Site built truss placement

Started by rayian, March 25, 2016, 01:30:32 PM

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rayian

I'm wondering how to place the site built trusses as in the 20x30 1 1/2 story. Since there's no birds mouth how do I assure that they are correctly aligned so that the roof will be flat.

Redoverfarm

Quote from: rayian on March 25, 2016, 01:30:32 PM
I'm wondering how to place the site built trusses as in the 20x30 1 1/2 story. Since there's no birds mouth how do I assure that they are correctly aligned so that the roof will be flat.

Not completely following you. Regardless of whether they are manufactured or home made truss should not make a difference.  If the ridge is level and aligned and the top plate is level then the roof should be level.  Lay out is the key both at the ridge and the plate.


rayian

The site built trusses are 45 degrees where they meet the top plate. There's no flat section as with regular trusses where the ceiling joist section sits flat on the top plate. So, if you place one side of the truss slightly high the other side will be slightly low and therefore slight variations from truss to truss will cause a ripple or wave along the length of the roof. Just wondering if anyone has a good method to assure they are constant.

Redoverfarm

Quote from: rayian on March 25, 2016, 07:48:32 PM
The site built trusses are 45 degrees where they meet the top plate. There's no flat section as with regular trusses where the ceiling joist section sits flat on the top plate. So, if you place one side of the truss slightly high the other side will be slightly low and therefore slight variations from truss to truss will cause a ripple or wave along the length of the roof. Just wondering if anyone has a good method to assure they are constant.

Most truss will have the bottom cord or ceiling joist that rest on the top wall plate and then the gusset will be directly over the wall plate for the top or rafter cord.  Assembling them usually requires a "jig" to make sure that they are assembled with the same dimensions to get them all to be the same. 

ChugiakTinkerer

A picture of your truss will probably help.  If you don't have a flat edge of the truss bearing on the top plate you'll have a hard time supporting the weight of the roof.

Back in the day I always ran a length of string along the truss ends, making sure they were all flush to the string along one wall's overhang.   As long as the part of the truss that rests on the wall is flat then any variation in wall position will not affect the flatness of the roof.  If you don't have that flat edge then any imperfection in the wall will result in a dip or bump in the roof surface.  If the truss you describe is as I'm understanding it, you'll probably want to add a scarf piece to act as a bearing surface.
My cabin build thread: Alaskan remote 16x28 1.5 story