy things up there with my tractor

 

[matt_i]

If you reason that a corner post is going to take 1/4 of the vertical load on the rectangle, 16x24 is 384sf, /4 = 96 sf. If you go with the 20#/sf dead load, you're going to only be into 1920 lbs. If you used a 6x6 it works out to 63psi on either the wood or concrete floor. Obviously there is more load due to the framing, but if one doubled the loading, I still think 120psi is well within reason for wood or concrete or even the soil below without special prep.

 

[HunterDan]

So I would be good just using 6x6 post's for the garage side support, attached to the floor with something like this?

 

[big.jim]

they do one of those with a spike on bottom so just drill a hole and place in position

 

[K'ledgeBldr]

It all sounds fairly reasonable. However, on the ledger board there will be only three attachment points- ends & middle. By just thru-bolting these you're putting bolts in a shear position. And you're also putting lateral load on the posts the were designed for vertical load.

So, with that said I'd reconsider your load attachment points- making it free-standing with its own vertical support posts.

 

[lakeroadster]

Hey Dan, check these span tables out: http://www.southernpine.com/span-tables/joists-rafters/

The type and grade of lumber you use and the expected loading will drive the design.

 

[HunterDan]

It all sounds fairly reasonable. However, on the ledger board there will be only three attachment points- ends & middle. By just thru-bolting these you're putting bolts in a shear position. And you're also putting lateral load on the posts the were designed for vertical load.

So, with that said I'd reconsider your load attachment points- making it free-standing with its own vertical support posts.

I was wondering about that. I've heard of guys doing it both ways, and haven't really heard of any issues by doing it either way.

I'm assuming free standing would be my best bet?

 

[jeepermat]

Mine is a mix of freestanding, and attached the the building for support.
Vertically it is completely supported by its own posts, I have attached it to the building where possible just cause.

 

[maverick3316]

Or just use steel.

 

[HunterDan]

The steel is nice, id lose less headroom, but At what cost? How much more would steel be, over wood?

 

[maverick3316]

The steel is nice, id lose less headroom, but At what cost? How much more would steel be, over wood?

I don't really know what the cost would have been. Everything used to build it was extra stuff we had laying around the shop (less the plywood, thats new)

If I had to guess, maybe $1000 (+/- $200). The columns are HSS4x4x1/4", the beams are W6x9, and the joists are 10" deep.

If you go to a local steel fab shop, they might have stuff laying around they might sell you for scrap prices. You might even get them to install it and everything. Steel guys are always looking to make a few extra bucks.