I am trying to figure out a way to open up the basement in my side-by-side duplex. The building is about 30′ wide and the floor is supported by 10′ joists spanning 1/3rd of the building width supported with post and beams. I want to remove the post and beam and support the floor above with a center load bearing demising wall.
Are there any techniques or hardware that could provide a connection at the joist splice that could make the joist strong enough to span the 15′ to the center wall without a post and beam support under the splice?
I want to avoid having to put in a new, sistered 15′ joist if at all possible.
Thanks!
Replies
Someone with a lot more knowledge than me will probably come along shortly and do all the calculations and load diagrams, but the short answer is NO!
The reason for the support is to carry the splice. You couldn't put enough nails in the splice that would stiffen it up enough to carry any signifigant load without eventual failure. To eliminate the post/beam setup and span the entire distance, you would need to sister/replace the existing joists with either dimensional lumber (but this span pretty much maxes out 2x10 SYP) or an engineered product.
What you use also depends on what is above. Does the post/beam support more than just the joist splice, or does it also carry a load from walls above? Is there tile on the floor above that needs extra stiffness? Is there a pool table/grand piano on the floor above.
It's not a simple question, so it's hard to give a simple answer.
Are you trying to have a room down there?
Yes, trying to expand the habitable space to the downstairs (it's actually more like an above ground basement).
The joists are supporting the floor above and the roof only. The only bearing wall on the second floor is located in the center (directly above the new load bearing demising wall).
I attached a rough sketch that might clarify.
Thanks for the help!
OK, hear is how I would do this. I would support the joists either side of the splice, and then cut them back and install a beam up in the floor.
I'm a bit unclear about what's staying and what's going in your picture.
I was also a bit unclear about "demising wall" until I read this article
You'll end up adding new 15' joists. The old joists were sized for a shorter span, not to mention it's not possible to splice in new joists to the end of the old.
You might be able to do steel beams to replace many of the posts.
Beer was created so carpenters wouldn't rule the world.
You probably have many more issues than just sistering or replacing joists. You will need footings under this new "demising wall" whatever that is, and you will need to have studied out the load transfers from above that currently land over these existing support systems.
What you 'want' may easily turn into completely restructuring the whole building and you need a structural engineer on site to plan it out for you. Failure to do it right could mean having the whole thing fall in around your ears - literally! Short of total collapse, you are likely to have ruined the structure by creating sags, dips, and cracks everywhere.
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You have such a way with words.
Sadly for the OP you are quite correct.
I was hoping someone would say that.
A DEMISING wall, as I understand it, is a wall that separates different occupancies. I had the same reaction the first time I ran across/ heard the term. It is often a fire rated wall. I first ran into it doing some finish out in a commercial building with multiple tenants. I have yet find it in any standard, architectural, or construction dictionary. The spellcheck did not kick it out so I guess it is a word.
The closest thing that I have found is DEMISE as a law term "The conveyance of an estated, chiefly by lease." Or, I guess, as in the leasing of a space in a building.
Edited 12/1/2008 11:20 pm ET by oops
The closest thing that I have found is DEMISE as a law term "The conveyance of an estated, chiefly by lease." Or, I guess, as in the leasing of a space in a building.
Makes sense, demissum in Latin is to set or lower down; the adjverb demisse means low to the ground--both suggest the way in which defining lines might be set upon the ground or foundation of a thing.
In english, "demise" is used as a synonym for "dead," but that is probably a transference from "meeting one's end or limit."
In TI work, the demise is always the limit where the Leasee's rights end (and usually where the contracror's get all fuzzy, as it is often the center of a wall, worse still, a partition).
It's very common that an AHJ will have a legal definition on how demising walls must be built. This can vex those who fail to look up those definitions. Like a local builder who wanted a common ground floor under three sepeate townhomes. Oops. falied to make the floor--a resulting demising surface--fire rated. Looks embarassing in sticks, on hold.
Occupational hazard of my occupation not being around (sorry Bubba)
Finally, some sense out of it all! ThanksNever heard the term before and thought it was a mis-spelling of dimensioned or something...;)
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I'm surprised you were not familiar with demising wall. But then I have been on the commercial side for 20+ years and it's probably not used at all in single family work. back when you worked apartments in Colorado, I wonder if they would have used the term then. Probably not, although a fire wall between units might be considered a demising wall."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Would there be a difference between a firewall and a demising wall?
Never heard of demising either 'til now. Never know what you're gonna learn around here.
Yes.(as I understand it) A demising wall/partition is specifically a legal separation between two spaces/leases/ownership. If however it also separates two different occupancies that have different classifications such as a daycare facility from a lets say a paint store, it may also be a fire rated wall/partition. It also may be fire rated wall/partition that simply reduces the sizes of an area as set forth in a building code or some zoning requirement.
In my limited experience, I have found that contractors use the term pretty loosely to describe any wall/partition between two spaces.
On those jobs, I did the backup framing and exterior trim/siding packages, so I rarely saw a set of plans
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"About looking up those definitions" As I stated, I have not been able to find a definition of the term. I could not find it in the either the International Residential Code or the International (commercial) Building Code. I even went back and looked in my old Real Estate Law books and could not find it there.
And now to further show my ignorance, what the heck does "AHJ" stand for? I see it use here all the time, and assume it has to deal with the powers that be, but it's not something I am similar with.
Too the original poster, my apology for horning in and changing the subject. May I just suggest that you listen very carefully to what Piffin said.
AHJ = Authority Having Jurisdiction
ETA: Thanks for the description.
Edited 12/2/2008 1:40 pm ET by john7g