Finger jointed rafters mid span??

mlefaucheur · April 9, 2015, 9:48pm

I looked at a new construction home today and noticed the rafters had been finger jointed. Is this a common and acceptable practice? Are these just as strong as one solid piece? Please excuse the blurred photo.

rwells4 · April 9, 2015, 10:26pm

If it is a properly engineered truss, then is okay. Has to use approved glue, and glue that is approved has failure temperature higher than that of the burning temperature of the wood. ( a proper truss will/should use proper glue and engineering standards )

https://www.usfa.fema.gov/downloads/pdf/coffee-break/hc-2006-0706.pdf

http://www.carbeck.org/pdfs/060704_Finger_jointed_lumber_Carbeck_Note.pdf?PHPSESSID=cb3v4b53f6svrgur7brqp25611

http://www.nrcresearchpress.com/doi/pdf/10.1139/l83-074

http://www.cwta.net/pdf/FJ%20Lumber%20Truss%20Handling%20Guidelines%20(rev%201-2b)1%20CWTA%20LETTERHEAD%20CORRECTED%20COPY.pdf

mlefaucheur · April 9, 2015, 10:57pm

Great, thanks Robin.

kshepard · April 10, 2015, 2:12pm

That might be true for trusses, but these aren’t trusses, judging from the collar ties. I’ve seen finger jointed studs, but studs are mostly in compression. Rafters are in tension and I would definitely call this one out for approval by an SE unless someone comes up with a link to something convincing.

cevans · April 10, 2015, 3:19pm

I have seen them fail in a similar application and the cost can be huge. I don’t see any grade /manufacturer stamping on them, so I would not assume that they are approved for that use. On new construction, I would advise my client to request the builder’s engineer certify them for that application and document it with his signature and seal.