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General Forestry => General Board => Topic started by: Nsp0005 on December 24, 2018, 11:30:59 PM

Title: Building log cabin with green logs
Post by: Nsp0005 on December 24, 2018, 11:30:59 PM
Hello everyone, Im about to start building a log cabin and would like some advice on what to do. Im going to be building this with green white pine. Has anyone ever used green pine to build something like this? I have a woodmizer saw mill and I will be millling 3 sides to form a D log. My plan is to get log cabin weather strip lay it right down the middle of the logs and culk each side. I then will stack with the butt and pass and apply long screws every two feet and finish by culking the outside and inside. Is this a good plan? What do you all recommend thank you all in advance. 
Title: Re: Building log cabin with green logs
Post by: Andries on December 25, 2018, 12:11:33 AM
There will be a lot of log shrinking and checking. 
- Shrinkage is dealt with a lot of "settling" room above windows, doors and interior walls. Design their frames to use dadoes for the walls to shrink down to their EMC.
- Checking is controlled by ripping a 1 1/2" kerf down the entire kength, on the bottom side of your D shaped log. The checking will localize in that kerf, leaving the log looking Purdy. 
From green logs to final dry can take up to 3 to 5 years; let it happen slowly and the building will behave better than if you close the place up and crank the heat to high. 
Best of luck, and pictures always are welcomed! 😆 
Title: Re: Building log cabin with green logs
Post by: Bruno of NH on December 25, 2018, 07:44:27 AM
I have built many log homes out of green white pine logs.
Do as Andries has said and you will be fine.
Use a good guality log sealant and chinking.
Title: Re: Building log cabin with green logs
Post by: Banjo picker on December 25, 2018, 01:10:16 PM

- Checking is controlled by ripping a 1 1/2" kerf down the entire kength, on the bottom side of your D shaped log. The checking will localize in that kerf, leaving the log looking Purdy.
Excuse me for asking maybe a silly question, but is that kerf deep, or wide?  Banjo
Title: Re: Building log cabin with green logs
Post by: barbender on December 25, 2018, 01:52:44 PM
Deep. Just a single vertical kerf with a chainsaw. On flattened D logs, you could just as well use a circle saw.
Title: Re: Building log cabin with green logs
Post by: Don P on December 25, 2018, 06:01:29 PM
What you're doing there, a check usually forms along the shortest path from heart to bark, you are scoring a weak line to help it form on the bottom hidden face.

One other thing I've done is to take a power planer and make a couple of passes down the center of the bottom. The flat sawn faces dry convex. By making that relief swath down through the middle of the bottom it helps the timbers bear on the outer edges rather than bearing on the bellied middles.


(http://forestryforum.com/gallery/albums/userpics/10017/flatonflat.gif)
 
Title: Re: Building log cabin with green logs
Post by: Escavader on December 25, 2018, 06:18:51 PM
I have seen the walls shrink so much the trusses are held up by the interior partitions.its called truss lift.im not against a green cabin,ive milled alot of them at my previous company.
Title: Re: Building log cabin with green logs
Post by: Don P on December 25, 2018, 09:33:00 PM
The usual way of building for settlement is to think through anything that might hang up when the logs shrink and settle. Interior walls should be built lower than the log walls and then another top plate is attached above them to the ceiling, there is a gap between the wall top plate and the ceiling plate at least as large as the settlement allowance. Then vertical lags, timberlocks, long nails, some form of smooth dowel, is run through a loose hole in the wall plate up to the ceiling plate to hold alignment of the wall. As the log walls settle the gap closes. The upper plate is wide enough to carry a trim piece that slides over the wall finish material, so if a 2x4 wall is covered by sheetrock the ceiling plate is a 4-1/2" wide. 1/4" per foot is a typical settlement allowance for green white pine.

