Rafter Cantilever

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Posted by: from Belleville
7/3/2013 at 5:31:39 PM

What is the cantilever ratio for a 2x8 rafter?

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Date/Time7/3/2013 at 7:03:57 PM

Are we talking about a rafter or a truss? Or floor joist?

Need a lot more info on this one to be able to answer.

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Josh in Belleville
Date/Time7/3/2013 at 7:26:03 PM

It is a 2x8 rafter for a deck roof hanging from a ledger board against the house sitting on a 3 ply 2x10 beam that is 12 feet away from the house.

I need to know the maximum over hang allowed.

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Date/Time7/3/2013 at 7:31:16 PM

If you are talking about a structural member, like a floor joist. The general rule is 1/3 of the length unsupported, although a 1/4 the length is better. This also assumes that it is installed and tied into the existing structure properly.

As far as the building code, it will depend on the situation and there are limits. For actual roof rafters, they usually overhang any were from 12" - 48" and the 1/3 rule should be fine.

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Josh in Belleville
Date/Time7/3/2013 at 7:40:37 PM

Right now it has a 32" over hang with is better than a 1/4 ratio and the inspector is saying it might not be up to code but he gives no definite answer.

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Date/Time7/3/2013 at 7:56:15 PM

Your inspector is suppose to know that!!!! Every city has its own rules when it comes to decks, so I wouldn't be able to give you a definite answer.

A 32" overhang over a 12' distance should be fine, but it has to be attached to the ledger board properly. Maybe that is what he is questioning.

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Josh in Belleville
Date/Time7/3/2013 at 8:04:08 PM

I'm a framer by trade and this guy is an idiot but he has requested the rafters get hangers to the house and said to check if the overhang meets code so was looking for more info since I've never had this problem before.

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Date/Time7/4/2013 at 10:13:33 AM

it will be 1:4

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Date/Time7/7/2013 at 9:34:07 AM

The roof rafter has to be connected to the ledger board with hangers (use structural fastners) and the 1:4 rule would suffice.



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