[Tonkadad]

I checked out a small drywall job the other day and noticed the 2nd floor was sagging. Basically its a diningroom that cantilevers approx 8' past a solid wood beam. The room is about 10' wide and 16' long. The joists are perpendicular to
the wood beam.

The drop at the end of the joists is about 2". The joists are 2" x 10" @ 16" o.c. At the point where the joists are supported by the wood beam, the floor has a hump. The house is about 30 years old, the current owner has been in it less then 2 years.

A couple of framing books I have state that cantilever joists, when they are carrying load bearing walls (in this case an exterior wall and roof) cannot cantilever out more than the depth of the joists.

Does anybody know if this is the case or is it more complicated than that.

thanks for any input,

Bruce

 

[Bjd]

I not real sure but I though that you could not extend more than 1/3 the total length of the floor joists.
That would mean that your 2 x 10 would have to be 24ft long, with 8 feet sticking out for the canterlever.
Thats a long piece of wood, and at 16' in length that quite a bit of wood.

BJD

 

[K2]

The cantilever should be engineered for live loads, dead loads, snow loads,species of lumber,and probably a bunch of other considerations. The cantilever can be increased by using 12 in. centers, microlams, steel, and or other materials. I framed for 20 years using the Universal Building Code and the spans you are talking about are not even close to acceptable for that code. Obviously reality shows them not being acceptable with the bending you're describing. A fairly simple solution for you homeowner might be some post and beam out at the end of the cantilever, or close to the end. I would suggest to them having it engineered. I personaly would not do any work on the house until it was corrected because of liability. Bending problems generally only get worse.<P>
According the the codes I worked under there is never a set rule for figureing cantilevers. Got to plug the info into the formulas and get your answer. I had some minimal experience with the math years ago but since we had to have an engineers stamp on everything I let them do the math.Rob53

 

[Glasshousebltr]

Single story, 2x10, with roof load stops at 24", no good framer will canterlever past here and most advise against more than 18".

Two story stops at 16".

Just rules of thumb.

Bob

 

[K2]

I believe glass's rule of thumb would work well in anybodys calculator. Eccentric and point loads should also be a consideration on a cantilever. A large door opening can put an extra load on the unsupported rim joist. An upper floor opening transferring to the lower floor door opening can put a substantial load on the rim. Any problems with these scenerios, however, would probably not be as pronounced as the problem from the original post but just something to consider. RT<P>
I think I need to get a job.

 

[PipeGuy]

T I personaly would not do any work on the house until it was corrected because of liability.

Amen. :Thumbs:

 

[Tonkadad]

Recover lost ground or just stop the bleeding?

If they decide to go with a beam and posts near the end of the joists, would it make sense to just stop any more drop or to slowly gain back some lost ground by raising it a 1/4" every couple of days to try and relieve the stress in the joists.

Obviously I am not an engineer nor pretending to be one. More so looking at this as a mental exercise "how to solve this problem".

I have already reccomended they get an engineer to look at it.

thanks for all of the replys.

regards,

Bruce

 

[Glasshousebltr]

If it's only 30 years old, raise it. The 70s were the years of massive platform framing and cutting back to pine and spruse, she'll take a hell of a lift.

Watch your cornis and do it day by day a little at time and you can lift her to the jet stream.

Bob

Oh yea, keep your eye on any wires or plumbing also.