Log Home Design

[CBSE]

I ran a search on here for log home design and there really hasn't been much since 2006-2010.

I recently was asked to design my first log home. Standard D-log construction. I have designed a lot of custom homes, but not log specific homes. Where does one start with the lateral on this and also standard details? It doesn't seem like it would be difficult, but what happens if I need a hold-down at the end of the wall? Is there a tie rod system with a spring that goes from the top of the wall to the foundation that runs through all of the logs at the edge of the opening? I'm assuming the walls can only be analyzed as segmented shear walls. How do the logs resist out of plane loading without buckling? These things look like a hinge joint factory.

For connecting the logs together to resist lateral forces, is it as easy as looking at the shear transfer between the logs and specifying lag screws connecting each row of logs together (1/4" x 12" lag screws @ 24" o.c or something like that?)? I'm assuming that once you get your lateral load on a wall segment that the screw pattern from the top log to the bottom log has to be the same.

For connecting to the foundation, there would have to be a 2x pressure treated plate with anchor bolts. Do the anchor bolts go through the first coarse of logs?

There really isn't much out there for design standards. I found the ICC400 and it has some okay information, but is more of a prescriptive method, or so it appears.

Thanks!

 

[XR250]

The out-of-plane stuff - especially near big windows and doors is what keeps me from getting near these things.
Hinge joint factory is a nice way to put it.

 

[CBSE]

Yes, that is what makes me really nervous. Even where there aren't windows but there are large point loads or large uniform wall loads it seems that the buckling effect would be very severe.

 

[XR250]

Buckling and just simply weak axis bending due to out-of-plane wind.

 

[oldestguy]

Why don't you make a phone call to someone that builds log homes, say out of your area where you are not a customer?
I lived in one and added onto it myself. They were something like 8" by 12".

It was regular logs squared off some. They were laid with two spongy weather strips between. Every 2 feet along the log at right then left side a 1" diam. hole was drilled half way into the log. A 12" long spike was nailed between top ad lower log. 1"diameter holes were drilled before laying to accommodate the wiring that was to some along. I made several "jigs" of 1" diam rod, a few inches long with a large washer was welded near one end that was sharpened. Set them in the top of the lower log and drop the upper log into place to mark the place to drill in that upper log. Double check that these holes line up before doing the nailing.

At doors and windows, before setting windows and door frames, use a heavy square steel section, say 1-14/" x 1-1/4", inlet into that bunch of exposed logs. Cut the notch with a skill saw and a router. Allow for shrinkage of as much as 2" per 8 ft wall height at windows and doors.

I had an Amish crew helping and really had a mess when a spike wad dropped into an electric line hole instead of where it belonged. Took some doing to get that spike back up.

Had no problem tying the eaves together by making use of the flooring "joists" in the second floor as tension members and appropriate brackets either bought or made up.

You can bury wiring and cables in the "joists" in a channel routed out on top, but don't drive any nails into electric cables there. It is hard to remember which one has them, so a written plan should be made up.

Do plenty of planning on the wiring because later it is not easy to add any outlets.

With the spiked logs I never had any problem for 20 years there and many nearby log holes also none.

 

[Guastavino]

Cynicism and snarkyness aside. I would hazard a guess that Log cabins are more often just built, than structurally designed.

So how does that help this thread? I would say it does because ANY effort on the engineering front is likely better than the "standard practice" of local professionals under similar circumstances, IE legal framework for a defense if something went awry.

Also, Contact woodworks. They likely have some great resources and their advice is free to you (Wood vendors help pay for their services)

 

[msquared48]

You can also get ahold of "The Log Builders Association" in Canada for some additional information.

These are not structures that have to be specially detailed and tend to be manufacture method controlled (Joinery used) as to how the analysis should take place. Lateral shear, and bearing mechanisms, vary from manufacturing style to manufacturing style. Controlling settlement is the biggest issue, next to short wall lateral stability.

Mike McCann, PE, SE (WA)

 

[CBSE]

Does anyone have any example drawings that they could share?

I'm thinking I'm getting a little more comfortable with the openings. Basically, I'm looking at requiring continuous logs across openings that tie into either a return corner or an additional vertical log to transfer loads. Does this sound logical?

 

[XR250]

Logical, but will probably be met with resistance from the supplier.

 

[oldestguy]

Why not take the time to go and visit areas where there are log homes? I'm sure most any owner would gladly "show off" their happy home. Even checking with the builder might help, especially if he might get the job of building your project.

 

[CBSE]

I'm about 3 hours away from anything new or extravagant. Log homes are not that common in my area. It's a great idea, and I may end up doing it, but it makes it difficult to balance the trip and other work loads in the company.

 

[TLHS]

http://www.logassociation.org/resources/publications.php

https://law.resource.org/pub/us/code/ibr/icc.400.2007.pdf