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OutsideFun1
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# Posted: 27 Mar 2014 22:23 - Edited by: OutsideFun1
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I'm looking to build a simple log cabin in a year (this year I'll be felling the trees, stripping the bark, and letting them season for a year before I begin).
I haven't decided on the dimensions yet, but I'm thinking somewhere between 15'x20' and 20'x25'.
I live in mid-southern Ontario, and the winters here get down to around -15c on average, and into the -20s when it gets really cold.
I want to build this cabin as cost effectively as possible, without sacrificing quality (but who doesn't want to do that?)
So here's what I've been wondering. I've been trying to figure out the easiest, cheapest way that I can put this log cabin on a PROPER foundation.
Cement slabs are neat, but they are very expensive.
I like the idea of a pier foundation, but I'm not sure what spacing would be needed. Also, I imagine that a pier foundation won't necessarily be the cheapest to do either (although much cheaper than a slab of course).
I'm also wondering about placing several big boulders beneath the cabin. This would obviously be the cheapest solution. However, I'm not sure what that would entail. I've seen that pretty much all pioneer log cabins were placed on boulders, and most of them seemed to last for a while (a century or two). But I still wonder what the risk would be of shifting and heaving?
Anyway, those are my thoughts. What do you guys think is my best option? And how would you go about it?
Thanks!
OutsideFun
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bldginsp
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# Posted: 27 Mar 2014 22:40
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Is there enough rock around to build a rock wall footing around the perimeter?
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OutsideFun1
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# Posted: 27 Mar 2014 22:43
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There are several boulders on the property and a TON of field stone.
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MtnDon
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# Posted: 27 Mar 2014 23:24 - Edited by: MtnDon
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Keep in mind that most old log cabins were built from materials at hand and built as quickly as possible as shelter was needed. Foundations on rocks of assorted sizes were common as the old builders used what they had laying about. We see some old log buildings surviving in reasonable condition. What we don't see are all the failures, like one near our place in the mountains in NM.
IMO, a pier foundation is about the worst to use. If you have lots of rock a rubblestone foundation with a solid footing to proper depth would be more suitable. Proper footing depth is a key component for a long lived foundation and building. Large boulders sitting on the earth above frost depth can still be heaved by freezing. A lot of effort goes into the harvesting of the trees and the construction of the building. More effort than a stick built structure. Myself, I would not want to chance building on an inferior foundation.
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leonk
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# Posted: 28 Mar 2014 16:21
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Depends how much you're willing to spend.
I'd build on boulders. You can adjust it with a jack if it moves - much cheaper, than 'proper' foundation. I'd cut floor joists into the sill log, this way, the whole thing moves together. Just make sure you build in a good spot and there's no spring run off around the stones. Divert the water if you have to.
I Siberia, even today, hunters build small log cabins by placing logs on the ground. They use larch, if it's available for the sills. But if not - whatever wood is there. The cabins stand for many many years.
Where r u in ON?
So you're cutting your own logs? I just read, Latvians prefer to cut the trees in the first quarter of the moon  Chambers doesn't think this is nonsense either.
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adakseabee
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# Posted: 28 Mar 2014 16:53
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In view of your comment that you have a "TON of field stone" I second MtnDon's recommendation for a rubblestone foundation. As he said, it is necessary to have a proper footing depth, i.e., below the frost line, AS WELL AS drainage at the bottom of the trench running to daylight to ensure water does not accumulate within the rubblestone. Use filter cloth to cover the trench sides and bottom while filling the trench with the stone to keep soil from clogging the drainage system.
As for what is proper frost line in your situation, I would be very conservative. Consult local college/university, builders and building inspectors to determine how deep the ground freezes in the worst of cold winters. In your location considering how cold it gets there, I would certainly not go less than four feet.
On top of the rubblestone which completely fills the trench that would otherwise be a solid reinforced concrete or concrete block walls on top of a reinforced concrete footing, you could install a reinforced concrete grade beam. The width of the rubblestone foundation and the width and depth (height) of the grade beam should be determined by an analysis of the anticipated dead and live loads the foundation system of rubblestone and grade beam would support.
Use of this system solves several problems that might be a concern: less concrete and steel is used in this type of foundation than a normal full wall concrete/concrete block foundation which reduces cost of materials and labor and the amount of Portland cement that needs to be used (a "green" concern), frost heave is mitigated through drainage, the sill logs can be raised well above the ground level by the height of the grade beam which helps to prevent rot, and the trenches offer a good place to dump all of that field stone that you may want to remove.
