Longitudinal Split in wood
Longitudinal Split in wood
(OP)
Hi All -
I have inspected an attic with wood trusses. It was built 40-years ago. I found numerous number of split members. The members are in both tension members and compression members. I could not identify a pattern. They are random. This image represents the type of cracks I found.
I did a quick analysis of the truss and found it to be fine (4/12 Fink truss spans 28').
What could the cause of suck split be?
Thanks in advance.
I have inspected an attic with wood trusses. It was built 40-years ago. I found numerous number of split members. The members are in both tension members and compression members. I could not identify a pattern. They are random. This image represents the type of cracks I found.

I did a quick analysis of the truss and found it to be fine (4/12 Fink truss spans 28').
What could the cause of suck split be?
Thanks in advance.
RE: Longitudinal Split in wood
RE: Longitudinal Split in wood
RE: Longitudinal Split in wood
RE: Longitudinal Split in wood
I agree with Eric C., looks like pith, i.e. the center of the tree. If a crack does not propagate thru the thickness of the member, across the member. It is usually not significant.
Jim
RE: Longitudinal Split in wood
While it looks terrible, checking does NOT affect the flexural strength of a member. It does affect the shear strength. If you look at the 1991 or 1997 NDS there should be a factor to INCREASE the shear strength of beams that do NOT have checks like this. Sort of a backwards way of doing it.
The newer NDS codes, I believe, do NOT have this factor. But, from a first principals standpoint it could still be applied.... Long complicated story about why the codes essentially doubled the shear capacity for all wood beams.
I'm not certain about whether it affects tensile or compressive strength. But, if my memory is correct, I don't think it does. Though intuitively I would think it would affect the tensile strength.
RE: Longitudinal Split in wood
RE: Longitudinal Split in wood
If it's a small member 2x4 2x6 or such, then that type of checking / splits would be pretty odd. And, it does look like lower grade wood. Maybe worth doubling up the members that are split like this, though I don't want to nail into them much in fear that it'll split more. Anyone use adhesives to double up a damaged member like this?
RE: Longitudinal Split in wood
JoshPlum, if you are trying to justify adding a member alongside, my suggestion would be to use a structural epoxy. My experience in the wood product manufacturing industry is that standard construction adhesive simply is not effective enough on wood to wood connections to develop appropriate load sharing. Not sure I agree that it would be as simple as sistering a new chord alongside this truss chord, however.
RE: Longitudinal Split in wood
Mike McCann, PE, SE (WA, HI)