I have 3×12 floor joists 16-o/c (50’s ranch) which span 22 feet. The center is about 1-1/2″ low. I have no way of puting a support beam in the basement. Is it possible to jack up the floor from the basement and once level bolt steel plates or steel angle to the sides of the joists. I have the floor exposed so getting to the joists is not a problem. I plan on calling an engineer but I’m looking for someone that has actually done this before. Thanks for any help.
Ed
Replies
It's hard to imagine the situation where it absolutely has to be done with NO beam or posts below. It's only a basement, right?
If the problem is just one of headroom under the beam, you can do a flush inset beam instead of hanging it under the joists. Truly solving the problem for that kind of span will probably mean a deeper joist solution. Flitch plates added to the joists would be very labor and materials expensive. So the best solution is to look for a way of dividing the span to make it shorter. If these joists were installed green, then re-educating them will take time so start jacking right away. Do a little at a time.
I am also imagining that there is some load from above. Your engineer will have to pay attention to things all the way to the top to solve the problem in the basement.
We took carte of one like this with a 28' span in a great room by inserting a flush beam and supporting it with 7/8" steel rods gointg to the attic with a beam placed there under the ridge beam. If I remember, it was five LVLs 18" H wioth those steel rods hidden in walls on the second and third floors.
Excellence is its own reward!
Man, that desciption of the installation technique for the 28' flush beam sent me reelin'!
Then I got to wondering how far apart the steel rods were placed? And what kind of beam was placed under the ridge beam? Let the thunder crack and the waves roar.
We're going on.
Rez, there were locations in the attic where we could load to posts running all the way to the basement at the ends of the inserted beam. There were two steel rods spaced approximately at ten, eighteen feet.
To get that beam material in, we cut a gable end vent in the end and had a boom truck do the delivery. Slick as snot on a glass doorknob!
It was all the drilling to bolt and assenble that killed us..
Excellence is its own reward!
"The first rule is to keep an untroubled spirit. The second is to look things in the face and know them for what they are." --Marcus Aurelius
Piffin, unfortunately the basement is our family room with a finished plaster ceiling. plus there is no where to set one end of the beam since there is a 7 foot fireplace where the it would have to go. Looks like the cause of the problem was a 36' Sub-Zero and a double wall oven which was probably added during a 70's kitchen remodel. In any case I was hoping I could take some of the bow out with material sistered to the sides of the joists.
EDJW,
We actually did it both ways. One with the basement ceiling exposed and the other way with a finisned basement with sheetrock ceilings.
Basement ceiling exposed was about 21' span with 3x10's. We assistered 1-3/4" x 9-1/2" microlams. Befor we nailed them we jacked up each beam and nailed them flush to the top of the new microlams.
Sheetrock ceiling we couldn't touch so we worked just from the top we put our microlams in and assistered them to the existing beams.
These were both in open rooms I don't know your situation. You also might have some pipes/wires/duct in your way but if you want a straight floor you have to move some of these things and then put them back in later. It's like doing some Add-A-Levels.
Hope this helps.
Joe Carola
Joe, I did one like that where the original was rough 2x10 @ 20"oc spanning 18' or thereabouts. We jacked each joist straight and sistered LVLs to them. Expensive but it works. You could park an elephant up there now..
Excellence is its own reward!
"The first rule is to keep an untroubled spirit. The second is to look things in the face and know them for what they are." --Marcus Aurelius
Framer,
Did you run the microlams the entire length of the old joists? This seems like the best way to do it, but one end of my joists sits in the web of a steel I beam and the other end is in a pocket of the exterior concrete block wall. Do you think this method would still work if I just sistered the microlams without going from end to end? I saw something like this done in a This Old House Magazine where they sistered LVL's to the sides of the joists to level the floor and they said it also added quite a bit of stiffness. Thanks very much for your help.
Ed
What is the debth of the I Beam? How much bearing on the I Beam would you have?
Also on the other end too. Same question as above.
Joe Carola
Ed,
I forgot to mention that I did run them all the way through but they were sitting on tthe sills on top of the foundation.
They don't have to be full bearing 5-1/2" if you have a pocket it will be hard for you to slide them in. You can have 2" minimum bearing at least in New Jersey.
So if you have a decent amount of debth in your beam pocket and web you can cut the beams to your minimum bearing and slide them in alot easier.
One side there was 8" block and 5-1/2" sills we had about 2-1/2" of block left over we were having problems getting the beams in so I cut them a little shorter to were they were about 1-1/2" on the sills then we went back and slid 2x4's on top of the foundation underneath the beams the hole lenth of the foundation to give enough bearing and support.
Let me know what you think.
Joe Carola
Ed,
Is this just one spot of the floor?
Maybe like an 8' or 10' section?
So how do you plan to get to the joists with a finished plaster ceiling????????.
Excellence is its own reward!
