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Old 10-16-2012, 12:53 PM   #16
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Hanging a beam in the attic for joist support


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Originally Posted by abjkkc View Post
I am by no means an expert, but going through a pretty similar situation as you. You can see my thread over at:
Load bearing wall removal

My situation is compounded by the fact that I'm not putting my beam over the joist splice, but otherwise very similar. My house width is 25', while yours is 20', my beam length is 11', while yours is 10'. I went to the local Lumber yard and they sized an LVL beam of 2 - 9 1/2" LVL's, 11' long. He said that if I didn't want to use LVL, I'd have to use 3 - 2 x 12's, so be careful about your beam size. If you have a Lumber yard close, use them! The guys who post regularly here know their stuff, and while they won't size the beam for you, their advice about getting a professional to help in sizing the beam is right on. Like you, the only thing above my joists is insulation and a roof, but this is still a really big deal.

I'm planning on using Simpson THA-218 hangers on mine (this is what was recommended by the lumber yard). You can see them here (http://www.strongtie.com/products/co...s/tha-thac.asp), although if you're going directly over the splice, you may need the THA-218-2 (don't get the THA-418 - the joist hanger width is 3 5/8" which is for supporing an LVL. The 218-2 is 3 1/8" wide, so 2 - 2x joists will fit in it perfectly.
You'll have to cut holes in the ceiling to pass the hangers up through so the joist fits in the saddle.

Like I said, I'm certainly no expert, but my project has been approved by the local building inspector, and I just though my situation might help.

Good Luck!
Great info - there is a lumber yard near by, I'll go and have a chat with them and see what they have to say.

My only fear with using the joist hangers that you mentioned is that I would have to cut the lath at each joist. The lath runs at 90 to the joists so this would leave these few strips of lath completely unsecured from the joists. Not sure if it matters, it may hold with just the plaster securing it but it makes me nervous.

The only experience I have with lath/plaster is knocking down a ceiling to help my parents with their renovation and I seem to remember kicking down from behind would cause a HUGE portion to fall.

I took a brief look at your thread and it looks like a lot of good info - I'll have a read through it tonight.

Thanks
-T

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Old 10-16-2012, 01:24 PM   #17
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Hanging a beam in the attic for joist support


tarnishd; here are some figures for you to put the beam size in perspective.

If your beam is spanning 10ft, and the width of the room is 20ft, then about 100 sq ft of ceiling will be supported by the beam.
We then need to work out the total load the beam will be carrying and this is split into two components - dead load and live load.
The DEAD load is the weight of the structure itelf; typically, the dead load of a ceiling is around 10 psf. The LIVE load is the weight of things you might store in the loft space. Your local code will specify this but it should be around 20 psf.
Therefore the total load your beam will carry will be 100 x (10+20) = 3000 lb (excluding the weight of the beam itself).
Knowing the total load, the span, and the cross-sectional size of the beam, it is possible to work out the maximum bending stress in the timber. Without going into the figures here, the maximum stress in your beam will be just shy of 1000 lb/sq.in.
I would say that is borderline for mot commonly-available timbers, so I would consider upgrading to three 2x10s to be on the safe side.

(if you are not bothered about a permit, you wouldn't need to take account of any live load and the two 2xs would do).
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Old 10-16-2012, 01:33 PM   #18
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Hanging a beam in the attic for joist support


this link will provide you with the Prescriptive Girder and Header Spans based upon the 2009 International Residential Code.
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Old 10-16-2012, 01:40 PM   #19
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Hanging a beam in the attic for joist support


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this link will provide you with the Prescriptive Girder and Header Spans based upon the 2009 International Residential Code.
Wow that's a great resource! So supposing my 20ft house width, ~10ft span it looks like

3-210 with one jack post

I just noticed this is for an exterior bearing wall... so for an interior bearing wall it would actually be,

4-210 with one jack post

but this is for supporting 1 floor. Is the attic considered a floor?

Last edited by tarnishd; 10-16-2012 at 01:44 PM. Reason: referred to wrong table possibly
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Old 10-16-2012, 01:52 PM   #20
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Hanging a beam in the attic for joist support


do you have a scuttle (small opening), pull down stairs or fixed stairs to access your attic?

scuttle and pull down stairs the code requires 20 pounds per square foot live load (as tonyg said 10 psf dead load typical)

if fixed stairs then 30 psf live load
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Old 10-16-2012, 01:53 PM   #21
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Hanging a beam in the attic for joist support


this is based upon the building code in the states, not the Canadian National Building Code (not sure what their requirements are).

if you like, have a look http://www.e-laws.gov.on.ca/html/reg...s_060350_e.htm
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Old 10-16-2012, 01:57 PM   #22
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Hanging a beam in the attic for joist support


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do you have a scuttle (small opening), pull down stairs or fixed stairs to access your attic?

scuttle and pull down stairs the code requires 20 pounds per square foot live load (as tonyg said 10 psf dead load typical)

if fixed stairs then 30 psf live load
Definitely scuttle, it's one small opening in a closet that I can barely squeeze through.
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Old 10-16-2012, 02:42 PM   #23
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Hanging a beam in the attic for joist support


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scuttle and pull down stairs the code requires 20 pounds per square foot live load (as tonyg said 10 psf dead load typical)
(See! I'm learning US code live load requirements!)

Last edited by tony.g; 10-16-2012 at 03:42 PM. Reason: spellyng
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Old 10-16-2012, 03:09 PM   #24
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Hanging a beam in the attic for joist support


that you are!

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