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  1. #31
    Join Date
    Aug 2009
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    St. Paul, MN & Northern WI
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    267

    Default Re: Crushed central bearing beam

    Kevin:
    It’s hard to imagine that they would not have headered the jsts. off around the chimney opening, but certainly not impossible. And, as you suggest, that would make those jsts. act like long cantilevers, and bring much more load/reaction back to the center beam, from both of the spans. The thing I meant by the 2x pl. (like a sill pl.) at the crushed beam bearing area, is that it bridges that crushed area, since you have no way of cutting and fitting a new stud there for good end bearing, both length and exact shape. But, you might still need more studs to make up the needed end bearing area. Otherwise, it will act o.k. as a shear wall with the 3/4" plywd., but the plywd. would not be expected to carry that concentrated vert. loading too. When you do this extensive new shear wall retrofitting in the found., don’t you also try to do some re-leveling in process? I do understand that’s extra work and time, but it would lead to an improved finished job, wouldn’t it? And, I also understand that you can’t always get rid of all of that old settlement, you just have to live with it, short of completely gutting the house. Then tie-downs into a weak framing system, not intended for them, is another real difficulty.

    DickS:
    While the self weight of that battered found. wall will be slightly to the interior, the wall loads from above are probably slightly offset to the exterior, so you might not really have much eccentric loading to cause that wall to roll. You’d have to see it in the flesh (I mean in the soil) to determine otherwise. Also, if you think of it, a slight out of plumb or rotation will not change the elev. of the top of the wall by much. You might see some of this rotation by looking at the sill pl. If it had gap at/along one corner/edge and crushing or was tight at the other edge, that might indicate some rotation of the wall. i.e. with the rotation of the top of the wall taking place btwn. 11:00 and 1:00 o’clock the elevation of the top of the wall doesn’t change much. I think the bigger issue with those old found. walls, was that they were built in a pretty rough fashion, probably not reinforced or well interconnected. Then they were built to different soil bearing levels (and probably diff. soil cap’ys. at diff. levels too), over a number of years (or additions), and without much regard for consistent soil bearing cap’y., or the potential for settlement. They moved around quite a bit, and the construction was loose enough to tolerate most of this movement, and the people tolerated it too. They certainly should do something with the exterior grading and drainage to prevent water from running under the founds. and ponding in the crawl space. Those old bldgs. are interesting to work on (damn tough to put a fixed price or time on), when every time you turn around, there’s another nasty condition which requires a new fix detail. You need a really knowledgeable builder who has a good working relationship with an on call engineer, who’s done this kind of work and is willing to jump each time a new issue comes up.

    I rail a lot about all the new technology, but the fact that a contractor can e-mail me a few photos of the condition, so we have something in common to point at as we talk, certainly saves trips to the site. Once I’ve worked with a builder for a while, so I know how he explains things, we have a fairly common terminology, so I know what he knows and the quality of his work, and so I know how he interprets what I tell him to do, we can respond pretty quickly to keep the work moving. But, I still like to get out there and see and touch it so we know there was no misunderstanding about what was to be done.
    Dick Hackbarth, PE
    RWH&AI, Consulting Engineers

  2. #32
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    Apr 2008
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    Default Re: Crushed central bearing beam

    Quote Originally Posted by Dick Hackbarth View Post
    Kevin:
    It’s hard to imagine that they would not have headered the jsts. off around the chimney opening, but certainly not impossible.
    There was an effort at tying things together, but they didn't have a double member header tying into doubled joists. It was enough to prevent real failure, but not enough to properly carry loads around the opening to ground. You'll see a lot of that type of work on these older houses.


