I am in the process of remodeling a house built in the late 1930. I just noticed that the floor are sagging about 1 inch on a span of 16 feet. The joist are 2×6 sistered with a 2×4 with a span of around 9 feet. The floors above are oak floors that I would like to salvage. I have several alternatives : 1) Put a 10 inch LVL beam across the whole house in the middle of the span and raise the joist by 1 inch using jacks. 2) Tear the whole floor and sister a 2×6 LVL beam next to the other joist. 3) Put a 10 inch LVL beam across the whole house in the middle and leave the joist as is.
Any one have any ideas? Please advise.
Thanks for the help.
Replies
You need to do some calculations on the span that the LVL can support between posts, and decide if the posts can be located to not mess up the downstairs. "10" LVL beam" doesn't say enough: here are some span charts from Georgia Pacific to help you figure it out. Be careful about substituting one manufacturer's product for another's if you don't have GP products in your area.
If you raise the joists with the LVL, take out a strip of drywall or plaster where it will sit so you have a solid connection. Cracking will vary depending on whether its a diamond mesh lath and plaster ceiling (at the best) or drywall (at the worst).
Another truly "outside the box" option would be to slip new joists in from the outside, on the order of how afterthought, cantilevered balconies are made. You would have to support the floor from the interior to put it in plane, then cut openings to slide in some new joists to the other side, effectively halving the space between joists. If you have any wires traversing the ceiling joists, this won't fly.
If it were me--actually, i did this very thing--i would rip out the ceilings and sister in 2x10's that picked up the sag. Hire some drywallers to hang the lid back up and tape--well worth their money if they are available and good. I did my own drywall--vertical isn't so bad, but overhead is a real job.) Budget a week of full-time effort is you have a helper. Hire a dumpster for the debris. Don't forget the visqueen to tape off the rooms--messy work, this.
I have run into this problem frequently. My solution is to remove finish floor and subfloor if their is one. Most old homes I worked on did not have a subfloor.I use engineered joists to replace undersized joists. I remove three joists at a time and replace three.This method will keep the walls from spreading.
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