out of plumb log cabin walls 1

[DZNC]

I am reviewing an old log cabin home in coastal NC. One of the walls is out of plumb by 3 to 4 inches over 8 feet. I believe it is 7 or 8 inch logs. Does anyone know of acceptable tolerances or ways to determine if this is a concern?

 

[LittleInch]

If it's still standing and not leaking it sounds acceptable to me...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[phamENG]

DZNC - what caused it to be out of plumb? Was it built that way? Are the logs still interlocking? You say old - is it actually an old log cabin (built by hand from locally cut trees) or a kit log home from the 70s?

There are no standards or tolerances for historic log structures that I'm aware of. It's a matter of engineering judgment to determine why it's out, what that could mean, and if it's a problem.

 

[DZNC]

Thanks you @phamENG and @LittleInch

It appears to be built out of plumb and the posts themselves have a pretty decent bow to them. The logs are still interlocking though. This is an old log cabin built by hand from locally cut trees.

 

[phamENG]

Can you post some pictures? I'd be interested in seeing what you mean.

Log cabins tend to be pretty robust structures if built properly. Provided the water and pests are kept out, they can last a really long time. Some creep in loft floors could cause some issues where the logs were cut, split, and installed green.

 

[BAretired]

If it's still standing and not leaking it sounds acceptable to me...

That is not an adequate criteria for acceptability. It should be reviewed by someone experienced in this type of construction.



BA

 

[DZNC]

 

[XR250]

How do you even get the numbers to work out on one of these?
Depending on the wall layout, you are counting on stacked horizontal logs spanning vertically.
Where does the "weak axis" strength of the assembly come from?

 

[phamENG]

How about a picture of the corner? That doesn't look like a typical log cabin - that looks like a post and beam with log infill.

XR - for out of plane loading, think about a pole barn with 2x4 or 2x6 girts at 4' on center with poles every 4' to 6'. In a small cabin, the logs often span the entire width of the wall. In longer ones, they may need to do a butt splice. Either way, as long as you can justify a "continuous" log through splices every 4th log, you have an effective 8"+ girt every 3-4 feet or so. How much further can it span than the 2x6 girt?. As things get larger and more modern, you have to start hiding connections inside the logs to tie them together more reliably.

 

[Enable]

I agree with phamENG seems like quite a few discontinuities to really be a true log cabin. Look at the division right at the edge of the drop ceiling. That would be some odd no-purpose trim for one where the logs are intended to span the entire wall. Though I've only ever seen a few and designed none, so. Take that with a grain (mountain) of salt!

Also, how are you measuring the out of plumbness? Looks like the base may just be baffed but the wall is otherwise decent. Hard to tell from the picture but it doesn't look like a consistent lean. In which case I would think it was built that way, and probably less cause for concern than had it come to that position over time.

Though what really offends me the most here is that someone would pay extra for the log look but then paint over the entire inside in white...honestly, things like that should be a crime!

 

[phamENG]

Yeah, the paint was a mistake. These things aren't really known for their water tightness. So sealing both sides of the logs...you're inviting problems somewhere. Best case scenario the paint starts bubbling and pealing in a year or so - maybe less. Of course they may have used some specialty coating I'm not familiar with. Sort of doubt it, though.

 

[TLHS]

The load path makes this feel more like logs as a series of infill walls that can take shear and vertical load rather than the more traditional style log cabins I've seen where the logs form an integral system.

 

[XR250]

@pham,

Sure that works for small cabins. I look at pretty darn long ones occasionally though with doors and large windows interrupting the "girts".

 

[phamENG]

XR - yeah, that's what I mean by the modern ones. Most of those are built with kits now and have larger structural members hidden in them to achieve the "luxury" fenestration. I haven't seen any of those "in the wild" but researched them a bit as I was working on the design of a traditional cabin last summer. Most of those big ones can barely be called log cabins.

 

[Craig_H]

Having limited log building experience, take what I have to say with somewhat of a grain of salt. I've worked on exactly one project, albeit with a true craftsman of a log builder where I learned a lot.

As some others have alluded to, these look like log infill walls between vertical timber posts - not a true log building. This type of construction is difficult to get right. Log shrinkage perpendicular to grain (as we all know so well) is very real. There are some good details around that allow the log infill portions to be connected to the timber posts for out of plane loads, while allowing for vertical movement of the logs as they shrink. There are also plenty of bad details that have been used over time and that result in the vertical posts carrying both out of plane loads, AND all the gravity loads once the logs dry out and shrink.

The shape of that bowed post looks quite buckle-ey to me. Combine that with what looks like a roof beam above, and my money is on the post being overloaded, and whatever connection exists to the horizontal logs being what is currently holding it from becoming the proverbial moose on roller skates.

 

[DZNC]

Thank you all for the input. There was definitely not enough exposed or known about the members or connections to get too far into any analysis. I let my client know my opinion and that was it. Again, I appreciate the input.