Reinforce floor joist (from basement) of main floor

Visiting daughter and family in Ks. She has small project for me...Their House (10 yr old) main floor has structural weakness. Floor moves. Only one sheeting 3/4 plywood. Joists (8 or 10's?) 16" on center.
Looking for help. Any ideas?
They had someone look at it and they said they needed shoring?
I think this means bracing between joists...?
I will arrive in two weeks so will have better picture then.

Also plan to finnish basement (1200SQ ') Exposed Cement walls need to be covered. I am planning drywall over 2x2 frame work.
I peeked at DYI who suggested painting and or vissqueen under framing. Looking for ideas...?>

This forum is great idea.
Curtis

 

One question before I answer. When your daughter says her floor moves does she mean up and down or laterally. The reason I am asking is because of the word shoring. Let us know and we will help.

 

Thanks Jack, for your reply. I will check on the floor movement.

After reviewing some posts on the board, (I'm just getting to this) I am moving toward the idea of 2x4 frame with possible R-19 Kraft with moisture barrier between frame and drywall. This will accomodate the electric and some of the inside frame as well.
A full bath is part of the plan. And there is some problem with drains and plumbing exposed in the basement area.
A question; re ceiling drywall, furring was suggested over existing floor joists, maybe I misunderstood??? Do I need to do this?

Sure do appreciate this site.
CFH

 

There is a metal snap in that you can use up in the joist. this will give you the cross brace You should need to stop the floor from going up and down. You didnt say what the span was here? ED

 

I do appreciate your help!!!

Jack; The floor moves up and down! It sounds like this has been quite a problem in the kitchen & dining area as everything in there moves. They had some problem with water (moisture?) around the outside of this part of the house, and it has been some time before they solved this. Upon inspection, during solving the outside problem, it was suggested to do this shoring in the basement area.

Ed; I'm not familiar with metal "snap-in" ? Do I have this right?
Is this something for supporting the joists (16" on C )

Thanks again,
CFH

 

Well....best laid plans etc....

I got running off at the mouth here, trying to get a head start on this project....and I got it wrong. Sorry!

This is the real story. (Where was Paul Harvey when I needed him) The floor joist are something in the nature of TGI's only where the plywood beam is....there is the intermittent 2x4. Does this sound right?? These joists are 24" on C and span 15'. I think that now the problem is beginning to make sense. No wonder they have floor problems....Just one sheet of plywood floor + a type of floor joist I have never heard of + 24" apart and spanning 15'
On top of all that, the inside support of this 15' span is a beam that is delicatly supported on one end by an unfinnished 2x6 wall.
This is beginning to sound like something out of sci-fi.
All this info comes from a phone call from my son-in-law. He is an engineer with a major aircraft Co. After our discussion a few moments ago he's looking for some proffessional help from his end. Some of you may be familiar with this type of joist.
Again, any advice will certainly be helpful.
I'm not sure I have a clear picture of this structure. So any advice and/or clear discription will be helpful.
CFH

 

I'm not sure you're going to be able to fix this. Most builders design their floors to feel solid, not because they are required to by code but because they know that most buyers don't want a floor that bounces. But building codes don't specify solid feeling floors; they only specify structurally sound ones. The minimum structurally sound floor bounces. If a builder is trying to build an economical house, he goes with the minimum.

 

Curtis : That snap in I said about can be called bridge bracing or somethimes its called cross bracing. Like you said 15 ft span you could like put 2 rows of then in all the joist 5' from each other. Another thing we use 3/4 T&G all the time you could put this down on what you have.I dont have the books here now on the TGI's span and load. See if you can find out what the load and span should be for them from home depot or lowes ED

 

The cross bracing would help, but sounds like the moisture problem outside should be dealt with, and approriate drainage installed. Local pro help is maybe the best way to go there. Waterproof the outside of that wall while it's exposed.

If there's that much deflection in the floor, I'd be thinking about adding some support columns in the basement. They can easily be boxed in & finished if the basement is habitable space.

Keep us in the loop. Good Luck.

 

Well, it's unanimous, a tough one to solve for sure.
A thought I have is furring the joists with 1X4 or 2X4 crossways. This would in affect tie-in the bottom of the joists. Drywall on the basement ceiling would reinforce the joists as well.
The other problem with the beam support can be satisfied by reinforcing that wall with plywood sheeting on both sides or scab more studs in the wall or both.
Thanks again, this is plenty of food for thought.
It will be interesting to see how it works out.
CFH

 

Just returned home from this visit. Quite an experience, this basement problem. I will try to explain, briefly, the situation.
(Prior to leaving, the basement was in the finishing stages and ready to paint.)
Some problems found; loose joists. these are 2x4 trusses with spans of up to 16' and held together by the ususal metal plates. Problem in the above floor was the TV set would bounce while walking across living room floor. Upon contacting a local truss Co. it was suggested to place 2x6's across these joists on the verticle 2x4 bridging, right below the top 2x4 runner. This should have been part of original construction. This tied-in all the truss-joists and gave very positive results. Upon further observation I noticed that most of the problem was a result of placing the 4x8 sheething joints in the same place as the ends of the running 2x4's in the truss constrction. These 2x4 ends should be at bearing supports only (in my opinion).
It would be interesting to know if anyone else has had similar problems with this type of truss-joist construction in residence or elsewhere. It appears, in this case, that these metal plates with their teeth-like grip lose their integrity during time and stress of use.
As a retired fireman (LA area) my experience during the 80's when this type of construction was introduced, was that during tests the metal plates lost their hold much sooner, under fire conditions, than regular 2x stick construction.

 

Curtis Hull,

I agree with the fact that the metal cleats do loose their ability to hold after being engulfed in fire but they are quite strong in "normal" use and have been a major factor in creating some beautiful homes. The can span large distances with minimal if no bounce at all. This is all dependant on the proper construction methods used. Having 4x8 sheets that all meet on one truss and are not offset to allow for lateral support to spread over an area effects the performance of a truss. Applying the loadbearing stringback will increase its performance as the truss company said. Alot of builders don't do this thinking that the truss is made and it will do just fine as is - they never read instructions! I rarely do! In some cases, plywood gussets from top chord to bottom will enhance the performace as long as room is available to install minimum 2 - 4 ft pcs. This is one nice feature about Bar floor trusses, you can hide everything up there and finish off a ceiling the way you want without taking away any headroom.

Thanks for the feedback on what you found!

 

Doug;
Just clarifying my discription of 4x8 sheething over the joists. The sheething was laid to accomadate the lateral support, however, the truss runner (top beam of the truss const) had more than one 2x4 runner with resulting end joints (2x4's end to end) tied with a single metal grip. These "joints" were the spots where the problems to the upstair floors were significant. This happened to be where the sheething ( in every case that I noted) joined. This combination notably weakened this support system.
I agree with the contention of benefit of the struss systems. They do allow more latitude in offering open areas that are without all the pillars and posts. I offer this experience as a reminder that may show some of the problems that result from not being aware.

Curtis

 

Thats why we use the Boise cascade BCI joist 24" on center and a 3/4 TG for floor no bend. They have them for just about any span you want ED