Stacked Log Header Where Logs are too Short
Stacked Log Header Where Logs are too Short
(OP)
Ok I will start by disclosing that this is my first post. I been a member for a short while now. I looked in the other post before asking the following question.
I have a friend that has come to me for some help. He is building a log home in CA and the logs that showed up on site are to short (16') to span the required (18.25') garage header. My first thought and analysis was to create a composite beam out of the three log lifts that will stack above the opening. I had planed on securing the three stacks together with through bolts or threaded rod at calculated spacings based on the simple span shear and the local horizontal shear per unit length at the connection of the outer stacked member. My only hang up with this analysis is am not clear if there is any structural disadvantage to not having a single one of the three stacked logs span the full opening length. As a composite beam, with logs butting end to end and stacked with the joints staggering, the header will span. Is there any thing I am missing with this analysis, do I need to include a hing at the location where the logs butt together over the opening?
Images Should be attached if I did it correctly. Thanks in advance.

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I have a friend that has come to me for some help. He is building a log home in CA and the logs that showed up on site are to short (16') to span the required (18.25') garage header. My first thought and analysis was to create a composite beam out of the three log lifts that will stack above the opening. I had planed on securing the three stacks together with through bolts or threaded rod at calculated spacings based on the simple span shear and the local horizontal shear per unit length at the connection of the outer stacked member. My only hang up with this analysis is am not clear if there is any structural disadvantage to not having a single one of the three stacked logs span the full opening length. As a composite beam, with logs butting end to end and stacked with the joints staggering, the header will span. Is there any thing I am missing with this analysis, do I need to include a hing at the location where the logs butt together over the opening?
Images Should be attached if I did it correctly. Thanks in advance.

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RE: Stacked Log Header Where Logs are too Short
Mike McCann
MMC Engineering
RE: Stacked Log Header Where Logs are too Short
Thank you for your response. I believe a request for the proper length logs have been made to the manufacture but this request has been met with heavy resistance. Partially due to the case that the manufacture is have way across the country. I am just trying to come up with a alternative solution for the owner/builder. I have come up with two possible remedies to the short log lengths. The first is that presented above, which utilizes already purchased materials. The second is to design the header using a glue-lam and face the header with a fascia from the short logs. I would like to exhaust the first before recommending the second. Oh and the logs are a classic 8x8 "D" shape similar to PanaBode.
Thanks,
RE: Stacked Log Header Where Logs are too Short
Honestly if this is a pre-manufactured building then who cares about resistance, they either provide the proper materials, or engineer a solution themselves and get their engineer to sign off on it.
If you cannot get the proper length pieces then remedy two is definitely the way to go over coming up with some way of load transfer using bolts without a continuous member.
RE: Stacked Log Header Where Logs are too Short
RE: Stacked Log Header Where Logs are too Short
Am I mistaken in my thoughts that a gluelam beam is just an engineered composite beam? Is it not created from individual planks that are of varying lengths (some not spanning the full length)? So looking at a composite beam/header of 3 logs mechanically connected in a way using threaded rods to resist the local horizontal shear acting on each connecting face of the three logs, is it any deferent than using a glulam? I have not been involved or studied the properties of glulam or engineered composite beam construction. At this point I am just wondering if the application and engineering principle is the same? In my current situation I plan to recommend replacing the headers with a gluelam, or force the manufacture to provide the proper material. I just would like to close the loop on my composite beam theory.
RE: Stacked Log Header Where Logs are too Short
Just push the issue and wait for the longer sticks. You will be happier in the long run.
Mike McCann
MMC Engineering
RE: Stacked Log Header Where Logs are too Short
And even as I continue to think about how to do what you were proposing I still cannot come up with a detail that I'm comfortable with.
RE: Stacked Log Header Where Logs are too Short
GlueLams are made under pretty rigorous shop control, and they won’t usually have butt joints in the outer couple plys in regions of max. normal bending stress, or max. shear. The outer couple plys will also usually be of a better tensile grade than the inner plys. Many times the butt joints are finger jointed, and seldom (never) fail at that finger joint. And, you just can’t duplicate this quality control, grading and gluing with the logs, out in the field. Otherwise your thinking about GlueLams is about right, most good wood design text books cover the theory behind their manufacturing and use. Through bolts alone won’t work will, because they have to move too much in their holes before they really come into bearing on the holes; meaning much slip in the two horiz. joints and much deflection of the header. And, the bolts will loosen as the logs shrink. I think your best bet would be the GlueLam for the header, and rip some slabs to cover the outside face. It can be an industrial grade GlueLam, rather than an Arch. appearance grade. I can imagine several ways your three log header might work, but they are probably more work than they are worth.
RE: Stacked Log Header Where Logs are too Short
RE: Stacked Log Header Where Logs are too Short
Thanks for your input. I will explore the GlueLam header over both openings.
You all have been vary helpful.
RE: Stacked Log Header Where Logs are too Short
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: Stacked Log Header Where Logs are too Short
RE: Stacked Log Header Where Logs are too Short
The contract plans for this structure as some of the most lacking I have yet to see. The plans and permit for this structure were done in 2008 and lack in my opinion lots of information that a good builder would need. There was some miscommunication between the structure designer and the log manufacture (not the same entity). The log manufacture only mills "D" logs in 14' and 18" lengths. Designed clear opening was 18.25' oops...
cvg
I do not wish to redesign any structure. I am merely trying to be a resource. as it stands of now, the owner/builder is contacting the manufacture of the logs, (structure designer has since past away, making things more complicated) to have them supply a design for a full length header beam over the opening. He is also pushing them to cover the cost of the beam and delivery fee. We shall see how this will pan out. I am interested to see how they come up with a positive attachment to the log walls, I would assume a vertically bolted connection at each end with a horizontal strap on top of the header. We shall see.
RE: Stacked Log Header Where Logs are too Short
Another considerations, most prefabricated assemblies come with some kind of insurance/warranty period. Is it possible that after you provide your "fix", that the manufacturer considers that grounds for voiding the warranty? I know you are just trying to be a resource, I would be too, but in 2 years when there is another problem, will you have just created more trouble for your friend?
PE, SE
Eastern United States
"If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death!"
~Code of Hammurabi