    Quote Originally Posted by Dick Hackbarth View Post
    The thing I meant by the 2x pl. (like a sill pl.) at the crushed beam bearing area, is that it bridges that crushed area, since you have no way of cutting and fitting a new stud there for good end bearing, both length and exact shape. But, you might still need more studs to make up the needed end bearing area. Otherwise, it will act o.k. as a shear wall with the 3/4" plywd., but the plywd. would not be expected to carry that concentrated vert. loading too.
    Yes, I understood what you were saying- it's not a bad idea. I was able to get a 4x6 "post" in the place of the 2x4 "cripple stud" I took out in the tight zone, so it is already better in terms of bearing area. When the 3/4 ply goes on (1 1/2" o.c. edge nailing) that whole wall will definitely get stiffer carrying loads in all directions, if one is thinking of it as a "beam". In terms of the direct path of load from joist->4x6->stud the 4x6 is not a "beam" generally speaking, of course.

    I will definitely report on whatever the engineer says.


    Quote Originally Posted by Dick Hackbarth View Post
    When you do this extensive new shear wall retrofitting in the found., don’t you also try to do some re-leveling in process? I do understand that’s extra work and time, but it would lead to an improved finished job, wouldn’t it?
    Well, that's an interesting question. In this case, you could make an argument that the improper redirection of the load path may make the shear wall system perform *better*.

    That's a weird statement- let me explain.

    In this crawl space, there is a sort of "hall" that runs next to the center bearing wall. When the "hall" was excavated, a new retaining wall/foundation was poured under the center wall. That newer concrete work is better quality top-to-bottom than the perimeter footing, which is a newer cap over original battered footings.

    Our marching orders call for a 20' shear wall along that center section. 3/4" ply, 1 1/2" edge nailing, nailed into the 4x6 at the top and into new 4x4 blocking at the bottom, with 4x4's at panel edges/splices. 5/8" anchor bolts at 16" o.c. through the 4x4 blocks into the better concrete.

    So I could make the argument that having (improperly) shifted the floor load to that center bearing wall will actually make our lateral-load work perform better- the larger inertial load is going to happen at this nice long shear wall in decent concrete.

    There are other issues, of course, but it's not always clear if the oddities we find are making our new systems work better or worse.

    Quote Originally Posted by Dick Hackbarth View Post
    And, I also understand that you can’t always get rid of all of that old settlement, you just have to live with it, short of completely gutting the house. Then tie-downs into a weak framing system, not intended for them, is another real difficulty.
    Yeah, it's pretty rare to attempt to take more than a 32nd back here or there. The settling has usually occurred over decades, and has often been compensated for with new plaster, doors shaved into parallelograms, etc. Trying to correct it can lead to loads of problems, unless it is a total gut, as you said.

  3. #33
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    Apr 2008
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    Default Re: Crushed central bearing beam

    [QUOTE=m beezo;696390]
    Quote Originally Posted by kfc510 View Post

    Heh. Level sill plates and joists.
    An interesting concept, but not really germane to the work I do.

    /QUOTE]

    so true of a lot of houses. Not sure why I even carry a level somedays except to see just how bad it is. That and to decide if we can get it close or if everything we build is going to be 1/2 a bubble off so it looks like it belongs in the house.
    I knew you'd get it, Beezo. Yeah, it's a real art to know when to build level and when not to, or how much to try to win back. Square, too.

  4. #34
    Join Date
    Jun 2004
    Location
    St Louis, Mo for the past 25 years
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    7,336

    Default Re: Crushed central bearing beam

    Level. plumb and square can look so out of place when you are working on something along the carnival fun house. However a compromise between the two can look and work just fine.

  5. #35
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    Default Re: Crushed central bearing beam

    Quote Originally Posted by Dick Seibert View Post
    Dick:

    I see from Kevin's sketch above that the perimeter foundation is an unbalanced battered foundation,
    Good eyes, btw, Dick. (Also an indication of the red flags an experienced builder around here will look for- original battered foundations are often seriously deficient here.)
    Last edited by kfc510; 11-24-2013 at 07:02 PM.

  6. #36
    Join Date
    Sep 2005
    Location
    California Gold Country
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    22

    Default Re: Crushed central bearing beam

    Hey Kevin,

    Thanks for making the introduction--perhaps I'll run into you under a house sometime.

