Post and beams or long LVL joists
Hello All,
Met with my foundation guy today and the SE he uses. In a portion of the ground floor we want to remove a bearing wall to free up some floor space for a shop. Right now the bearing wall supports midspan 2by10’s at 16″oc that are 19′ long. So now the 2by10’s have a span of ~9.5′. This is the middle floor of a 3-story house.
I was thinking of lally columns and beams to open up the space reasonably. Becuase the foundation does this weird discontinous thing I was thinking seperate columns and beams for each section. Not a completely clear floor but way better than 2by6 joists at 16″OC.
My contractor and the engineer agreed that the easiest-cheapest-most elegant solution would be to sister LVL joists to the existing joists and clear span the 19′ with no midspan support. I like this idea because I get major open floor space for the metal shop. My contractor thinks it will be a wash moneywise as we will need about 20 LVL’s (exact size to still be determined by the SE) but we won’t have to but in the midbearing foundation in this case-well it wouldn’t be a foundation but pads for the columns-plus the actual columns-posts.
Here’s a pic of the bottom floor plan.
I want to clear span the area from the fireplace chase forward thru bedroom 1 the bath and the part of the garage wall. Yea I know it says inches but those are feet.
Daniel Neuman
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
Edited 4/16/2007 7:50 pm by madmadscientist
Replies
I am sure that your SE will figure out all the structural needs but my concern would be the loads on the floor from above. If the walls you are removing are load bearing it might be best to use beams and posts or you're lvl's may have to be big and expensive.
Yea I don't doubht that the SE can get it figured out....I was just wondering about whether or not money and time wise people thought the big LVL solution was best.
Daniel Neuman
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
Daniel,Can you raise the building's roof to compensate for the deep LVL's, or will the metal shop lose headroom? To keep from being bouncy, you will want 18+" joists, which is 9" of potential lost headroom. Smaller ones will hold the loads, but could be bouncy.The partition walls may help to damp out any bounce you experience with smaller LVL's.Bill
Hi Bill,
This is the bottom floor of a 3 story house so no I don't think raising the rest of the place to compensate would work. But we can dig down further to get the hoped for 8' finished height.
Unless you mean that once the place is up on cribbing that they remove the lower perimeter wall completely put in the deeper joists and then rebuild the wall slightly shorter?
Daniel Neuman
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
Sorry, I was thinking new construction. You can go deeper without going beneath the footings? Or is the place getting a new foundation...time to carefully reread your original post.If the LVL's will hold the loads and you can lower the floor in the shop basement, then it seems worth doing to avoid the dreaded posts. A few stout posts will carry more load than a $$$-load of LVL's over the long haul, so I'd do the posts if the shop layout would not be ruined by it.Bill
Sorry, I was thinking new construction. You can go deeper without going beneath the footings? Or is the place getting a new foundation...time to carefully reread your original post.If the LVL's will hold the loads and you can lower the floor in the shop basement, then it seems worth doing to avoid the dreaded posts. A few stout posts will carry more load than a $$$-load of LVL's over the long haul, so I'd do the posts if the shop layout would not be ruined by it.
Yep whole new foundation and slab for the entire house. My initial inclination is the same that the 4 posts plus the two beams would carry the load easier and cheaper but my contractor and the engineer were of the opposite opinion. The contractor I'm using is a good guy and he will do which ever way pencils out the most sane.
Daniel Neuman
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
I've looked a bit online but can not find a span table or span calculator for engineered wood. If someone could point me to one I would greatly appreciate it.
Daniel Neuman
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
http://www.ilevel.com/literature/TJ-9000.pdf
Hi and thanks for that post. I've read the section on floor joists and it looks like it says that the 9 1/2" deep by 13/4" wide 1.9E LVL will span the 20'. Though I am not sure that I am reading that right. I think it says that that is for L/360 which for a 20' run would be .66" which does not sound like what I would consider a strong floor.