Window and door openings need that allowance as well

A 2 story building gets more interesting, any second floor support girders need to be supported on adjustable screw jacks, plumbing drains need slip joints, stairs, well stairs don't work, they can either slide on the floor and go out of level or slide at the upper deck and lose height at the top riser, better to build the finish set when its done settling.

The triangle up in the gable ends is much easier if framed and sided rather than trying to do in green logs.

There are more details like where the frame walls intersect the log walls, window and door bucks, etc. most has been discussed in other threads or ask if you need more. The main thing is think through every instance where the settling logs confront something that doesn't settle. Caulk is an adhesive, consider that in vertical trim.
Title: Re: Building log cabin with green logs
Post by: firefighter ontheside on December 26, 2018, 07:13:28 AM
My home was built with green red pine.  My logs are natural with just the bark peeled and thejoints were scribedo the next log.  The log walls were originally 10 high and shrunk about 5 over 10 years.  I have allthread running from top to bottom.  In the basement there is a big spring and nut to tighten every so often.  That keeps the log tight as they shrink.  I had to lower interior posts every so often.  As said, you have to plan door and window openings to be able to to close up.  
Title: Re: Building log cabin with green logs
Post by: ppine on December 26, 2018, 10:39:08 AM
Building with green logs is as old as the hills. 
There will be a lot of settling.  Account for it. 
Title: Re: Building log cabin with green logs
Post by: Nsp0005 on December 26, 2018, 09:39:10 PM
Thanks everyone for the replies! If I use screws and put lord down the middle how could expect my logs to settle? Will the entire wall shrink as one unit or will after time they space out Im using long log screws every two feet. Also Id like to add the cabin will be about 1000 square feet. 
Title: Re: Building log cabin with green logs
Post by: firefighter ontheside on December 26, 2018, 09:56:19 PM
I would drill about an inch hole with a paddle bit first and recess your screw in there.  That way when the log shrinks the screw will not lift up on the log above.  I would count on at least a half inch of shrinkage per foot of log height.
Title: Re: Building log cabin with green logs
Post by: Nsp0005 on December 27, 2018, 12:16:06 AM
That sounds like a good idea! So if everyone could pitch in and tell me if Im understanding correctly. Im going to mill a D log I will make 1-1/2 cut down the middle I then will lay my strip and caulk on both sides drill a minimum of 1/2 inch and  recess a screw to leave room for log shrinkage. 
Title: Re: Building log cabin with green logs
Post by: Nsp0005 on December 27, 2018, 12:17:03 AM
I will provide a set of my plans on the morning to see what everyone thinks. Thank you all! 
Title: Re: Building log cabin with green logs
Post by: Greyman on December 27, 2018, 02:51:45 AM
I'm planning on something similar (8" D logs).  We built our family cabin back in 1972 with Douglas Fir logs that were literally trees the day before.  We had to stop and go help the old timer with his big circle sawmill at times and I wouldn't be surprised if some ended up in the building the same day they were felled.  We used 10" spikes with a drilled hole in the top log (6" D logs), about every 3 feet.  Just pay attention as others have noted with things like posts, doors, windows, chimneys, etc.  We have a concrete fireplace/stove pad in the middle with steel posts so it sags down some to the walls but it's not noticeable unless you look for it.  It is on piers though, so we've been able to tweak the leveling to compensate to come degree (i.e. jack the perimeter piers up) over the years.  Everyone keeps trying to talk me into a solid concrete perimeter foundation but I like having the piers for that reason.
We didn't cut the relief or anything like that - just flat with a bit of pink insulation in between that probably doesn't do anything.   The pic below is the best one I have that shows the interior - almost all logs have a crack in the center but I don't think that is bad myself.  Hell, I just watched one of those "log home buying" shows the other day and a $380k log home had cracks like that and the realtor said it added "authentic character"...   :D    


(http://forestryforum.com/gallery/albums/userpics/46158/2017-07-02_19_06_01.jpg?easyrotate_cache=1545896319)
 
