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cliffhan 01-22-2013 09:29 PM

Addition to load-bearing cantilever
I plan to add a sunroom attaching to backyard side of my house and try to use the existing wall to support the roof. The existing wall is oncantilever(~10") made with 2x10". is this fine or should I make extra support to the cantilever?

joecaption 01-22-2013 10:15 PM

Not sure how anyone would know with no location, no plans, no pictures, no drawings.

GBrackins 01-23-2013 07:50 PM

Welcome to the Forum!

certainly some photos would aid us in providing some useful comments. What is the depth of the cantilever? does the roof bear upon the cantilevered wall or is it a gable endwall? how is the sunroom to be constructed, roof type, cathedral ceiling, etc.? I could go on with more questions ...... many items have to be evaluated before a simple question can be answered.

what is your building code? do you construction drawings? are you required to file for a building permit? just a few more to think over

carpdad 01-23-2013 09:54 PM

If the cantilever is less or equal to 12", you can use it as load bearing structure. That assumes many things about spacing, point loads, roof material and shape, existing header in the wall, etc.

Easier would be to put a girder under the wall and incorporate it into the sun room. Follow the deck requirements but 24" footer to support the existing and new structures. 24" is probably an over kill, but you can get permit with a little over engineering and less fuss.

cliffhan 01-23-2013 11:04 PM

Thanks for all your responses. Sorry for not having any pictures nor drawing. I am at the very early concept planning.

to Gary, the depth of the cantilever is about 10 inches. Current roof is on the cantilever. The roof for the sunroom will be Skillion style. I'll do the drawing, permit after the major structure issues resolved. my house is a two stories, with backside of the first floor 3-4 feet into the ground. The cantilever is part of the floor of second story. The sunroom is going to be on the first floor with 3-4 feet into the ground. I want the roof of sunroom to be above the floor of the second story at the junction so that we can have more head room and sunlight.

By the way, I am in northern New Mexico. there is not much snow in recent years. I'll try to get some picture later.

I like the girder idea and will think it further.



GBrackins 01-23-2013 11:05 PM

from the 2009 International Residential Code, your local code may vary:

R502.3.3 Floor cantilevers. Floor cantilever spans shall not exceed the nominal depth of the wood floor joist. Floor cantilevers constructed in accordance with Table R502.3.3(1) shall be permitted when supporting a light-frame bearing wall and roof only. Floor cantilevers supporting an exterior balcony are permitted to be constructed in accordance with Table R502.3.3(2).


the cantilever must be able to support all imposed loads, both existing as well as the sunroom.

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