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bfackrell 01-28-2008 11:45 AM

2' Cantilever
 
1 Attachment(s)
I would like to add a 2’ cantilever to the back of my house but I have some concerns:


1- If I simply extend the existing floor out (probably 2x12 construction) will the new wall support my roof or will I need to install beams where the existing wall is?
2- Are there any problems associated with having no overhang?
3- How far into the existing floor joists should my new 2x12’s extend?

*Please see my attachment.

Thanks
Brad

concretemasonry 01-28-2008 12:37 PM

That is a lot of work for just an extra 2'.

What kind of a roof system (framed or truss) do you have?

You will have to tear into your old floor and sister some new joists as a minimum. This will also entail rerouting electrical and other utilities in the basement/crawl space.

Without an overhang, you will have to do some real planning to have adequate insulation over the 2' and to maintain ventilation of the attic area.

You will need an engineer to get a permit.

bfackrell 01-28-2008 12:53 PM

Quote:

Originally Posted by concretemasonry (Post 92872)
That is a lot of work for just an extra 2'

The house is very small, two feet will add a lot. :wink:

Quote:

Originally Posted by concretemasonry (Post 92827)
What kind of a roof system (framed or truss) do you have?

It's a house that I'm thinking about buying so I only took a quick glance into the attic and I believe it's framed construction. It's an older house and I don't remember seeing a lot of cross members.

How would framed or truss make a difference? Shouldn't the load always transfer straight down the wall?

PSHome 01-28-2008 03:28 PM

for every 1ft of cantilever you have to have 2ft sistered onto the existing joist so if you want 2 ft your total board length is going to be 6ft total
is the roof already cantilever out 2ft if not you are going to lose head room. unless you do some roof work

bfackrell 01-28-2008 03:33 PM

Thanks for the info.

Yes, the existing roof is already cantilevered. I'm just not sure if the new cantilevered floor will hold the weight of the roof.

PSHome 01-28-2008 03:40 PM

i would put a beam where the existing wall is so that the roof doesnt have to depend on that cantilever to hold the weight depending on size o course if its a little area maybe but if its the whole side of a house no.

oldfrt 01-28-2008 04:38 PM

Quote:

Originally Posted by PSHome (Post 92927)
for every 1ft of cantilever you have to have 2ft sistered onto the existing joist so if you want 2 ft your total board length is going to be 6ft total
is the roof already cantilever out 2ft if not you are going to lose head room. unless you do some roof work


I wouldn't use this equation,without getting someone to look at the actual home.
It doesn't sound right to me,definitely not with a weight bearing wall on it.

concretemasonry 01-28-2008 05:11 PM

Adding a beam 2' from the new outside wall will be ugly and chop up the interior because of the depth usually required.

If you have a trussed roof, you are asking for a disaster since the present roof is designed to bear on the walls where it is now. Changing the bearing location can easily cause a roof system failure.

You need professional help since it is not as simple as you think.

robertcdf 01-28-2008 08:21 PM

That wall can NOT support that weight without an engineer getting involved.


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