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Old 06-24-2014, 02:39 AM   #1
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


I have looked at a lot of span tables and calculators and am not sure if I can safely build this loft. It is in a garage and will need to bear the weight of two or three people and a build-in desk hanging off the wall. The ceiling is pitched, and clearance underneath is important. To maximize usable height underneath can I get away with a double 2x8 beam at 11 feet, with 2x4 joists (at 12'oc if needed) or do I need to do 2x6 joists? 2x6 ledger will be bolted to 2x6 studs, 4x4 beams anchored into concrete. Joists will be hung off hangers on both sides. 3/4" ply will be glued and screwed into joists.

Are these reasonable, safe plans? Will there be too much bounce on the 2x4 joists at 5'2" span?

Thanks for your input.

Steven_b
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Old 06-24-2014, 10:16 AM   #2
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


I'm no expert, but 2x4's are way undersized to carry people. I wouldn't do it and I'm sure it's not legal.

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Old 06-24-2014, 10:57 AM   #3
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


2x8 joists and rails 4x4 columns
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Old 06-24-2014, 11:49 AM   #4
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


mikegp, thanks for the feedback. I have double checked that a 2x4 joist at 5'2" is structurally sound and most charts indicate it is, but I too worry about the strength. I was hoping someone could give me their experience and give me the okay!

gmaint, why do you recommend 2x8 joists for such a small span? Would be great to get some more information. As I mentioned the underneath clearance is important, so the difference between a 2x8 and a 2x6 is important.

Are there any other products I could use that would give me shallower floor?

Finally, I worry that an 11' span of double 2x8 is more of a problem than a 5' span of 2x6 (or 2x4 for that matter).

Thanks for the replies.
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Old 06-24-2014, 11:56 AM   #5
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


Double 2x8 may be too bouncy. You can always add third 2x8 and add to post too, before you glue and screw down the deck.
2x4 joists will work, make sure none is damaged or has free knots. Your plan don't need joist hangers, use a ledger and drill nail holes. If turns out bouncy, you can add more 2x4, try a 2x4 "strong back" on the bottom, or double the ply deck.
Keep looking for span-load charts that you can make sense of. Dead load means the weight of the materials only. Live load means people, furniture, whatever that comes after. Chart combinations exist that you can use with your materials.
You have to read the fine prints. Sometimes one chart directs you to another or show what changes can be made.
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Old 06-24-2014, 12:02 PM   #6
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


"use a ledger and drill nail holes"
This is bad advice.You need the joist hangers attached to a firm ledger board.I don't even know what "drill nail holes" inplies?
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Old 06-24-2014, 01:34 PM   #7
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


Quote:
Originally Posted by mako1 View Post
"use a ledger and drill nail holes"
This is bad advice.You need the joist hangers attached to a firm ledger board.I don't even know what "drill nail holes" inplies?
Mako1, I agree. I suspect he means a ledger board with joists sitting *on* it, with nail holes drilled for toe-nailing the joist into it?

For the ten or twelve joists I will put my money into hangers and a strongly-fastened ledger board. I am building a 24" desk with triangular supports along the long wall that will be supported by the ledger, indirectly, as well, so I want it to be strong.

I am getting conflicting information about the 2x4 12" oc at 5'2" being rigid enough. I have some scraps I could mock it up and try it, I guess.

As for triple 2x8 does the extra depth give me much more stiffness or just avoid roll?

Would an engineered 4x8 be any better at avoiding deflection or is the 11' span simply too far for x8 dimensions?

Thanks for the feedback so far folks.

S

Last edited by steven_b; 06-24-2014 at 01:58 PM.
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Old 06-24-2014, 03:04 PM   #8
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


Steven,
I advised 2x8 primarily because I tend to overengineer things like that. Don't know how much weight you are planning to put up there, but Ibelieve you also stated that you are going to put a small desk up there (may have mis-read it). But that is just my opinion for what it is worth. Have you checked with local building department?
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Old 06-24-2014, 05:13 PM   #9
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


Quote:
Originally Posted by steven_b View Post

I am getting conflicting information about the 2x4 12" oc at 5'2" being rigid enough.



For an 'average' grade of timber, that would be stiff enough, particularly if you could glue the boarding down to make it act compositely with the joists.

Last edited by tony.g; 06-24-2014 at 05:13 PM. Reason: spelling
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Old 06-24-2014, 06:33 PM   #10
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


If someone asked me to under build something like that no mater how much money they offered I'd refuse to do the job.
Even that depth with a desk and three people walking around gives me goose bumps.
Is it really worth risking peoples lives to gain a few inches?
I've seen many a 6' porch or deck built with even 2 X 6's sagging and bouncing.
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Old 06-24-2014, 07:10 PM   #11
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


Quote:
Originally Posted by joecaption View Post
If someone asked me to under build something like that no mater how much money they offered I'd refuse to do the job.
Even that depth with a desk and three people walking around gives me goose bumps.
Is it really worth risking peoples lives to gain a few inches?
I've seen many a 6' porch or deck built with even 2 X 6's sagging and bouncing.
Joecaption,

What dimensions would make you comfortable?

Is it the beam length or the 2x6 joists?

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Old 06-24-2014, 07:28 PM   #12
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


If it was my job it would be 6 X 6's not 4 X 4's. (4x4's are going to twist and bow as they dry)
Notching the 6 X 6 for one of the rim joist so it's fully supported and through bolting it and the second rim joist.
2 X 8 rim joist.
At least 2 X 6 floor joist with joist hangers and no predrilling, just use joist hanger nails.
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Old 06-24-2014, 08:07 PM   #13
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


Quote:
Originally Posted by joecaption View Post
If it was my job it would be 6 X 6's not 4 X 4's. (4x4's are going to twist and bow as they dry)
Notching the 6 X 6 for one of the rim joist so it's fully supported and through bolting it and the second rim joist.
2 X 8 rim joist.
At least 2 X 6 floor joist with joist hangers and no predrilling, just use joist hanger nails.
joecaption - sounds reasonable to me, thanks for the suggestion. Is this how you would do it?
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Old 06-24-2014, 08:16 PM   #14
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


If it was my house, I would confirm the material requirements with a chart, and having found none, pay for a engineer.
But here is one experience. Years ago, we built 16' platform with single 2x4 on each side and 1/2" ply for nailing the siding. I was in sweats first time with the lead carpenter making it bouncier. My parents flat roof is decked with t&g 2x6 on flat and sitting on 4x14 beams 6' apart.. Used to have built up tar roof (was about 2" thick) with gravel on top.
I'm just saying don't underestimate 2x4.
Your deck is also indoors. If hangers make you happy, I'm happy too. You can also adjust for 2x different widths. I just don't think expense of hangers is necessary. Drilling is so you don't split the ends. Small job, you can afford the time for extra details.
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Old 06-25-2014, 01:47 PM   #15
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Can I build 11' x 5.5' loft with 2x2x8 beam and 2x4 joist?


Much as I would usually agree with joe.c's opinions on construction details, in this instance I believe it would be possible to prove by calculation that 2x4s @12" centres over a span of 62" would be OK in terms of bending stress and deflection.

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