Title: Re: Building log cabin with green logs
Post by: snowstorm on December 27, 2018, 06:35:06 AM
here is my option. i built a cedar log home from a kit almost 40 yrs ago. 15 yrs ago we added on. that time i bought the cedar d shape with tongue and  groove. you need that. then 10 yrs ago i bought a repo house to flip. that was pine log. never again. after replacing some rotten logs, several. i put 2" of blue board on the inside then t&g pine. that was the cheapest way to tighten it up. if its just a camp it may be fine
Title: Re: Building log cabin with green logs
Post by: firefighter ontheside on December 27, 2018, 09:32:31 AM
Some of my logs are over 40 feet long and maybe 20 diameter at the big end.  There is almost no visible checking anywhere in the house.  That is because of the saw kerf that is run down the middle of the joint.  I would look for a foam gasket that has adhesive on one side.  Place that close to the inner edge and close to the outer edge.  When the house is done, use a caulk like Big Stretch and run a bead along the outer seams and you should not need it inside.

(http://forestryforum.com/gallery/albums/userpics/36921/DC58A3B6-0201-4482-8D43-092D0198EE8F.jpeg?easyrotate_cache=1540295459)
 
Title: Re: Building log cabin with green logs
Post by: Nsp0005 on December 27, 2018, 10:12:43 AM
Thanks everyone! Would anyone know about the shrinkage in that? Like would my logs individually separate some or would the entire wall just shrink together? I really appreciate all the positive feedback! How would I go about putting my roof on if the walls shrink and windows etc.? Again thank you all!
Title: Re: Building log cabin with green logs
Post by: Nsp0005 on December 27, 2018, 10:13:29 AM
I’m thinking about 1 foot logs for anyone who was wondering as well. 
Title: Re: Building log cabin with green logs
Post by: rjwoelk on December 27, 2018, 02:46:58 PM
I did dovetail joints also screwed the logs down. was not a good idea as the logs shrink in width they could not come together in the dovetail because of the screws and has caused some gaping, which will be closed up with chinking next summer.
(http://forestryforum.com/gallery/albums/userpics/36761/20171105_095303.jpg?easyrotate_cache=1542124872)
 
Title: Re: Building log cabin with green logs
Post by: barbender on December 27, 2018, 03:17:27 PM
I don't like the idea of screws as they can cause settling problems. If you provide relief for them, unless you have springs under them they're not providing any "hold down". On hand scribed log homes, wooden dowels provide the lateral resistance. So will the window and door backs you install. If you want something that will resist uplift, threaded rod that goes all the way from the top plate to the bottom plate is the way to go.
Title: Re: Building log cabin with green logs
Post by: Banjo picker on December 27, 2018, 03:31:36 PM
And if you are like me and too cheap to spring for the whole threaded rod, you could do this...top and bottom.
(http://forestryforum.com/gallery/albums/userpics/18028/20150927_150743.jpg?easyrotate_cache=1443385838)
bottom is hilted in with epoxy.  Banjo
Title: Re: Building log cabin with green logs
Post by: Don P on December 27, 2018, 05:10:35 PM
Thanks everyone! Would anyone know about the shrinkage in that? Like would my logs individually separate some or would the entire wall just shrink together? I really appreciate all the positive feedback! How would I go about putting my roof on if the walls shrink and windows etc.? Again thank you all!

Some things to think about. It's going to sound like I'm being fussy but bear with me for a minute and think about what is going on. Shrinkage and settlement are not the same thing. Shrinkage is the wood shrinking as it loses moisture. Settlement is the logs moving downward, in response to shrinkage. But settlement can be caused by more things going on. In a scribe fitted home like firefighter's there are a few more things causing settlement, compression of the thin edges of the scribed lateral joints. Those edges are bearing on tangential grain which has about twice the shrinkage of radial. The coped laterals spreading as the check forms in them, also called slumping. For anyone interested you can find all of this described in more detail in the log home standard.

