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Bowed purlins, Sagging house

excaliber32 | Posted in Construction Techniques on October 29, 2009 05:59am

The new roof is on the old addition, most of the plaster is down, and now we move to the basement and secure it.

There are two girders that are 4×8 about five feet apart that span well over thirty feet. The floor joists sit atop them and span about twelve feet to the foundation on either side. The original pier foundations are made of brick and have all but washed away due to water infiltration. We are going to jack up the girders and level them–adding 4×4 posts every six feet to replace the original brick piers and steel lally columns that are either too far apart, or kicking out.

Here is my question. The house has settled quite a bit, and I’m concerned that jacking it up might prove devastating to the purlins. There is quite  a bit of bowing in them, and they have rested in that bowed position for years. I thought about scabbing onto them, and then jacking them up. Any other suggestions?

Reply

Replies

  1. User avater
    Dinosaur | Oct 29, 2009 07:02pm | #1

    I seem to have come into this movie partway through, so please excuse my confusion. But if you've put a new roof on an old addition, why are the purlins sagging?

    Dinosaur

    How now, Mighty Sauron, that thou art not brought
    low by this? For thine evil pales before that which
    foolish men call Justice....

    1. excaliber32 | Oct 29, 2009 07:18pm | #2

      Oops, it should say bowed girders. The original floor joists on the house. Some "renovations" involved cutting half of the floor joists for a stairwell, with no additional structure added. Its a mess.

      1. User avater
        Dinosaur | Oct 29, 2009 08:03pm | #5

        We're gonna hafta agree on terminology before we can get anywhere!

        What are you calling a girder--those 4x8 thingies? I usually call them beams.

        What are you callling floor joists-- 2x thingies sitting on top of the 4 x 8 thingies?

         

        So many thingies, so little time to name them all....

        ;o)

         

        Dinosaur

        How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....

        1. excaliber32 | Oct 29, 2009 09:34pm | #8

          Quit being a dousche-bag, please. A girder is a beam.

          1. Piffin | Oct 29, 2009 09:51pm | #10

            What is it in french? 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          2. jimAKAblue | Oct 29, 2009 10:21pm | #11

            A girder generally implies something other than a beam. With that said, a beam could be a girder and a girder could be a beam.

          3. User avater
            Dinosaur | Oct 29, 2009 11:05pm | #13

            Geezus, pal-- if yer gonna insult me, at least spell it right.

             

            As Jim said, a girder ain't necessarily a beam and vice versa. I teased you a little because you already mixed us up by referring to purlins which weren't. How do I know what you mean when you say joists? The way you've been going so far, you might be talking about fire stops, studs, or lintels for all I know.

            Dinosaur

            How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....

          4. Hudson Valley Carpenter | Oct 30, 2009 12:35am | #15

            Look!  He's talking to frenchy about it now.   We can sneak out the side door and "no one will be the wiser" (literally).

          5. User avater
            Dinosaur | Oct 30, 2009 05:11am | #20

            Look!  He's talking to frenchy about it now.   We can sneak out the side door and "no one will be the wiser" (literally).

             Dammit, man! Now I gotta wipe all that coffee which spewed outta my nose off the screen....

            Dinosaur

            How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....

          6. jimAKAblue | Oct 30, 2009 05:18am | #21

            I didn't finish the entire sentence till you reposted it. It is quite funny. Frenchy, we're not laughing with you....err...something like that.

          7. User avater
            Dinosaur | Oct 30, 2009 05:51am | #23

            And on that note, I am soooooo outta here....

            Dinosaur

            How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....

          8. mike_maines | Oct 30, 2009 12:54am | #17

            "Please" does not excuse name calling.  Please edit your post.

          9. User avater
            Dinosaur | Oct 30, 2009 05:01am | #19

            From: 

            Mike_Maines <!----> View Image<!----> 

            5:54 pm 

            To: 

            excaliber32 <!----><!---->unread

             

             

             

            "Please" does not excuse name calling.  Please edit your post.

            ---------------------------------------------------

            Thanks, Mike, but it ain't worth worrying about. Why should I care what a linguistically-challenged individual with delusions of vocabulary misspells in my direction? ;o)

            Dinosaur

            How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....

          10. mike_maines | Oct 30, 2009 05:51am | #22

            LOL, I didn't figure you'd take offense, but it's pretty blatent name-calling (mispelled as it is) and we're getting hammered for not being "consistent"--so, just trying to be consistent ;-) 

        2. mike_maines | Oct 30, 2009 12:53am | #16

          Nothing wrong with calling the beams he's describing "girders."  It's a common term for a beam that supports joists.  Often shortened to "girt" in timber framing.

