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Old 10-31-2012, 10:17 PM   #1
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Sizing trimjoist for 19' span


Hi, I have a masonry garage with a 18ft high ceiling and would like to add another level inside (a second floor, in other words). I'd like to use Trimjoists to do this and was wondering if I could get a sanity check on the depth I will need.

The width of the garage is 19'3" from brick to brick. I want to clear-span this. Looking at the span tables from trimjoist ( http://www.trimjoist.com/spans.html), it looks like I could use j-12's spaced 24" on center to get a L/465 floor with a load of 40-10-10.

Frankly, this sounds ridiculous to me. I made the mistake of spanning 20 feet before on another project with 12" trimjoists and spaced them 19.2" OC and have one hell of a bouncy floor.

So I was thinking of just bumping up to the J-14 and spacing at 19.2". According to their table, even with a 40-20-10 load and L/539 defelction, I should be able to span over 24' with this setup, and I only have to go a bit over 19'.

Does this sound like a good plan? Will it too be bouncy or is it overkill? Truthfully, I can't tell because those span tables look silly to me. Is there something I'm missing?

Also, most of the joists will go all the way across the 19' , but will be shorter where my stair well is. Should I still get the same depth of joist for that section for the uniformity of ceiling height in the space below, or should I save a bit of money and get smaller depth joists over that section?

Thanks in advance,

Cliff

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Old 10-31-2012, 10:36 PM   #2
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Sizing trimjoist for 19' span


you will probably need to get a few special trimjoist hangers with your order to work around the stair opening

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Old 10-31-2012, 10:38 PM   #3
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Sizing trimjoist for 19' span


Yeah, I'm looking at hangers right now. I see the specifications for a variety that I will need around the stair opening, but, distressingly, I don't see any masonry hangers that look like they will work if your masonry is already in place. There are several that look like they can be laid in while the wall is being built, but my walls are built already...

I don't really want to mount a ledger board all the way around.
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Old 11-02-2012, 09:19 AM   #4
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Sizing trimjoist for 19' span


I have decided, from talking to a few others, to go with 14" deep trimjoists spaced 19.2" OC.

Do you have any suggestions for the method of attachment? Trimjoist has a specifications guide for masonry connectors, but they are the type that would need to be placed as the wall is going up, in between courses. I don't see any that can just be bolted to the wall. I asked trimjoist about it and they told me I'd need to contact a company that makes fasteners.

I'm open to other options, like installing a steel ledge or a ledger board, but trimjoist won't spec ledger boards, so I'm not sure what to do here.
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Old 11-02-2012, 09:37 AM   #5
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Sizing trimjoist for 19' span


what will this level be used for?
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Old 11-02-2012, 11:01 AM   #6
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Sizing trimjoist for 19' span


Initially some light storage, but very soon a one bedroom apartment.
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Old 11-02-2012, 11:14 AM   #7
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Sizing trimjoist for 19' span


One way would be to build 2 X 6 walls along the outside walls so the ledgers would be fully supported from below.
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Old 11-02-2012, 11:16 AM   #8
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Sizing trimjoist for 19' span


not a bad idea, but I'm unsure about the slab and whether is enough footing underneath the section near the walls. I'd hate to transfer my load down there just to get a cracked slab abd wobbly floor. But it may be a good option.
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Old 11-02-2012, 11:56 AM   #9
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Sizing trimjoist for 19' span


if it was mine I'd do the joists at 16" o.c. if you are planning on an apartment above. less deflection in the subfloor is they put a heavy item that bears in between joists.

just a thought. like Joe's ideal of the wall to support the joists, will give you a place to run plumbing waste pipes down without showing in your garage, same with water lines
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Old 11-02-2012, 12:02 PM   #10
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Sizing trimjoist for 19' span


Thanks. Do you think a 2x4 wall would be enough? I know it's enough 'ledge' according to trimjoist...they only need 1.75" of bearing, supposedly. Of course, 2x4 is not as strong as a 2x6, but I'm trying to save a little width to make sure I can get two cars in there comfortably.
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Old 11-02-2012, 01:02 PM   #11
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Sizing trimjoist for 19' span


if the joists aline with the studs then the building code only requires a single top plate. you would only need walls on opposite sides to bear the joists. 2x4's are plenty strong to handle a single floor.

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