The 1/4" per foot I mentioned is from the prescriptive radial settlement table in that standard, for a milled white wood log in a warm humid climate drying from fiber saturation point, green to dry.  Can you go more, in most cases it doesn't hurt anything. During the development of that code a number of us wrote in to disagree with the logic behind that table, in the real world the settlement is actually less. Why. First, the settlement allowance is based on shrinkage data from the USFPL. Those shrinkage numbers were based on very thin radial and tangential samples, free to move in response to moisture changes. A full sized timber doesn't shrink as much as a piece of veneer because it is somewhat bound internally by differing stresses and rays. Second, when a check forms the wood has indeed shrunk but the dimension of the timber has not changed as much as the amount of shrinkage. Part of the shrinkage is in that check.

Will your wall shrink uniformly, all together and remain perfectly tight or will there be some separation. There will probably be some separation. For one the shrinkage numbers are averages, each log is an individual and will shrink somewhat differently. Not all will be straight grained, some will twist to a greater or lesser degree. Some will have knots, ever notice in a dried board that the knots are proud, longitudinal grain perp to the axis of the board.

To settle around a fastener, any fastener, the rows of fasteners need to be plumb. If they wander around at divergent angles nothing is settling. If a log twists as it dries it is certainly going to put friction on the fasteners before allowing any settlement. Can a 2500 lb spring overcome the twist and bow of a large drying timber? Can you stack an entire wall of such timber and then successfully tighten it all? Will all members be in plane? One group of chink builders intentionally builds log homes that do not settle. They drive rebar at opposing angles from row to row to lock the height. The logs shrink individually but are hung in place on the opposing pieces of rebar.

The roof springs from the top course of the log walls, assuming it is only bearing on the logs, as they settle the roof is simply along for the ride. As long as the logs settle somewhat uniformly and that it isn't tied to something that doesn't settle, like a chimney, the roof remains in plane.

Title: Re: Building log cabin with green logs
Post by: Nsp0005 on December 27, 2018, 07:19:07 PM
Yeah thats why Im doing butt and pass method to avoid that. 
Title: Re: Building log cabin with green logs
Post by: pappy19 on January 02, 2019, 07:34:58 PM
Why not just use standing dead? I used standing dead Idaho white pine and have lived in our log home for 18 years. Swedish cope round logs, 3 stories and no movement whatsoever.
Title: Re: Building log cabin with green logs
Post by: arky217 on April 21, 2019, 07:23:21 PM
Some of my logs are over 40 feet long and maybe 20 diameter at the big end.  There is almost no visible checking anywhere in the house.  That is because of the saw kerf that is run down the middle of the joint.  I would look for a foam gasket that has adhesive on one side.  Place that close to the inner edge and close to the outer edge.  When the house is done, use a caulk like Big Stretch and run a bead along the outer seams and you should not need it inside.

(http://forestryforum.com/gallery/albums/userpics/36921/DC58A3B6-0201-4482-8D43-092D0198EE8F.jpeg?easyrotate_cache=1540295459)

I'm building a small (12'x12') log cabin out of green southern pine using sort of the same strategy.
Using approx. 10" logs, I'll be milling 3/4" off the tops and bottoms.
This leaves the log 8.5" thick with a 5.5" wide flat on top and bottom.

Then I'll cut a kerf 3.5" deep on the bottom to help prevent checking. I'll use a modified butt & pass
method in that I'll drill a 1/2" hole thru the top log and 5" into the bottom log. Then I'll enlarge the
hole in the top log to 5/8".

Then I'll drive a 13" length of 1/2" rebar so that's it's recessed 1/2" into
the top log. This way the rebar will be tight in the bottom log and will allow the top log to settle and
stay snug to the bottom log.

But I have a question about using a 1/8" thick x 5.5" wide strip of sill foam between the logs.
I plan to lay down the strips as I assemble the logs since the logs should stay snug to each other
which would make it hard to wedge in the foam strip after assembly.