  2. DanH | Oct 29, 2009 07:34pm | #3

    I don't have a lot of experience in this area, but in my limited experience houses can take a lot more than you'd expect. The key is to go "slow" (with "slow" being anywhere from 1/8" to 1/2" a day, depending on gut feel and how far you need to go total). You may crack some plaster (but surprisingly less than one would expect), but the "bones" will take it, so long as they're reasonably sound to begin with.

    A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
  3. Hudson Valley Carpenter | Oct 29, 2009 07:36pm | #4

    The new roof is on the old addition, most of the plaster is down, and now we move to the basement and secure it.

    WTF???

    Dear Mr. X,  Your ability to obscure the issue is Xceptional.  How about some photos?

    1. excaliber32 | Oct 29, 2009 09:33pm | #7

      No camera to post, or I would be glad to. I post these questions hoping someone has had similar experiences, and might could offer a little advice. I've done alot of this kind of stuff before, but at a much smaller scale. This job has sent more than one contractor running for the hills!

  4. User avater
    Jeff_Clarke | Oct 29, 2009 09:14pm | #6

    I have a lot of experience in this area, so the first question is what exactly do you mean by old?

    In most cases, 18th century hewn beams take a 'set' over time and should not be jacked, but rather sistered level.  Especially if they are oak.   Otherwise you tend to lift the ends as well - the whole enchilada - and that makes for a real mess.

    Now if by 'old' you mean 1950 - well nevermind.   1850?  I might jack.  1750?  No way.

    Jeff

    1. excaliber32 | Oct 29, 2009 09:41pm | #9

      The house is about ninety years old. Alot of mold covering them, but I belive the girder "thingies" to be pine. I've considered sistering more than once. I'm dealing with actual thicknesses here, so I may just buy one size up and rip it down. There is significant sagging, especially around the "new" stairwell. I don't necessarilly think it was the stairwell itself that caused the problem, however. I think that once the piers finally washed out, the load shifted that way. There are some flying splices between the girders and the foundation that concern me a little, but I think the majority of the problem is the bad piers and spaced columns (screw jacks about ten feet apart).

  5. frenchy | Oct 29, 2009 10:29pm | #12

    Wood is remarkably flexible  if you have sufficent jacking strength to push them up past level  chances are if the wood isn't rotted it will flex back.  To be safe don't jack it more than about an inch a day..I've done more but sweated it a lot..

     Remember to go past level to allow for some settling..

    1. excaliber32 | Oct 29, 2009 11:26pm | #14

      Two twenty ton jacks will be sufficient, I think. The upstairs was converted into an apartment, so there will be quite a bit of weight. We are pouring pads before jacking and setting simpson post bases in the 'crete. The old screw jacks gave up along time ago. Most of them are still plumb, but they are spaced far apart (about ten feet or more) and at least one of them is bent up pretty bad. I thought at first it was the flying splice that was causing the problem. The beams/girders are roughly six feet apart and at one time had full lenght joists between them. The old carpenters spliced onto the joists to get them the rest of the way to the foundation (joists are about 24" o.c. +/-). The splice landed on the beam most of the time, but sometimes not. With a full lenght joist between beams, I'm sure it wasn't a problem. Then some "super builder" cuts into about ten of them to add a stairwell. Most of the joist sagging is around that stairwell, which is also dead-center of both girders. I think it all held up fine until the piers washed out. (I think it was all crawl-space at one point. Someone dug out a pit roughly 20'x20' x5' for a basement. The screw post jacks aren't original either). The girders have one pier about 2' high until the basement pit where there are those screw jacks. Its the same on both sides.

      We aren't trying to get dead-nutz level here. We just want to get the obvious droop out of the first floor. I'd say from beam to foundation, the 2x8 (actual) floor joists span sixteen feet (we won't get accurate measurements until tommorrow or the next day). I don't have my chart in front of me, but I'm thinking another set of girders mid span on both sides may not be out of the question.

      I'm just a little concerned about jacking those old timbers. I think when I first got there weeks ago, I was finding at least an inch to inch and a half of settling with a six foot level. By the way, the old girders are joined with a half-lap joint.

      Edited 10/29/2009 4:29 pm ET by excaliber32

      1. DanH | Oct 30, 2009 01:51am | #18

        In a two story structure of some age you need to be aware that making the first floor level may make the second floor unlevel. You want to check both and try for a happy medium (or at least a contented psychic).
        A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter

      2. frenchy | Oct 31, 2009 02:36am | #24

        I've had to use as much as a 50Ton jack to raise some beamsin the past with additional stories sitting on them.

         I've seen even 50T jacks defeated if the load is great enough like trying to raise the loft in a barn..

          But an inch a day has never been a problem if the timbers are sound..

          You mention that the timbers are joined in a scarf joint?  Hopefully at the point of the scarf you are putting a support column.

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