Advice on Repair to Modified Main Beam in Bi-Level House
Bernie_01
| Posted in Construction Techniques on
Hello. I’ve got this repair to make but have some questions. I’ve had lots of experience with light to medium home repairs (re-framing/hanging new doors, lots of drywall, trim, finishing work, etc.) but this task is at a higher level than I’ve dealt with in the past. Please forgive my occasional lack of correct terminology.
Background: Purchased a bi-level home last year, built in early 70s. We and our inspector missed some significant floor sag in a section of the house where the kitchen, dining room, and living room meet on the main (upstairs) level. I removed the downstairs ceiling drywall under the area to see if I could identify the issue and it became clear right away what was going on. At some point, someone cut and moved this section of main beam flush. In doing so, they added another 2×10 to the new beam section and had it sit on top of the ends of the original beam on each end of the span between the two columns. So you have 4-ply 2x10s resting on each end over the existing 3-ply 2×10 main beam. However, they failed to properly fasten the 2 by’s in the new, flush beam together so they are pulling apart and sagging. Even WORSE though is that they didn’t use joist hangers to attach the floor joists to this beam. The are only toe-nailed into the flush beam plus with a big notch cut out of the joists to sit on a horrible, strip of 2-by nailer (~1.5″ x 1.5″). NO joist hangers used, either side of the new beam! This joist-nailer combo is also pulling apart and sagging.
I’ve spoken to an engineer and the plan is to temporarily support the joists with temporary walls using jack-posts, slowly raise the ceiling/floor joists to proper height plus enough wiggle room to get the new beam in, remove the bad beam, replace it with a 3-ply lvl, and put in all new joists over their full span, along this length of beam, so that they can be properly attached with hangers on the new beam (since the existing joists are cut back, notched, and not long enough to meet the new beam once installed).
I have two main questions:
1) The LVL beam is 9.5″ high while the original 2×10 beam would have a nominal height of 9.25″ high. I had concerns re: the extra quarter inch of height in the new LVL beam and don’t want to replace my sag with a ridge. In measuring the existing beam though, both the original and the moved flush section, they are both measuring closer to 9″ even anyway. So, in theory, the extra height of the new LVL would appear to exactly make up for some “squash” in the height of the original beams, making the extra little height a wash. Am I safe in putting in the LVL at it’s standard height or do I need to do more analysis here, do something different?
2) I was assuming I’d “sister” the new joists by putting them directly alongside the old ones. (“Sister” in quotes as I may be deviating from the true definition of sister.) The old ones would end a couple inches short of the new beam wile the new joists would be properly hung on the new beam. Since the old joists would no longer be supported at the beam end, I assume best thing would be to glue and nail the old joists to the new. I just wasn’t sure if the weight of the old joist would be a drag on the new one, adding unnecessary weight to that new joist and beam. Not sure if there is even an alternative though. Completely remove old joists after new ones installed? There are hardwood floors on the main floor above so don’t know if removing the old joists would cause issues there.
Thanks to anyone who took the time to read this. I can add pictures as a follow-up if that helps.
Thank you,
Bernie
Replies
As an addendum, I actually was digging around more and do now see there is a Microlam option which is the exact 9 1/4" height. I had been looking at the VERSA-LAM options which have a 9 1/2" height. The versa-lam seems to be more available in my area but I can see about the microlam. Still kind of wondering though if the extra 1/2" of height could be a good thing in terms of making up for what appears to be some "squash" loss of height in the original beam.
You are correct with the term of sistering. I would do as you are planning, might as well use the existing floor joists that are there instead of throwing in a dumpster. Also, more wood typically means more strength. If you remove the old joists it will definitely mess with the subfloor which in turn will effect the finish floor. The LAM will not shrink or squash like a 2x10. The new 2x10’s will shrink some, so I like to keep those a little higher than the beam. A steel flitch beam might be a good option as well, but confirm w/ your engineer. The engineer will need to sign off on whatever you decide to do.