"The first rule is to keep an untroubled spirit. The second is to look things in the face and know them for what they are." --Marcus Aurelius
Piffin, I have the floor opened up from above. I like the idea of sistering LVL's to the sides, but like I said to Framer, running them the entire length may be a bit of a problem. I'd have no problem getting them into the web if the I beam but getting them in the block wall will be a problem. I'm hoping to at the very least level the floor and add a little support. The fridge and ovens are not going back in the same place. -Ed
Ed, Those 36 foot SubZeros do get to be pretty heavy, don't they?
It is possible to jack up from below with a finished ceiling. I use a 4x4 and wrap it with old carpet to pad it and keep scuff marks off the SR. Then we set it up with other 4x4s for posts on hydraulic jacks and pump slow, checking for damage.
Cautions,
The pump posts have to be plumb and the base for the hydraulic jack must be level. Otherwise the post can kick out explosively. If you have a good floor, you should protect under it with a scrap of plyu and then a 12"2x12 or 2x10 to spread the force.
The padded lift beam needs to be positioned perpendicular to the joists..
Excellence is its own reward!
"The first rule is to keep an untroubled spirit. The second is to look things in the face and know them for what they are." --Marcus Aurelius
Ed
As you surmise the floor joists have been overlaoded, hence the 1 1/2in sag. Be guided by your engineer in whether you can retain or have to replace the joists.
Once the joists are back to level it is the very bottom fibres of the joist that have to be reinforced for the span / load. This can be done with a thin steel strap, possibly thinner than 0.05 in - something like a 10ft long nail plate. Cause it is likely that the ceiling in the basement is already damaged, or will become so as the repair procedes I would be prepared to remove enough to get to the underside of the joists. Then again I'm an engineer (earthworks and roads, not structural) and like a lot of engineers believes in belts and braces.
Your engineer may like to know that the organisation I work for is looking to strengthen some concrete bridges so they can carry heavier trucks. One technique to be used involves glueing a carbon fibre mat to the underside of each girder.
Let us know how it turns out
Ian
0.05 is awful thin, not necessarily for tension but the bearing/deformation on the end shear bolts .
Done the steel strap built up beam on everything from 2X10s to 6X14s.
5" wide 1/8 steel strap on 6X12 doubles the strength and nearly triples the stiffenss. Same true of r2-1/2 inch strap on 3X12.
Caveat is it takes a lot of bolts.
For 22 ft 3X12, 2-1/2 wide 1/8 or 3/16 thick steel strap will fix you up, light and manuverable to get in place.
Now the bad part. You need to install about 50, yes fifty, 3/8 lags for it to work well. Space about 3" oc near the ends and as far apart as 1 foot near the center (the shear is greatest at the ends). Drill the strap, position under 3X12s, jack to 1/8 to 1/4" above level, install bolts, remove jack = flat floor.
If you don't have a drill press and an air impact or big 1/2 drive to run the bolts, this is too labor intensive for normal DIY, with drill press and driver, only takes 1/2 hour.
Trying to learn here...
How long would the 3/8" lags be and would pilot holes for the lags be necessary and if so at what diameter? Let the thunder crack and the waves roar.
We're going on.
Junkhound,
This sounds very doable. I have a drill press and an air impact. Just a couple of questions: How long should the straps be? Would using steel angle be overkill? You said to "position under 3x12s", I'm assuming you mean at the bottom of the joist bolted to the side. What would you recommend for the bolt pattern? from what Ian was saying about the .05 thick steel, I do recall the engineer saying something about using steel studs to do this, but I kind of like your approach better. Thanks very much for you reply and to everyone for their input. -Ed
If you can't put a new beam at mid-span because of the fireplace, what about putting it off-center, maybe at the 1/3 point? The loads would be unequal, but I would think that reducibng the span by 1/3 would make a big difference in the deflectio of the joists. And of course the part that was reduced by 2/3 should be enough to support a truck. If possible, offset the beam to the kitchen side to pick up the weight of the 36 ft fridge. Bet you can pack a lot of ice crream in that baby!
ELCID72,
I was really trying to stay away from the beam due to head room and keeping the look of the existing family room. I really like the idea of the steel straps that Junkhound was talking about. I guess I did say 36 ft fridge but it was only 36 inches. I hate when I forget to use the shift key. -Ed
I should let the junkhound answer, but in his absence I believe that he suggest's that the strap is on the bottom edge of the joist, so you are going to damage that ceiling again. Hope I am wrong, but he mentioned flat, and I pictured it on the bottom. Good luck!
Dan
Handydan, now I get the picture. I was really trying to avoid tearing up the ceiling as much as possible. I may look into to LVL solution that Framer was talking about. I'm going to get in touch with an engineer and I'll let you know what he says.
I talked to the engineer today and he suggested either jacking up the joist from 3 points below and through bolting a 6x3x1/4" angle approx 12 to 15 feet long to the side of the joist at the bottom edge, or going with the LVL method that Framer had posted. If I go with the LVL's I wouldn't have to jack up the joists just sister to the sides provided I can support them on both sides. I'll have to take up some more of the subfloor to see if I can do that. The only other obstacle that I'll have to overcome is that the LVL's will have to go under 2 partition walls, so I'll have to figure out how to get those up to get the LVL's under them since they have taken the same path as the floor. In any case since I'm in the process of doing a complete kitchen remodel and want to put hardwood on the entire 1st floor I'm determined to get this done. I want to thank everyone very much for taking their time to respond to me with their opinions and suggestions. I'll let you all know how it turns out. -Ed
Ed,
I don't know the layout of your room but you can cut the shoe (Bottom Plate) of the two perpendicular walls out of the way and drop the LVL'S in flat do what you have to do and put the shoe back.
On the top of each end of the LVL'S you can cut them on an angle so that it makes it easier when you tilt them up into place.
A little banging on each end with a sledgehammer should help.
Hope this helps.
Joe Carola
Framer, thanks for the tip. that will definitely come in handy for getting it in the web of the beam. It also appears that I got lucky, the other end of the LVL will sit on top of the block wall which will make it much easier to put in place at the other end. The engineer that I spoke with seemed to like using the LVL's. Thanks for all your help, I really appreciate it. I'll let you know how it turns out. -Ed
Any chance you can poke a hole in the block wall and slide the lvl in from the outside?
Well, I was thinking that you wouldn't mind making a mess to solve the problem. I had envisioned cutting the floor joists and installing the new beam up tight under the subfloor, then hanging the old joists off the new beam with jooist hangers.
Junkhound
Was guessing at the required thickness as it's years since I've used the my stress tables. The thickness issue is two fold, thick enough so that there is enough steel to carry the load, not so thin that the strap tears around the bolt holes. I'll be guided by others as to how thick the strap needs to be. However, the strap doesn't need to go the full 22ft span, just most of it, so the joist doesn't need to be reseated. The strap reinforces the beam in mid-span so that it doesn't deflect too much under the applied load, at the ends the joist is in shear and the existing timber should be plenty strong enough.
For Ed, the strap technique requires access to the underside of the joist. Attaching a steel angle to the side of the joist is possible. You will need to get the angle as low as possible on the joist and bolt through. I'm real unsure of things like bolt spacing and the risk of the bolt holes elongating under load, potentially splitting chunks out of the timber.
Ian
Hope I cover all the queries.
1. I use 3-1/2 lags (primarily 'cause I get that size free off pallets and have buckets full of 'em). Strap bolted to bottom edge of the beam into the edge.
2. On D-Fir or pine, I don't use any pilot hole for the 3/8 lags for a 3by or larger, have used a 3/16 pilot for 2 by.
3. Channel is fine, although you do NOT want to bolt thru the side, you want to bolt into the edge. The reason is the bolts are there for shear, and the farther from the stuctural center (like center of gravity) the better - bolting thru the side is like shaving that much height off the beam.
4. I'd use a 20 ft length as that is a standard size and you would not have to weld on pieces.
5. Best text I've seen on basics of built up beams (either with the strap bolt on steel or built up boxes made from plywood and 2by stock) is Timeshenko & Young's "Strength of Materials"
6. If you have the headroom another option is a steel cable and big turnbuckle. Tie cable near top of beam ends (separate problem in itself), but a 4X4 block under the center fo the beam with stel bearing surface, tighten t;urnbuckle to make an inverted truss - Boss Hog likely could tell you all the details on this option, it's a standard (or used to be in the 60's) insurance company "we'll pay for this fix but nuthin' else" for sagging barn beams in the midwest.
PS: Learned the strap technique when I was a kid way before I ever saw the formula in engineering classes. A CE my dad worked with on the railroad showed him how to triple the strength of a oak 6X10 (true size in old house) by bolting on a length of 6" angle salvaged from a water tower (when steam engines went out in the 50's) - he used 4" long 1/2 lags with 3/8 pilot in the oak. Pop had to plane away the edges of the 6X10 to fit inside the channel - inverted would have been even stronger, but would have required digging another 3" out of the crawl space to get desired basement headroom. Was on a tour of an old 1870s building ready for demolition once, the guide said (tounge in cheek) the reason there were more rivets on a built up beam (angles and sheet) at the ends rather than the center was "they ran out of rivets"
So you've saved the plaster ceiling........will it still be worth saving after it is raised an inch and a half during the jacking process ? They usually aren't.............carpenter in transition
Timeshenko & Young ...
now there's a name I haven't seen since I did Structures 25 years ago. have since mainly worked with long flat structures like roads
From the other posts it looks like Ed is trying real hard to avoid jacking the joist level 'cause he doesn't want to damage the ceiling in the basement. This also precludes reinforcing the bottom face of the joist.
Ian
Actually, I mispelled the name.
Timoshenko, Stephen, 1878-1972.
IMHO one of the best structures researchers ever. His basic texts even let us calculus challenged people get a good insight into how stuff bends and breaks.
Had to look up when he died as could not remember that date, thought it was in the 60's as the copy I have is a '59 edition, lots of texts by him in 20's/30's.
Ceilings and plaster - gotta crack eggs to make omlets, or - gotta crack plaster to get stuff straight. When my brother took the sag out of first floor of his 1910s house with the strap technique, he cracked the ceiling plaster on the SECOND floor!
know what you mean.