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Old 04-03-2010, 03:21 PM   #1
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Cantilever Question


We are extending the width of a room on the top (second) floor of our home. The design calls for a 2' overhang (cantilever) over the first floor. The joists will be made of 2x10s and the wall studs will be made of 2x6s. The 2x10's joists will be 7' long (maybe an inch or two shy of 7' actually) -- 2' overhang & about 4' 10" in. So the cantilever ratio will be about 2.4 x 1. The local code does not address cantilevers. Is 2.4 x 1 structurally sound? I have read some places that it should be 3x1 and other places 2x1.

The foundation of the home is cinder block and in good condition.


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Old 04-03-2010, 05:01 PM   #2
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Cantilever Question


I can't quote you chapter and verse on this, but I have always understood it to be a minimum of 3:1.

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Old 04-03-2010, 05:05 PM   #3
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Cantilever Question


what he said is minimum
I have also put the crown of the joist down vs up as it will flatten out as you load it
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Old 04-03-2010, 06:13 PM   #4
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Cantilever Question


not sure about actual code here, but I would go 3:1 instead of 1/3'rds as per above.
max 24 " on the cantilever.
follow crown instructions above and install an upside down joist hanger on the inside end.
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Old 04-03-2010, 06:32 PM   #5
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Originally Posted by ivanl3 View Post
The local code does not address cantilevers. Is 2.4 x 1 structurally sound? I have read some places that it should be 3x1 and other places 2x1
Where are you located ?
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Old 04-03-2010, 11:07 PM   #6
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Cantilever Question


Pennsylvania.


Again, remember that I will have close to 5' depth and 2 foot overhang. The contractor ensures that this is structurally sound, even overkill in his opinion, but some of the previous answers indicate it should be 6' depth (which I cannot do). I would have to shorten the over hang to 1'8" to meet the 3:1 requirement.

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Old 04-04-2010, 08:39 PM   #7
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Cantilever Question


If it's anything like decks.......... " Floor Overhangs: Cantilevers of up to 3 feet are permitted with a backspan to cantilever ration of 2:1. For example: a 3 foot cantilever requires a minimum 6 foot joist back span. Connections capable of resisting the uplift forces at the backspan support shall be provided. A full depth rim joist shall be provided at the cantilevered ends of the joists. IRC R502.2.1" From: http://www.twp.cranberry.pa.us/Docum...w.aspx?DID=679

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Old 04-05-2010, 01:29 AM   #8
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Cantilever Question


Quote:
Originally Posted by GBR in WA View Post
If it's anything like decks...
but a deck would not likely have a wall and roof to support on the end of the cantilever...

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