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Log Sizing for Cabin

Started by Buckshot1822, August 06, 2019, 10:02:31 PM

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Buckshot1822

Hello, this is my first post but I have been here on and off for a few years reading info.

I am planning on building around a 25x40 hunting camp in the next year or two. It will more than likely be a slab on grade, and likely have an epoxy coated floor for easy cleanup. We are interested in a log structure, and do have a little bit of experience amoung us with log construction. Our group has a lot of construction experience in general.

My question has to deal with milled log sizes. Right now we are looking at some 4x6 H logs, because we found a really good deal on a lot of them. Enough to build 25x40 and one inside partition wall from them and still have alot left over.

Would there be any issues from a structural standpoint with these logs for say a 10' wall height? We would use log screws and more than likely glue. Our roof would probably utilize prefab trusses fwiw.

Obviously 4" doesn't give you a lot of R value, but we shouldnt really have any issues with heating / cooling, it will not be continuously occupied for any length of time.

I cant forsee any structural issues with a 4x6 log properly installed, but I'm interested in seeing what others opinions are.

Don P

When it's that thin I would consider it more as a type of siding to be attached to a frame of some sort at relatively frequent intervals. just shooting from the hip I would want something to act as a column element every 8-10' along the walls to keep the walls from bowing in or out under roof load. Or for that matter use them as infill between heavier posts that actually support the loads.

barbender

Like Don said, long, tall log walls need lateral support, probably best done with intersecting log walls, in addition to your screws or dowels. Also, even though you are using milled timbers, the wall will still settle considerably. With full round, scribed logs you figure 3/4" per foot of height iirc. I don't know what the figure is for milled logs (depends on if they are dry, etc), only that it will be enough that you need to factor it in around doors, windows, and anything that goes through the roof. Basically anything that is at a fixed height needs to be able to have the logs slide past it.
Too many irons in the fire

rjwoelk

I like the idea of infill. 8x8 posts on a timberframe . We used 8x10 on the cabin.  
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firefighter ontheside

I don't see a problem with them holding the weight, but as said the main concern is lateral support.  You can have intersecting interior walls or just T's creating a column of sorts every so often.  You can determine the moisture content currently and roughly calculate the shrinkage as it dries further.
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Buckshot1822

The wood should have a pretty low moisture content. They are around 5 years old and have been kept inside the entire time.

We will have one wall that will be perpendicular to the 40 foot walls somewhere around 1/3 of the building.

Don P

Settlement will be pretty much nil if you get them tight. Keep an eye on it, if you see the wall bowing or if it flexes in the wind attach a post to it and secure it every few feet. I've attached a flattened tree to the interior of one for that purpose. You are actually pushing the limits for a stick framed wall as far as distance from a bracing wall and are considerably less strong in the buckling direction.

A little feedback on settlement, the big 2 crib log barn we worked on 2 years ago has 18' tall log walls surrounded by timberframe sheds. We harvested and slabbed 2 faces to 9" width as the builder notched and built. We checked moisture content a few weeks ago and decided to jack and level it. The poplar logs are at around 18%. The bottom couple of rows are white oak, still at around 30%. The builder assumed 8" of settlement, I think it is about done, we lifted it 4-1/2".

Buckshot1822

Just as a follow up, we ended up buying the logs, and are trying to come up with some building plans.

We will be around 25x40 with roughly an 8'8" wall height.

I am open to suggestions about stabilizing the walls. My current thoughts are 6x6 posts on the interior anchored to the slab with timberlinx fasteners or something similar. There will be one partition wall around 15 feet on the 40 foot side. We will use the 4x6 logs to construct that wall and may interlace it with the exterior walls. That will leave 2 rooms, basically 15x25 and 25x25.

Any suggestions are welcome.

Don P

I don't know enough about your plans, and probably don't know enough to answer your question directly but a few things to think about as you design. The rafters on any house need to be tied across their heels by ceiling joists or some form of tie to prevent them thrusting on the walls, or, the rafters need to hang from a structural ridgebeam to remove that spreading thrust on the walls. Then the problem of tall thin walls buckling. A common rule of thumb, a post that is 1" thick for each foot of height will not fail by buckling, it will crush before it buckles, so for instance typically an 8x8 post 8' tall does not need to be checked for buckling.

Stephen1

It has been mentioned about supporting for bow, I always remember reading about log walls over 20' in length need a "t" a "wall" So at 25' of wall I would be concerned.
I modified from 15-25'
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TW

In my part of the world the traditional log building method uses logs sawn or hewn on inside and outside with the live edges scribe fitted together using a long groove. Plenty of 1 1/2 inch pegs are used around openings.

A 5 or 6 inch wall is considered stable up to around 7 metres (23 feet) in lenght. With full lenght good quality logs above and below window openings one can push the limit a bit further but that's maybe a metre or so.
This is all under the condition that there are ceiling joists dovetailed in to hold the upper part of the wall stable and that there is no outward pressure from the roof.
Even longer free standing scribed walls are indeed possible. At least 10 metres (33 feet) if you use 6 inch logs and stabilize them with vertical logs bolted to the wall at let's say 3 metre (10 feet) intervals. The bolt holes in the veticals are elongated to allow the wall to settle.
Even longer free standing walls can be built using what we call a "blockkista" in Swedish. That is a small log built "box" built either on the outside or the inside of the wall. Found in old churches for instance.

I would not dare to build 24 foot long walls with 4 inch logs. Particularly not if the logs don't have a proper long groove to stabilize them. Definitely not if the logs are just held in place using screws or if there are no full lenght logs.

cabindoc

Quote from: Buckshot1822 on August 06, 2019, 10:02:31 PM
Hello, this is my first post but I have been here on and off for a few years reading info.

I am planning on building around a 25x40 hunting camp in the next year or two. It will more than likely be a slab on grade, and likely have an epoxy coated floor for easy cleanup. We are interested in a log structure, and do have a little bit of experience amoung us with log construction. Our group has a lot of construction experience in general.

My question has to deal with milled log sizes. Right now we are looking at some 4x6 H logs, because we found a really good deal on a lot of them. Enough to build 25x40 and one inside partition wall from them and still have alot left over.

Would there be any issues from a structural standpoint with these logs for say a 10' wall height? We would use log screws and more than likely glue. Our roof would probably utilize prefab trusses fwiw.

Obviously 4" doesn't give you a lot of R value, but we shouldnt really have any issues with heating / cooling, it will not be continuously occupied for any length of time.

I cant forsee any structural issues with a 4x6 log properly installed, but I'm interested in seeing what others opinions are.
I know this was awhile that you posted this, but in the advent you have not yet assembled or completed said project, I have some advice.  I have been called in to repair bowing walls on larger logs, so here is my .02
1 Don't glue anything.  Logs of any size move.  Daily and seasonally.
2  Shrinkage is not something you need to be concerned with.  2-3 years and that's over with.
3  Use bigger logs/timbers for wall ties and/or wall stiffeners.  
4  Use 2x4 for interior walls.  Makes for easier electrical.
5  Wall stiffener every 8-10' lag bolted to interior log walls every 3' from floor to ceiling. 
6  This should be at lease 3x8, 4x4 or 4x6  bigger is better. If you need an empty chase, you can do a box of 2x6, but       not all of them.
7  If corners interlock, no need for anything there.  when stacking logs, stand 4x4's in the corners plumb.  helps to keep a reference line as you move up.
8  Wall ties, if your not doing trusses
9  I would use 5/16 lags and washers over timber screws.
Best of luck, post completed pics.
Scott  aka cabindoc  aka logologist at large
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