Strategies To Add Support To Cantilevered Living Space.

bob_cntrctr

Gentlemen,

Here's a fun one. This house sits on a concrete foundation with a small crawlspace. Interesting "design", the sun-room is exterior to the foundation. They simply extended the floor joists past the foundation to create a cantilevered room, extended about 6-feet past the foundation. Then they filled in between the joists under the sunroom with plywood to close in the "crawlspace". Under the sunroom is just wide open to the elements. It hangs there, about 6-inches off the ground, underside exposed, no insulation, no support.

Well now it's 60 years later. Incredibly, nothing has given out, yet. But the new owners think it might be a good thing to not wait until that point and want to add a support beam under the outer edge of the sunroom so it's not cantilevered anymore. Makes good sense, but this looks like a job where doing it wrong could make things a lot worse. Imagine two piers at either corner sunk too shallow to resist frost heave - disaster.

So I'm looking for suggestions. I'll try to attach a sketch of the situation.

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BattleRidge

I would insulate it then put some painted plywood on it. Whats wrong if the cantilever is done corrrectly?

canadianwood

I'd probably have a look at the other end of the joists (where they end it the house) and see it they're pushing up. Min ratio for non-load bearing (ie, roof load only) cantilever is 2:1, so for every 2' into the house you can project 1' out. However, max projection for 2x10 is 24", you are way beyond that (I'm assuming you are dealing with dimensional lumber, seeing as this was built 60 yrs ago ).

There are special cases requiring structural engineer stamping but we won't talk about Frank Lloyd Wright-ish projections on residential houses.

If homeowner wants to go through an expensive procedure for piece of mind then your only option is to excavate under it, by hand, until you reach a req'd depth (depends on frost line) and pour a footing. From there you can start your foundation

Alternatively, you can get friction-type piles directionally drilled on either side of the cantilever, finish them off flat and run posts and beam off that. I suspect that this may be more expensive though...
Here's my crappy 5 min picture:

Attached Images

sunroom.bmp (120.1 KB, 67 views)

bob_cntrctr

'Cause lookin' at it it just looks wrong. When two people walk around in it, it feels wrong. So I had a feeling it was not done correctly...and apparently:

Of course there's always

I was thinking maybe those two piers I mentioned, but to a full depth, and a beam. But wondered if there were any other bright ideas out there.

naptown CR

I agree with adding a beam and support posts at proper intervals ( you did not say how long the room was only the projection)_ Piers to below the frost line are adequate if footings are sized correctly. The biggest obstacle I can think of is the fact that this is only 6" off the ground this doesn't leave you with much room to install a beam unless you set it into the floor structure as a flush beam.

bob_cntrctr

It's 16-feet long.

Ya, I'm leaning that way. Flush - like it - I could take 6" off the end of the joists and lay in four 8-foot 2x10's, twice for the length, with piers at each end and in the middle where they meet, sunk below frost. Hey, that's not bad...

knucklehead

I had a similar situation on a house a while back. This was an engineer who had a 5' overhang that he designed 20 years ago to be suspended from the trusses. He thought the wall had seperated from the trusses . Once I took the siding off you could see that it had all sagged together. Anyway , we ended digging holes andpouring peirs by hand. We also bolted a flitch plate on the outside of the rim joist. I think the room was 14' wide. We put adjustable steel columns on the corners so he could raise it if he wanted to try to.
When those joists have been sagging for twenty years , they wont just bend right back. When we jacked up the corner the joist would lift off the foundation.
He just couldn't beleive that the trusses had sagged that much. One idea he had to fix it was run a steel diagonal back to the foundation , which would work ,but way too much digging under this overhang with maybe 2' of clearance

bob_cntrctr

Ya, that sounds very much like my situation, and very much like what I'm gonna do. A second look suggests there is sag here as well - the door to outside scrapes the floor when pulled wide open. So I'll put screw-jacks into the concrete piers for adjustment. Thanks.