Author Topic: Maximum cantilevered overhang?  (Read 3166 times)

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Offline NM_Shooter

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Maximum cantilevered overhang?
« on: August 25, 2008, 07:53:13 AM »
I'm using two beams with floor joists on top in a cantilevered fashion. 

I'm curious as to what the maximum overhang would be using 16" spacing, and #2 grade for the following:

2X8
2X10
2X12

I know snow load plays an important role... any rule of thumb to be had for this?

Thanks,

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Offline lockman

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Re: Maximum cantilevered overhang?
« Reply #1 on: August 25, 2008, 11:03:38 AM »
I'm pretty sure the maximum cantilever for a load bearing wall is as long as the joist is high. For example, using 2x10 joists, you could cantilever them 9.25 inches out. For non load bearing, it would be 1/3 of the total joist length. I'm sure someone will be along shortly to correct me if I'm wrong or to get more specific.


Offline MountainDon

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Re: Maximum cantilevered overhang?
« Reply #3 on: August 25, 2008, 05:27:46 PM »
I believe the correct answer is "... depends."

There are cantilevers and then there are cantilevers.   ::)

As John originally drew the little house plans, 14 foot wide on 4x8 beams, he set the spacing of the beams to have 2'2" overhang measured from the center of the 4x8 beam. That's with 2x6 joists on 16" centers.

I have some snow load to deal with too but not as much as in the Chama area. I feel pretty comfy with my specs... 2x10 joists on 16" centers, total length 15'9", and 12" of overhang, no loft.

This one of those calculations for which there are no easy tables; at least I don't have them. An engineer would do load calcs for common materials, modulus of elesticity or something, etc. Then multipy that by his safety factor, etc.

Just because something has been done and has not failed, doesn’t mean it is good design.

If you didn't have the time or money to do it right in the first place, when will you get the time and money to fix it?

Offline soomb

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Re: Maximum cantilevered overhang?
« Reply #4 on: September 05, 2008, 09:23:01 PM »
is it "all bets are off" once you go above one story?  I like Willys cabin (Chewsaw) and I noticed his has the beams at the wall edge.  I was wondering if once you go above a single floor, if cantilever goes out the window if the cantilever is bearing the load for 1.5 or 2 stories.
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Offline glenn kangiser

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Re: Maximum cantilevered overhang?
« Reply #5 on: September 05, 2008, 10:24:11 PM »
Probably still down to calcs in reality, but it may be easier to add a middle beam and move the outer beams out than to pay an engineer to calc it-- John's two story plans are way cheaper than an engineer.

John used the cantilever to allow a wider span with smaller joists.  The cantilever provided added stiffness in the center, offsetting part of the load.
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