But the question is, will the foam strip hinder the purpose of the kerf cut by sealing it off.
Perhaps I should forget about the foam strip and just caulk the outside joints after assembly.

I would like to use the foam strip but not at the cost of checking.
What do you think?
Title: Re: Building log cabin with green logs
Post by: Don P on April 21, 2019, 08:12:39 PM
Foam really needs somewhere to live to be able to recover. It doesn't recover if smashed flat. You also don't really want it creating dimension.
Centered on the bottom flat, straddling your kerf, run a power planer a couple of passes up the length of the underside of the log, creating a plowed out wide, shallow groove. Stick the foam in that, then it doesn't interfere with log height and the foam is not crushed. Flat faces  become convex as the timbers dry, this will keep the logs bearing on the outer edges of the plowed groove. Fastening the logs down with screws in counterbored pilot holes lets you get them tighter to begin with, something I've never been able to do with any dowel type connector, pins, spikes, rebar. At least take that out of the gapping equation. Allthread drilled in as you go can allow you to keep tightening the stack later.The foam will not prevent the drying stress from concentrating on that weakest radial part of the log, it is a stress concentration point rather than a drying point.
Title: Re: Building log cabin with green logs
Post by: arky217 on May 08, 2019, 11:19:14 PM
Foam really needs somewhere to live to be able to recover. It doesn't recover if smashed flat. You also don't really want it creating dimension.
Centered on the bottom flat, straddling your kerf, run a power planer a couple of passes up the length of the underside of the log, creating a plowed out wide, shallow groove. Stick the foam in that, then it doesn't interfere with log height and the foam is not crushed. Flat faces  become convex as the timbers dry, this will keep the logs bearing on the outer edges of the plowed groove. Fastening the logs down with screws in counterbored pilot holes lets you get them tighter to begin with, something I've never been able to do with any dowel type connector, pins, spikes, rebar. At least take that out of the gapping equation. Allthread drilled in as you go can allow you to keep tightening the stack later.The foam will not prevent the drying stress from concentrating on that weakest radial part of the log, it is a stress concentration point rather than a drying point.
Very good answer; thank you.
I like the idea of using a power planer as you suggested;
I didn't realize that the flat surfaces would become convex as they dried.

Another thought occurred to me about my intended plan on enlarging the hole in the upper log
so that it will settle down on the rebar as the logs shrink.

I intended to redrill the 1/2" hole in the upper log to 5/8" to accomplish this,
but what with the possibility of the logs twisting or otherwise deforming as it shrinks,
I now wonder if I should increase the size of the hole in the upper log to 3/4"
to make sure the upper log will stay down on the lower log and not bind up on the rebar.

What do you think ?
Title: Re: Building log cabin with green logs
Post by: Don P on May 09, 2019, 07:36:26 AM
The convex flat surface is a result of the shrinkage difference between radial and tangential grain. Tangential shrinkage is about double radial. The center of a boxed heart timber is radial and the outer edges are tangential grain.

If the rebar is free in the upper log and there is no "head" on the fastener... what is it doing? It isn't helping to draw things down during assembly or holding down a twist, and it isn't helping with uplift. Is this just a loose lateral restraint? If you want to hold the upper log down on the lower log I think you'll have more luck with allthread from bottom to top in loose holes with a big plate and nut top and bottom. I doubt you can crank the entire stack down fully tight but certainly much more than just the weight of the stack.
Title: Re: Building log cabin with green logs
Post by: Stephen1 on May 09, 2019, 08:16:26 AM
One other item to think about is the length of your wall. From what I had studied when I built my place was no log wall should be longer than 20' as they have tend to spring out, or in. An interior wall or a corner is recommended. It might also be different with rebar or log screws every 2'
DonP might weigh in on that.
 I was told at the time that 3/4' shrinkage for every foot of wall height. 
DonP I understand after reading your post what you are talkiing about with the flat logs. Mine is A scribe home so a height shrinkage rate is increased.