I need some advice on a structural problem I have run across in my 100 year old balloon framed house.
There is a 12 foot long wall on the first floor that is suspended between 2-2X8 floor joists with a 12 foot span, the floor joists are 16 inches on center. The wall is supported only by 2X6 blocking nailed between the joists, with the blocking oriented flat ( meaning the depth of the supporting material is only 2 inches). The wall is a structural wall, holding up the floor joists for the second floor as well as the ceiling joists and some of the weight of the rafters. How this has failed to come crashing down is beyond me. Over the years the nails holding the 2X6 blocking have started to pull out, allowing a little sagging of the wall with some resulting plaster cracks.
I was wondering about using an LVL beam directly beneath the wall with support at both ends. I would like to keep it within the depth of the 2X8 floor joists. Is it possible for a 4X8 LVL to carry this load, or do I need to look for alternatives? Assuming this would work, how would I go about supporting this wall while I remove the 2X6 blocking and install the beam?
I plan on getting a structural engineer to look at the situation before proceeding, but am just asking for ideas to discuss with him when the time comes.
Edited 6/4/2005 11:57 pm ET by kid.doc
Replies
Are you certain that this is a structural wall?
Does the framing above actually end atop this wall, or carry over to another?
You stated that it also supports the second floor ceiling and rafters to a degree. How so? Is there another wall supporting these sitting directly above?
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Definitely structural. The second floor joists end at this wall and rest on it. The second floor ceiling joists also rest on it. The wall is at the entry which is open to the roof, so there is no continuation of either the floor joists or the ceiling joists. The rafters continue to the outside wall, which is why I said that the wall supports some of the rafter load.
"how would I go about supporting this wall while I remove the 2X6 blocking and install the beam? "
I take it you mean ceiling?
Build a temporary "shoreing wall" to support ceiling. depending on weight above, here are a couple ways you can go. plate on floor, plate on ceiling. stud under each joist. make studs tight fit. u can simply pressure fit but I like to put one toe nail at top and bottom of each stud. if there's not a whole lot of weight I sometimes go 2 top plates and stud every other joist.
No, I actually meant wall. The wall, with the load it carries from the second floor floor and ceiling are resting on the 2X6 blocking. I would need to support this wall and its load while removing that blocking in order to place a beam beneath it.
ok... I misread.....bleh...that is an ugly detail!
Edited 6/5/2005 1:41 am ET by nails2
ok..now that I've thought about your scenario in the proper sense, I think that I would still go about it the way I described in my 1st post. adding that you would also have to set up shoring on the 2nd floor as well. to support the ceiling joists and rafters.You should make sure that the shoring walls are lined up directly one above the other. That way the most of the load will be taken off of the wall. you may even want additional shoring in the basement/crawl space.
I'm not sure if you will be able to jack up anything that has sagged but if you can, certainly try. Sometimes in old houses things are beyond jacking up, other times you can make quite a difference. with your wall one other thing I might do would be to screw a 2x on flat to the studs having the 2x resting on the joists to help keep the stud wall from settling once all the blocks are removed. your wall will be attached to the the floor system above and the top floor ceiling so between the shoring system and the temporary ledger that is attached to the wall you should be ok.
You might get some other worthwhile ideas, but this is one way I think you could approach the situation.
good luck, nails2
Thanks for the reply, it makes sense.
I would not worry about supporting it and taking out the existing blocks. After having the beam sized correctly, I would simply raise it into place below the blocks ( shim to load evenly if necessary) and use hydralic jacks to force it into place, lifting the blocks, wall, and all above as I go. This would cal for a little bit of cribbing below perhaps.
I presume this is going from under first floor so is a crawl space or unfinihsed cellar? this Q leads to what willl suppor the beam once it is up....
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I picture that his joists are sitting on a foundation wall, with the blocks nailed flush. I'm thinking that the joists will need to get cut back a bit, enough to let in a beam. So he will need to support that wall.
But he will have to tell us exactly how it is. If he can get the beam in using your method that would be great, it would certainly be the faster way to go.
It is an unfinished cellar/basement with a 6 foot ceiling height and a "rat slab", about 1 inch thick on the floor. Future project will be to dig out the floor to increase head room and poring a proper floor (but that is for another decade).
Your way would certainly be easier, but I was trying to avoid having the beam project below the floor joists, and if the blocking is left in place that would only allow a 6 inch deep beam to be used, certainly not adequate for the load I would think.
Edited 6/5/2005 11:18 am ET by kid.doc
Having less depth for the beam simply means shortening the spans it covers by putting in more posts. That inch of rat slab will not support a post, so you will need to dig to pour a footing for each post anyway.Now, about the future project - digging down three feet or so - I will recommend against it unless the foundation wallls you have at the perimeter now are at least that deep. Digging lower to the inside can likely undermine them and cause some other major failures. If you elect to give up that idea, then several interim posts under the beam at about six feet OC should be pretty handy. If the scenario is as nails describes, where this is going to bear on the foundation at each end, you would have a devil of a time inserting it as all one and it would be taller than 8" for sure, but by breaking it into two segments and using a post in the center, you make it easier to insert and you change the design parameters to make it have less height. So to keep all the options open, it looks like maybe you will be digging for a footing for at least one post in the center and it will be a deep hole if you still plan to keep that dig down option openm for the future. Maybe start that hole before the engineer comes. That will let him see the soil and maybe offer an opinion on the later digdown, but structural and soils guys are wearing two different hets usually. One oft he engineering firms here can deal with both
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Thanks for the input. If I can keep the beam within the 8 inch depth, I would be able to get it in with no problem since one end of the floor joists are bearing on top of a center beam and I would be able to slide it in across that beam from the other side. I guess I will plan on at least one post in the center like you suggested, subject to the engineer's approval.
By the way, the future project of lowering the floor will only go down 18 inches, not 3 feet. I will also have to use a small retaining wall (I think they are called Wisconsin walls) along the inside to prevent undermining of the footing. But that is way in the future, I just want to have things done in a way that will not hinder me if and when the time comes.
Here is how I figured three feet. Yopu have six now. To get a finished eight feet, you would need to gdig down to nine feet, to do drainage and gravel base. But if you could settle for a finished cileing of only say 7'2" and you have native gravel already, you are still digging nearly to eight feet which is another two beyond what you have now.
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