If you have any doubts about this type of foundation, I encourage you to Google "Grade Beam on Rubble Trench Foundation". There are a lot of photo examples and articles about this. No less an architect and builder named Frank Lloyd Wright used rubblestone foundations in his buildings. BTW, the term rubblestone is synonymous with rubble trench.
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bldginsp
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# Posted: 28 Mar 2014 17:21
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The only place you don't want to use rubble stone is in a serious seismic zone, since they offer no lateral strength.
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Don_P
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# Posted: 28 Mar 2014 23:06 - Edited by: Don_P
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we're talking about two different things here with regards to rubble trench footings and rubblestone foundation walls.
This is a pic of rubblestone foundation walls, and chimney. In the US they are a minimum of 16" thick for uncoursed solid rubblestone walls. We did incorporate rebar in the tall wall on the right and in each porch post support column to help with lateral strength. This was fieldstone gathered by generations of farmers, we were fortunate enough to be able to just collect their piles around the field edges. The footings under the stone walls are conventional frost depth full perimeter spread footings. And yes, rubblestone walls are forbidden in highly active siesmic zones. Of course, undesigned piers or a boulder on the ground have even less lateral resistance and wouldn't pass muster anywhere so in all things, perspective.
The concrete walls you see actually supporting the house visible by the garage door are precast foundation walls placed on gravel footings, a form of rubble trench. Interestingly enough we had a small tremor while in construction. My wife was inside up on 3 bucks of scaffold, she should have been swaying. We didn't even know a tremor had happened till a neighbor came over who had been awakened from a nap by the vibration. The only thing we could figure was the gravel footings isolated us a bit from the ground motion.
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leonk
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# Posted: 29 Mar 2014 08:13
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OP asked about small cabin in ON. It's not a seismic zone and my assumption was he's trying to build on a budget. This is why I said I'd build on boulders. Of course proper foundation is better, but he's not building a 'house'. Again, A B Mackie build his house on boulders in ON.
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bldginsp
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# Posted: 29 Mar 2014 10:02
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Very nice building DonP, but of course we were talking about stone with no mortar, rebar, concrete.
A poster named Smawgunner here on the forum bought a property in Ohio (?) with a 150 year old two storey log house on a rubble footing, which evidently had not had serious repair in years. He only had to do minor repair to the rock, and I don't think his sill logs were rotted. That footing is at least one foot above dirt all the way around.
Wish I could do that here in Earthquake Land (Calif).
Boulders would be fine so long as they are buried to frost depth. But I don't want to be the person moving those things.
There is a science to mortarless rock wall construction, be it a rubble footing or a sheep pen. Plenty of info on the web, but basically the outside pieces of stone need to be always placed so that they lean inward, toward the center. Sounds obvious and easy, probably not so easy in practice.
Anyone here actually built a mortarless rubble footing, or wall?
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Truecabin
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# Posted: 29 Mar 2014 12:23 - Edited by: Truecabin
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a real foundation may cause a permit
would be great if the ground is firm or rocky
if the concrete is not visible maybe you can say its a temporary structure
dig below the frost line and fill the hole with concrete & rocks and set the boulders on the concrete then pot them in and hide the concrete
get it up off the ground let the air blow under it
dont worry about earthquakes in a log cabin on the ground
or you can level it as said above with a couple 20ton jacks it gets simpler to level it again if you have only 4 corners
log cabins arent for everybody
else home depot would sell them
its a special project for a special place
and good exercise too will either keep you young or make you old
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fpw
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# Posted: 29 Mar 2014 12:58
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Dig hole below the frost line, fill it with concreate and rebair and pin a stump to the top. Call her good.
My cabin is 20' x 22' inside dimesninsions. I used three main log joists for support. On the two outsided edges I used 5 piers. On the center I used three piers.
shear3.jpg
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bldginsp
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# Posted: 29 Mar 2014 15:54
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Truecabin-
Any foundation will trigger a permit if a permit is required and it comes to that. There are no 'temporary buildings', and a rubble foundation will still be required (if required) to have a permit. I just don't want people to think a non-concrete foundation avoids the permit process, or that you can avoid it with a 'temporary' building. It's up to each individual how they want to deal with the permit issue, but whatever you do it's best to come into it with a clear picture.
I think you do need to think about seismic with log cabins, if you are in an active seismic zone. All that weight shifting off the footings in a serious lateral event is just as dangerous, if not more so, than a stick frame building.
