Wood truss repair fame

[ayespy]

After six years in a wide range of construction fields and 25 years out of construction, I'm adding a 2nd floor to my house. I've framed it and am ready to roll roof trusses. Truss company delivered 2/12 single-pitch trusses for roof, and two turned out to be just about exactly 2 feet short (16' instead of 18'). Truss designer admitted his mistake and ordered repair frames, which arrived on site today.

I'v never used repair frames before. They're just about 6' long, overlapping the "too short" trusses by 4'. My natural inclination would be to face-nail the overlapping sections together and then add a 2x4 scab to the side of the repair frame along the top chord for the last two feet to extend the line of the original truss and provide backing at my sheathing seam.

Am I talking thorugh my hat here?

 

[boo1]

The truses should come with there own repair plan including attachment methods, check the truss sheet. But your plan looks good.

 

[ayespy]

Thanks for the feedback. Finally got ahold of a structural engineer friend of mine in his 80's, and asked him, too. He agreed - with the caveat that I ought to use 10d nails @ 6" staggered, and glue as well. 8d nails too little penetration and 16d nails too likely to split the chords. Properly done, the glue should pretty much transfer load %, effectively taking the nails out of the equation.

Interestingly, he has not run into this before, in spite of over 50 years structural and forensic practice, and having designed some of the landmarks in our town.

Checked my 33 pages of calcs and drawings, like you suggested, and they are generic, only specifying a repair for floor trusses, and not gable or mono (like mine) roof trusses. I will call the designer in the AM and see if he has specs for this. Anyone who has actually done this in the field is more than welcome to chime in...

Thanks again.

 

[boo1]

I have done a few truss repair in the field but never like yours. (I would have sent the trusses back!) Typically with glued joint the nails only act to hold the joint togther till the glue dries and transfer the shear load. For the scab use SYP #2. Install the nails in a row of two @ 6" OC.

 

[ayespy]

Thanks, boo1.

Seems this truss company uses a sub do make repair frames, and expected the sub to deliver my wets. I got them faxed, and the repair notes are exactly as you and I figured, minus glue, but with the 10d nails @ 3" o.c. (same as two lines on 6". Thanks again. Looks like I'm good to go. I'm still using glue.

 

[sgc]

Greetings,
As per the above truss concerns, I want to know what kind of glue should you use on the face of those trusses?

THanks,
J.

 

[ayespy]

I used a heavy solvent-based general construction adhesive available at my local hardware in tubes for application with a caulking gun.

 

[boo1]

Using an AFG-01 rated construction adhesive will provide a better joint. These adhesives are readily available at home improvement stores and can usually be located by asking for “sub-floor adhesives.”

 

[ayespy]

I shooda specified. Liquid Nails(r) for Subfloors and Heavy Duty Construction Projects is what I used. Exceeds APA AFG-01 and ASTM D-3498 standards. Orco builders supply also disributes their own "Pro-Series" brand of a similar adhesive, which I've used, but I find that the Liquid Nails(r) is easier to dispense and goes on smoother.

There are others...

The reason for an AFG-01 adhesive is that it remains "permanently" flexible but very hard, and so is less likely to have the bond broken by bending and twisting moments - and so is better under wind and seismic loads than an adhesive which dries brittle or frangible. A good one will exceed 450 PSI shear reistance, bridge gaps of a cm or better, etc.

boo1, you are 'way too attentive ;^) - thanks for clearing that up.

 

[boo1]

I have used liguid nails too. But I have been reluctant to include the additional resistance in my calculations (out of ignorance). Cheers

 

[bylar]

Interesting that all the replys are from other than strctural.

By

 

[boo1]

Yes bylar, I guess the structural guys like steel better than Wood!