Leveling webbed/engineered floor trusses

Discussion in 'Framing and Foundation' started by diegodog, Jan 8, 2014.

  1. Jan 8, 2014 #1

    diegodog

    diegodog

    diegodog

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    Hello All,

    I am a novice builder who is currently in the middle of building a 60x60 barn (in -30 degree weather UGH). I am currently at the point where I have the floor trusses sitting on the first floor walls (2x6 stick built). The trusses are 24oc and they are 30 ft trusses (I have a double middle wall which holds the interior side of the trusses).

    The trusses are perfectly level if I place the level down the length of the truss. The issue is if I put the level perpendicular to the trusses I have a hot mess. I seem to go from high to low back to high across the trusses as I move the level down the 60 ft span.

    Is there an easy way to determine the high truss? Is there an easy way to get these level beside starting at the high truss and leveling all the trusses from there? I am fairly certain my high points are not on the ends. Any suggestions or tips would be greatly appreciated.

    The only odd thing I have going on is I put a triple top plate on. I am overbuilding due to lack of knowledge. I am fairly certain the cause of this leveling issue is coming from uneven concrete and has worked its way up to where I am now.

    Thanks!
     
  2. Jan 9, 2014 #2

    inspectorD

    inspectorD

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    I would use a string line, that way you can see the high and low and leave the middle ones alone. This is for a wall.. but you get the idea.
    Good luck

    [ame]http://www.youtube.com/watch?v=6iofK-7vmBg[/ame]
     
  3. Jan 9, 2014 #3

    nealtw

    nealtw

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    Welcome to the site:
    As hard as you try concrete can be really hard to get level. We set up a laser and check the height for each stud. So lets start there. Measure up say 2 or 3 feet on the end of each wall. Pull a chaulk line tight and snap a line and all walls. Now check these lines for level. 1/4" with a 4 ft level will be 1 1/4" in twenty feet. Hopefully you will not find a problem the there. If you do lower the high one until you have level and snap a new line. Now go around and measure down from the line to the bottom plate, you are looking for the one that has the greatest distance. Lets say you find that to be 22 5/8 inches, any stud that has a shorter measurement is to high. 1/8" can usually be ignored.
    The tough question is, did you use pre-cut studs or did you cut them yourself? I hope you didn't just put up 8s or 10s just how they came?
    This all worth checking, there is no better time to fix anything that is wrong.
    Some inspectors and engineers frown at the third top plate, something about bend factor. I have seen them call for metal straps to tie them to the studs, not a big deal.
    Let us know what you find..
     
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  4. Jan 9, 2014 #4

    nealtw

    nealtw

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    It must have taken me 17 minutes to answer that one.
     
  5. Jan 9, 2014 #5

    Wuzzat?

    Wuzzat?

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    Since they are level the long way, to make them all equal height you'd need two identical thickness shims at each end of each truss.
    Elevate the two end ones first.

    And decide what is "close enough" to a planar, flat and level surface over these distances. 1/8"?
    You might want to use 3, 5 or 7 string lines because you are leveling a two-dimensional surface.

    Your leveling tools should be at least 5x better than the desired end result. Some of Grainger's levels are advertised as high accuracy and the catalog gives specs. A liquid level/garden hose is probably good to +/- 1/16" over whatever distance you want.
     
    Last edited: Jan 9, 2014
  6. Jan 9, 2014 #6

    GBR

    GBR

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    A string is worthless until you know the attachment points are the same level, check each corner elevation. Laser level, transit level, water level, buy or rent to check corners/mid point at least.

    If snapping a caulk line between marks, keep them at about 15' or the line sags. Or use a rotating laser level, mark the wall at 5' so you don't have to constantly bend over to see high/lows. If in the US, a third plate is fine, even required per code in special instances; http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_6_par016.htm?bu2=undefined I can understand more room for compression but bending... hopefully the wall studs are 16" oc and 2x6 if required per their height;http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_6_par014.htm?bu2=undefined

    Just saw-kerf where the truss sits and remove some material for the tall ones -out of the third plate. I wouldn't shim both ends of truss if only one end (wall below from concrete) is high.......Check with local AHJ.

    Gary
     
  7. Jan 10, 2014 #7

    nealtw

    nealtw

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    Gary: I did explain that he would have to adjust the line to level. Take the sag out of the string. You would be hard pressed to find a sag in a chaulk line that is tight.
    [ame]http://www.youtube.com/watch?v=ACcDtyMwvyc[/ame]
     
  8. Jan 12, 2014 #8

    GBR

    GBR

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    "We set up a laser and check the height for each stud. So lets start there. Measure up say 2 or 3 feet on the end of each wall. Pull a chaulk line tight and snap a line and all walls. Now check these lines for level. 1/4" with a 4 ft level will be 1 1/4" in twenty feet. Hopefully you will not find a problem the there."----------------- if you use a laser level, why would you even need a caulk line. And using the caulk line with a 4' builders bubble level to check the accuracy of a laser level? Extending the caulk line around the building, leveling it as you go.... you confused me.

    Gary
     
  9. Jan 12, 2014 #9

    Wuzzat?

    Wuzzat?

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    If you set up your reference elevation in the center of the 60'x60' square the vertical error to the edges and corners will be minimized but the surface will not be perfectly flat - the center will probably be higher or lower than the edges and corners.
    For +/- 1/4" in 100' laser error the max error at a corner could be 1/8" if I did the geometry correctly.

    If you set up at a corner the surface will be perfectly flat (using a laser) but the elevation in the far corner will be off by more than if you set it up in the center - max 3/16" - so the whole surface will be slightly out of level.

    Probably a perfectly flat surface here is more important than a perfectly level surface.
     
    Last edited: Jan 12, 2014
  10. Jan 14, 2014 #10

    nealtw

    nealtw

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    Gary; We do use a laser, but I don't expect everyone to have one so I went back to the way we did it before lasers and we didn't have a builder lever. You know back when it was a plumb bob and a square or a string level. This is all for knot if the OP dosn't come back with some answers or more questions.
     
  11. Jan 16, 2014 #11

    GBR

    GBR

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    Using a caulk line to extend a 4' level line to 20' is very open for error. Just a sixteenth off in the 4' will give almost 4" in elevation difference in the 240' of building-if dropped 1/16"x 5 (4') each 20'. May work for 20' as you said, only off 5/16" that way, though I would never suggest that procedure to anyone for any elevations- other than something 8'maximum long with a straight-edge and the 4' level. Using a 4' level alone is accurate to 4'. I think the OP is trying to find the high/low ones to plane them all, too late in the ball game to level everything if he never checked the slab before framing began.... could get the bulk out.

    Gary
     
  12. Jan 16, 2014 #12

    nealtw

    nealtw

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    Your laser level is good at one hundred feet to be + - 1/8", unless you paid the big bucks on it, then it's good to + - 1/16. Add to that that your dot woill be more than a 1/4" blob at that distance.
    If you want accuracy you use a builders level (transit) which has two spirit level about 3" long.
    In less than a minute you check the 4 ft level by holding it level on a wall and drawing a level line turn the level end for end and consult the same bubble.

    Now how about you tell me how to check the accuracy of the transit or your laser, we learned the hard way that they do have to be checked.
     
  13. Jan 16, 2014 #13

    Wuzzat?

    Wuzzat?

    Wuzzat?

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    It seems the price paid for a laser level does not correlate very well to accuracy, so user convenience must be the main price driver.
    http://www.grainger.com/search?searchQuery=laser+level
     

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