Loft

[78T/A]

Hey guys.
Been a while since I posted. I'm wanting to build a loft in my shop that I have rented in the very back. I plan to build it out about 10 ft. and span 20 ft. I don't want any posts in the middle as I need the room for my T/A. under it. I'm wondering what size wooden beam to use that'll span 20 ft. It has to be free-standing also. Thanks

 

[purediesel]

Google yellow pine span chart.

 

[78T/A]

Thanks but this is Greek to me.

 

[Kaizen]

Too long. Can you put a post at 12 feet?
What are you putting up there? Depth depends on load as well. At least a 2x10.
You can do the 20 maybe with an lvl beam.

Suggest you start reading or your TA might get crushed.


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[Dagny]

I'm going 18 feet with doubled up white oak 2x12s

 

[78T/A]

Ok, What if I put a post at 3 ft. on each side? That would leave a span of 14 ft. I'm not putting a lot of stuff up there and definitely not heavy. I don't have a good way of getting up there anyway. I'll have to figure out some sort of steps or a pulldown ladder. I plan on using 2x6s on top of the beams on 16 in. centers and 7/16 OSB sheeting. There will be a center post in the rear. I'm just trying to leave the front as open as possible.

 

[matt_i]

Your best bet is probably a pair of LVLs, some joist hangers and a pile of 2x8s or 2x10s and then the decking, 3/4" if you want to use 24" oc joists.

It would be supremely helpful if you could somehow attach it to existing structure rather than just create a freestanding deck. Wood blocking (spacers)
to take up side-clearances, held back to the structure by 2" wide ratchet straps would be very nice and easily removable in the future. Could also use wooden wedges with some care.

Heavy gussets to the legs in both directions as I'm guessing those are just sitting on the floor and not moment-bearing.

 

[78T/A]

I was thinking of just setting the joists on top of the beans.

 

[quickfarms]

My old loft was 8’ wide and 12’ long in the middle of a 24’ span

Double 1.75x16 microlams, 2x8 at 12” oc

Engineered floor load was 160 psf if I remember correctly

 

[Kaizen]

I was thinking of just setting the joists on top of the beans.

No. Must be attached front and rear with hoist hangers. It’s a huge space. Build it to hold a lot.
This needs to be tied into the building as well. If you don’t own this building you better ask. If built wrong and collapses this can take down the building. Google deck collapse.


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[78T/A]

I don't own the building but he said it was ok. I'm assuming you mean joist hangers.

 

[CraigStu]

I have never understood the fascination w/ joist hangers. I'd much prefer to sit the joist on top of the beam. I don't like running 4-6 nails into the joist 1" in from the end like most joist hangers are made.

 

[Innovate1]

Sitting on top of the beam is as good or better than joist hangers. The joists need to be tied to the beam and also to the back wall somehow to keep the beam from spreading from the back wall. Usually this would be a 2x attached to the back wall studs and then joist hangers but that may be more permanent than you want. Tie the beam support posts to the walls too but that can be something easily removed.

7/16 is thin flooring. I have used it for attic cat walks but that's not got anything stored on it and occasional use. I would go with at least 5/8 plywood.

What are you planning to store up there? Really makes a difference in loading calculations.

 

[Mainiac Mat]

If your roof is robust enough, you could use chain (5/16" would do the trick) and turnbuckles and support the beam from the ceiling framing. If you lag bolt a stout plate (2x10) into three of your attic floor boards, then hang your chain from an eye bolt (1" dia. machine threaded, passing through the plate and secured with heavy fender washers and double nut).

Take up the slack with the turn buckles to level the beam when under load and keep an eye on your ceiling to ensure it doesn't sag.

 

[Kaizen]

I have never understood the fascination w/ joist hangers. I'd much prefer to sit the joist on top of the beam. I don't like running 4-6 nails into the joist 1" in from the end like most joist hangers are made.

In this situation I’m thinking it will save room if he has 12 foot ceilings. Using hangers will save half a foot of height to ceiling.


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[firebirdparts]

Is this platform 10 by 20? I think everybody is assuming so, but I was wondering if you meant 10' high instead of 10' long joists.

That's not huge, and you can clear span that with gluelams, or steel, or a truss. You can span it with 20' long framing lumber (if you can find it) but it's pretty weak. The span tables to go to 20' at loadings like 20 psf and therefor it's possible to hold up a light load with framing lumber. Certainly not usual to do it that way.

 

[78T/A]

Thanks, everyone.
Yes, it's going to be 8 to 10 ft. wide by 20 ft. long. The ceiling itself is a good 15 ft. high so I have plenty of height to work with. The back wall blocks while the sides are covered in metal. It was a huge warehouse that was chopped up into bays usually for storing RVs.
Like I said earlier I may put a post about 3-4 ft. from one of the walls so I'll only have about 16 feet to worry about for the heavy beam.