The specs from the table are total load of 54 plf, a live load for L/360 of 42plf. That doesn't sound super strong-stiff to me (if I am understanding the table) It looks like I would have to go up in depth tp 11 1/4" which would give me a total load of 100 plf and a live load for l/360 of 70 plf. Alt I could go up in thickness of the beam to 3 1/2 by 9 1/2 for a total load of 119 plf and a L/360 of 85 plf.
But wow sistering up 20 3 1/2 by 9 1/2 beams sound like it might be a bit pricy...
Daniel Neuman
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
Edited 4/20/2007 1:41 am by madmadscientist
Daniel, ignore the L/360. You want the section with L/480. I haven't read all of the page I linked to but I assume it's there.
Also, if you haven't yet, you might want to check out Boss Hog's thread on vibration in floors. The gist of it is, the higher you make your joists, the less vibration you'll have, and that vibration is independent of deflection. IIRC.
The house I am building has I-joists 14" x 3 1/2" at 16" o.c., spanning 20' and 22'. Deflection is minimal, but there is some vibration. Maybe once the finish floors go down it will be eliminated.
I just checked the pdf doc--you're right in how you read the table. 42lbs live load is enough (40lbs is standard for living space) but it is for L/360 deflection, which means that over 20' it will eventually sag/bounce 5/8". Not terrible but not great either.
For deflection of L/480 you multiply the live load value by .75, which gives you an allowable live load of 31.5 which is barely enough for bedrooms and not acceptable for living space.
If you sistered both sides of your joists with LVL's you could use the 3 1/2" table which gives you an allowable live load of around 80 lbs, adjusted to 60 lbs for L/480 deflection. That is what you would want. That's a lot of wood!
By my reading if I used a single 3.5 by 9.5" 1.9E LVL beam I would get a L/480 of 63.75 plf add that to the existing beam strength and that seems like it would be a pretty strong -stiff floor.
That said, sistering up ~20 3.5 by 9.5" LVL's seems like the hard way round for me. The posts-beams wouldn't give a clear span but it does seem like it would be the cheapest-easiest way to go. This seems to confirm my original gut feeling that the clear spanning with the LVL's is possible but probably not the most money-time efficent way to go.
Daniel Neuman
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
Daniel, you say this is the last house you do, those posts are going to be there forever.
On the other hand, I had a shop with 2 posts. They were covered with extension cords, air lines & outlets.
Fire extinguishers too, handy central location for everything.
But still in the way.
Joe H
It looks like I would have to go up in depth tp 11 1/4" which would give me a total load of 100 plf and a live load for l/360 of 70 plf.
A 10K1 bar joist at 20' carries 199plf total, 97plf live (1/360). 10" tall, 100lbs ea.
12K1 at 20' is 241plf total, 142plf live, 100 lbs ea.
Spans are better than posts.PAHS Designer/Builder- Bury it!
Would this be a 19' clear span with no walls above on the third floor?
Hi Joe,
I'm sure I'm not being clear. The pic above is for the bottom floor of the house which is slab slightly below grade. Then the 2by10's we are talking about form the floor for the second floor of the house. Above that there is a third, lets call it, 3/4 floor which is a finished attic.
These 2by10's now only span 9'ish because of the center bearing wall. The engineer thinks we can span the entire 19' holding up two floors by sistering lvl joists onto the existing 2by10's....that's what I'm curious about...
Daniel Neuman
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
Daniel, I'm still a little confused by your drawing/description. What you've shown is the first floor, correct? (American meaning of first floor, or main level, usually just above grade.) With another story and a half above that? And the area for your metal shop is the basement? Sorry I'm just a little confused.
How is the headroom in the basement now? You could support the center of the joists with a steel beam (26.87' long). Might be 12" to 16" high though.
Sorry I am probably using some terms interchangably and screwing things up.
The level shown is the first floor which is a foot below grade. I should not be calling it a basement but in CA people get a little sloppy with that term. The shop area is on the first floor in the diagram above it would take over the areas listed as, living room, bathroom, and bedroom #1. Then yes there is a full floor and a half above the level shown.
Daniel Neuman
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer