Hey All,
I took a look at a potential project this week and I need some advice regarding the specs of a support beam I want to install. The homeowner would like to get rid of two exposed beams and a small wall downstairs in order to create an open floor plan. In order to maintain ceiling height, I’m planning on setting up temporary supports and cutting a channel in the existing floor joists. I’ll install some LVL’s and reattach the floor joists with hangers. My question is: how many LVL’s and what size should they be?
Some more specs: 2×8 full dimension floor joists that are approx. 26″ o.c.. (I work on old VT houses!) The span of the beam will be approx. 24′ long. If anyone is willing to share some advice and thoughts, I’d greatly appreciate it.
Keep up the good work, Rob
Replies
six.
and make them big.
and probably longer than 24ft.
might need 8 ...
so get a coupla extra's ...
just in case.
Jeff
Buck Construction
Artistry In Carpentry
Pittsburgh Pa
You should not be giving this errant advice.
I typically use yellow pine 2x6's screwed together with a bunch of liquid nails Heavy Duty. This saves weight so the foundation will not settle. LVL's are expensive and heavy...
Why so big? I think 2x4's are cheaper.
well ...
U got me there.
but framer52 has a point also.
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
What makes your advice any less errant than Jeff's?
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Not enough info.
sq. ft. of floor being supported?,
point loads on existing floor?,
span of joists?, (both current and anticipated)
bearing walls supported on floor?
O.C. and size of joists are useless without all of the above information.
Plus how are you going to support the ends of the new beams?
Eventually someone here will suggest taking all that information to a structural engineer so I might as well be the one to do so.
Talk to a structural engineer after getting all the info together.
On going project I am on is replacing a rotted triple full 2"x12" beam..spanning 26' 7" on block corners..the whole shebang is holding a walkout porch of 2"x12" joists, 2 layers of 1" decking, and had built up roof..big azz load. Plus a stucco cieling.
I was considering LVL, or steel, or a flitch plate and LVL..wasn't too sure what the hell to do. Finally fessed up to the HO's and said we need an eng.
Probably the best words I ever said, they were Ecstatic that I knew when to say when, and they gladly called one of the best around. He promptly came out, surveyed the situ, told me I was dead-on..but the LVL would jhave to be deeper like 14" not 12" that existed..so steel is a better option.
I'll have the drawings tomorrow, and I can then free my mind of how the hell I am going to get the old rotted beam out, and insert the new steel..
Don't know how much the cost was, but it has to worth it, just for peace of mind and absolution of responsibilty on my part.
I also have to sister a few rotted joist resting on this succker, and he is supplying the bolt pattern for the steel splice plates..how cool is that?Spheramid Enterprises Architectural Woodworks
"Welcome to Poo-ville, can I have your socks?Seriously Folks, I need a home for 3 lovers of your life.
That's the way it is supposed to work. Boy doesn't it feal great knowing you were right.
No kiddin. And the Ho's level of trust went up a notch. I ain't to proud to call in an expert..(G)Spheramid Enterprises Architectural Woodworks
"Welcome to Poo-ville, can I have your socks?Seriously Folks, I need a home for 3 lovers of your life.
Thanks for the reply. I sort of knew that I didn't have all the info I needed ( and that I needed an engineer!) but I wanted to throw it in to the forum anyways. I've done projects like this in the past as the lead carpenter but this will be my first as the GC. I'll need to ask around to find a decent engineer to work with and I thought I would get some advice from you all in the meantime. I'll gather more info and make some calls this week.
Rob
I do not know what kind of building inspectors you guys deal with but with out a engineer's stamp on the plans I would not get a permit or approval. So I would not even bother to guess and I have 15 years on my own and 10 years before that working for other builders.One recent example: was a Master bath remodel over a garage I was hired to add a master bath with a custom shower, new walk-in closest, large tub and a new bay window addition to the a master suit. But before I could start that I had to fix the 10 inch sag in the floors over the center beam of the garage.Some one removed the center post of a 2 car garage and replaced the two smaller doors for one large one. The center beam itself was just 3 2x10s with a 2x2 ledger nailed to support the 2 x10 joists notched to rest on it. and a joint in the middle of the beam It was no wonder it sagged a full 10 inches.Now the architect specified 3, 18" 22 ft. LVLs over the door and then two new beams from front to back on each side of the center beam to support the floor joists. Then I had it engineered. Approved plan was 3, 24" LVLs through bolted every 8 inches over the door opening then 6 beams 3 each side of the center beam. made of 2 18" LVLs running front to back to support the floor joists completely removing the load from the center beam.Even with my experience and the architects we still were glad we had it engineered.PS I forgot to mention the home owner did not want to just put the post back which were removed that would have made it easier but they liked the open space. (big SUVs)
Edited 4/6/2008 11:56 pm ET by MFournier
No problem. A good engineer that you can work with, is responsive when needed and is willing to listen is worth their weight in gold. I was lucky to have met one early on who helped me out of many a problem. It is worth learning to do the load calcs for yourself, always worth knowing and really not difficult to do, but that never replaces the engineers stamp when it comes to the BI.
They can't get your Goat if you don't tell them where it is hidden.
It sounds like you are capable of providing the right information. Any yard that sells LVLs is capable of sizing it with the software from the manufacturer.In addition to what you first threw out, you would need all the extra info that Dovetail detailed.I use an engineer when there is unique design requirements.
Those old full 2x8s at 26oc might make this one of those. They are slightly overspanned now if they are loaded above other than just floor space. I'm imagining a possible cape with kneewals transferring roof laod down, but might be a vernacular farmhouse with open clear span.
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If you really want to span 24', a steel I-beam might be a better choice. You can save some height that way. Have your supplier size it for you. Assuming there is quite a load above it, wood is not going to do it for 24' without at least one support, even if you follow the advice to put in eight!
Just glue some 2X lumber onto each side of the beam with construction adhesive. Order the beams with holes predrilled, and then drill through your lumber one side at a time, that is, glue the lumber on one side, drill the holes from the beam side, then glue on the other side and drill the rest of the way from the first side you glued. Then use some half inch bolts, washers, and nuts to secure everything before the glue dries. Now you can attach the hangers.
No matter how tight you jack up and support the I-beam and how tight you nail up the joist hangers, there will be a slight sag in the joists at the hangers when you remove the supports. It won't be much, but if I were doing this job, I would push each individual joist up almost an extra 1/4" with a floor jack before attaching that hanger. This would be a tricky operation, depending on what is above that joist. The direction of load bearing walls above could have a significant effect, as well as how many floors there are above. Also, move any weight on the floor above away from the beam while you are doing this operation.
Don't raise the beam itself a 1/4" to compensate, since the sag will take place at the hangers. You would just end up with a hump in the floor.
Also, since you are working on an old house, you should be aware that the concrete in the basement may not support the point load of a floor jack at some spots. I would recommend getting some steel plates to place under the jacks, I'm guessing at least 2' square. Just go slowly on this, lifting each joist just a little bit.
Having said all that in the last paragraph, I would really recommend a different method. This will eliminate worry about the basement floor being able to hold without cracking. Build a temporary wall on each side of the beam location, maybe two feet away. Use 2X6s for top and bottom plates and studs. Temporarily nail up the plates to the joists, and put the bottom plates in place. Then cut the studs just a little longer than the distance between the plates. You will know how long by how hard it is to knock them into place. You don't have to nail them in. Use a sledge and some scrap 2X6 material to move the studs into position under the joists. Then you can use just a few floor jacks to work your way along the beam to raise the joists just enough. How much and how long depends on what you find as you move along.
This is also a good time to correct any dips in the floor above, if the rest of the structure will allow. The roof could be the biggest player in your decision here since it is an old house.
Three years ago, I bought my current house. The framer had placed the main beam in the basement four feet away from the main supports for the second story. Over twenty years, the floor sagged and the floor joists bent while trying to support two stories above without adequate in-line support from below. I got a good deal on the house, partially for this reason. I knew how to jack the floor up from below to get everything aligned, but I ran into one serious problem.
Two years before I bought the house, the original shake roof had been replaced with standard shingles. This required nailing an OSB deck over the strapping that had supported the shingles. That deck tended to have a monocoque effect, as in when aircraft get a major part of their strength from the skin as applied to the structural members. So the roof basically resisted any further changes to the house geometry.
I used about 18 floor jacks to raise the first floor about 3/16" per month. I had about two inches to raise in some areas. I was never able to get the final part done to my satisfaction because the strength of the new roof decking was incredible. So I stopped short of perfectly level to prevent further problems.
You're probably falling asleep by now from reading such a long post, but maybe it will keep you out of trouble.
Good Luck!
Thanks for the long post Sasquatch. I've had some experience installing retrofit beams before and I really appreciate your advice because it is exactly what I was planning on doing.... build two temp walls and crank each joist up an extra 1/4 inch before putting on the hanger. I didn't always do that in the past but that is the way to go. After the engineer takes a look!
Rob