splicing 2x12's to get longer member
splicing 2x12's to get longer member
(OP)
I am considering splicing (2) 2x12's together in order to get a longer rafter, but also get the bending strength of a double rafter. 24' is the typical stocked length in our area and I have a roof that has a 25' span. The dead and snow loads require 2x12 DF2 @ 12" o.c. I would like to splice (2) 24' pieces together with 1' offset at each end and set them 24" o.c. I believe with the right nailing (about (4) 10d @ 12" o.c.) and some glue for safety, this should function well as a double 2x12. The max shear load is plenty for a single 2x12 and this allows me to use single 2x12 hangers at the ridge. Does anyone have any major objections or am i missing something? We save a lot of money and lead time for specialty lumber.
Thanks
Thanks





RE: splicing 2x12's to get longer member
Mike McCann, PE, SE (WA)
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
your 24' foot long 2x12 may be finger spliced to begin with. splices are not always bad but can be. make sure you use exterior grade glue and fasteners that cannot rust out. the problem is those nails and glue are far more critical than anything else.
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
http://www.fpl.fs.fed.us/documnts/fplrp/fplrp333.p...
IMHO, if the two members are properly bonded over the 23 foot overlap (which should be pretty easy to do considering the length) then the splice in not a problem.
Likewise, since the one foot length of single 2 x 12 at each end is adequate for shear this is not a problem either. In principle, this is not much different than coping of a steel beam at the connections... and that's done all the time.
I agree with dcarr82775 that the glue is most important; don't cut skimp on that.
Additionally, the span to depth ratio of the beam is very high, 26.7 (i.e. 300" / 11.25"). It is asking a lot of a simply supported beam of any material to perform well with that slenderness. Be sure to recheck to make sure deflection is ok.
Finally, I suggest that you pick the "best" end of each individual member to at the end of the beam. You want the best wood there to carry the shear load.
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RE: splicing 2x12's to get longer member
To everyone else, please know that I am certainly appreciative of your time trying to get me to think out of the box. I was just growing a little impatient since I have deeply considered all of the options, spent time on the phone with the supplier & framer, and just needed to discuss the technical merits of my actual question.
Keeping it simple was the 2 options I had put on the plan. We were beyond that.
And for the record, TJI's suck for sloped roofs that don't have full depth tails.
Thank you all for being a great resource for one-man engineering operations to bounce ideas off of.
RE: splicing 2x12's to get longer member
Don't trust a nail or nail gun, bult clamp the two together with 5/16 or 3/8 bolts and washers, both sides.
Offset your joints with the through spans:
For a 24 foot-long joist, use 6 ft + 12 ft + 6 ft spans on one side of the joint. 12 ft + 12 ft on the other mating 2x12 joist.
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: splicing 2x12's to get longer member
I would make damn sure that the members are blocked out at the supports (as I'm sure you would do), but I would also provide blocking as if this 25' length was spanned by a 2x12 member rather than a 2-2x12. I hope you see what I mean...
RE: splicing 2x12's to get longer member
Good advice, but I think what you are referring to were compression braces, not bending members.
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
I would prevent rotation in the system to not allow any "surprises" in this very long lap joint or the bearings.
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
RE: splicing 2x12's to get longer member
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.