    It looks & sounds like you're on the way to pinpointing the mystery. Rotating footings, gophers, posts sinking into termite colonies, and all the rest can cause some seriously sagging framing. That puts a lot of load on the undamaged structure that remains.

    I used to work in an old Victorian that was converted to commercial use. The floor in my boss's office sloped 7 inches across the room. Finally he got tired of the wind blowing in under the wall and spent 50 grand to re-level the building, at least most of the way (as you know, you can't take out 50 or 80 or 100 years of sagging in a week or two).

    Cheers! Enjoy the holiday--

    Thor

  7. #37
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    Apr 2008
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    Default Re: Crushed central bearing beam

    Quote Originally Posted by Thor M, Structural Engr. View Post
    Hey Kevin,

    Thanks for making the introduction--perhaps I'll run into you under a house sometime.
    Cheers! Enjoy the holiday--

    Thor
    Good to e-meet you. I'd like to buy you a beer or tea or aloo tiki cholle at Vik sometime. I'll p.m. you my contact info.

    I'll update this thread when Ralph comes out and has a look. The job's in the Elmwood, if you're curious.

    If you get a moment (and have interest) maybe you can weigh in on the "structural plywood" thread. Ashby Lumber says 3/4 CDX is the same stuff as 3/4 struc 1; Truitt and White specifically disagrees.
    http://forums.jlconline.com/forums/s...471#post696471

    Happy Thanksgiving!
    kevin

  8. #38
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    Apr 2008
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    Default Re: Crushed central bearing beam

    Ok, time for an update. Nervous Nellies be warned, this one is fun too.

    We pulled down more of the soffiting/ceiling boards that were up, and exposed the undersides of the joists at that center bearing wall. Check it out:
    Attached Images Attached Images
    “It is difficult to get a man to understand something, when his salary depends on his not understanding it.” - Upton Sinclair

  9. #39
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    Apr 2008
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    Default Re: Crushed central bearing beam

    So we had our final inspection this week. Engineer has been out 3 times since we first encountered the crushed beam, and once since we uncovered the crushed joists.

    Only fix he recommended was a slightly more secure vertical load path through the blocks that go on top of the 4x6 up to the subfloor in the 3 joist bays at the affected joists.

    AFAIK that's all that will ever be done in that area.
    kevin
    “It is difficult to get a man to understand something, when his salary depends on his not understanding it.” - Upton Sinclair

  10. #40
    Join Date
    Apr 2008
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    SF Bay Area (East Bay)
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    Default Re: Crushed central bearing beam

    So we had our final inspection this week. Engineer has been out 3 times since we first encountered the crushed beam, and once since we uncovered the crushed joists.

    Only fix he recommended was a slightly more secure vertical load path through the blocks that go on top of the 4x6 up to the subfloor in the 3 joist bays at the affected joists.

    AFAIK that's all that will ever be done in that area.
    kevin
    “It is difficult to get a man to understand something, when his salary depends on his not understanding it.” - Upton Sinclair

  11. #41
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    Apr 2008
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    Default Re: Crushed central bearing beam

    Here's the last couple of shots I have of the situation, just to complete the thought.

    Pic 1 is a re-post of the joists and bay over the area with the intense load.

    Pic 2 is a shot of the final detail in the bays- we installed new 4x8 blocks in each bay, glued to the subfloor. The engineer lets us cut the blocks a little short in height to allow us to slip them in without losing too much glue, and then shim them up tight to the subfloor.

    In the three bays at the affected area we were told to well fill the resulting gap between the bottom of the block and the top of the 4x6 beam/girder/top plate with epoxy where the shims are.

    And the blocks get lapped by the 3/4" struc 1 shear ply from the shear wall.

    Pic 3 is looking back at the affected area. The crush zone is directly across from the chimney. The HO repaired the tile work in front of the hearth a while back; you can see his newer framing projecting below the existing joist plane. Note the bent gas line in that area.

    Maybe there'll be more done on it later, but for now that is all she wrote.

    kevin
    Attached Images Attached Images
    “It is difficult to get a man to understand something, when his salary depends on his not understanding it.” - Upton Sinclair

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