But, I suppose, opinions differ
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Don_P
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# Posted: 29 Mar 2014 17:32 - Edited by: Don_P
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They do, that sounds like shooting from the hip, I'm being good natured, no offense intended
Log is lighter than say brick veneer stick frame, we can go through material weights, and it might be a fun exercise, but I suspect dead load isn't too dissimilar. Log walls themselves have generally done well in wind and flood events, I believe Thomas Hahney did some seismic engineering paperwork for log buildings but can't recall with certainty. Go back up to the original post though, we were being asked to describe a proper foundation. I'm assuming we are being asked to suggest ones that are code compliant and could make it through permitting? If so boulders, dry laid, piers or stumps are out. Generally, look at your local codes for what is prescriptive for the most affordable options. A permanent wood foundation on a gravel trench is another option.
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fpw
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# Posted: 29 Mar 2014 18:00
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Log Standards
http://www.logassociation.org/resources/ilbastandards.pdf
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bldginsp
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# Posted: 29 Mar 2014 18:44 - Edited by: bldginsp
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DonP-
You may be quite right that log walls are the same weight as some stick walls, or lighter. And I'm sure that a well engineered log structure will do well seismically. But, if that log structure is not connected to earth by some means or other, and not connected to the foundation, it will be highly likely to come off the foundation in a lateral (side motion) event. Also, a rubble wall will just fall apart in such an event. Seismic engineering begins with anchoring to earth.
The ILBA standards don't address this issue, since it is a local jurisdictional issue that varies with seismic zone and relative wisdom of the people in the jurisdiction.
Yes he did ask for a 'proper' foundation. If by that he means code compliant, he'll have to talk to the local department. If he meant one that will work well, that's another thing. A code compliant foundation will work well (hopefully) but may be a lot more than one can or wants to do.
These log on gravel in trench footings are interesting- certainly easy. I wonder if they are accepted as compliant anywhere.
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MtnDon
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# Posted: 29 Mar 2014 19:02
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Quoting: OutsideFun1 PROPER foundation.
Note that proper was even in CAPS in the OP. To me "proper" means one that will meet building code without requiring an engineers calculations. The building codes specify methods that can be used without engineering input; just copy an approved method. Codes make allowances for outside the box in all aspects of design and construction; there's a catch all phrase that directs one to engineered or approved methods. ( or words to that effect). Makes it simpler for a DIY and helps keep costs down while making a stronger product than most seat of the pants, "that looks about right"....
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bldginsp
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# Posted: 29 Mar 2014 19:12
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Outside of seismic zones, foundation rules are far more lax. All you need is adequate down bearing.
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Don_P
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# Posted: 29 Mar 2014 20:43 - Edited by: Don_P
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Outside of seismic zones, foundation rules are far more lax. All you need is adequate down bearing.
Why do I sense a tiger has me by the tail
All foundations must be capable of withstanding lateral forces... actually up, down and sideways. When outside of a high seismic zone, wind controls the lateral force design. All lateral force collected by the building must be transmitted to the foundation and the ground. In the US that is the reason for the curtain wall in a pier and curtain wall foundation, the curtain wall resists the shear, and that is the main reason a pier foundation requires engineering, the soil is providing that lateral force resistance and the layman has proven to be ill equipped to do that design. In a permanent wood foundation (and in a sheathed stick frame wall) the sheathing provides that bracing and is securely fastened to the studs to prevent the sheathing from buckling when its' well nailed perimeter resists the racking forces of either an earthquake or a windstorm. With a poured wall or block foundation the continuous walls resist the lateral forces. Lateral force design is always there in a proper foundation just as in a properly braced wall. when we build prescriptively we don't have to perform those design calculations, we are using methods that have proven themselves as long as we stay within those prescriptive methods. When we step outside of those prescriptions, it is proper to call in an engineer to check the proposed design.
This project is in ON so their rules apply, in most of the US, for a rubble stone masonry wall, look at my photo above or at code section R404.1.8.
http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_4_sec004.htm?bu2=undefi ned
This is not a dry laid foundation but it can be relatively cheap to build if one has the stone and the time. The anchorage and footing requirements are the same as for any proper foundation. It is limited to seismic zones C and below. Slip forming is a bit faster and is another way to do a rubble stone foundation.
The ILBA standard should not to be confused with the code referenced log building standard.
A log on a gravel trench probably doesn't meet the requirement of keeping wood at least 8" above grade (preferrably more for a log)
For proper, the devil is certainly in the details, but it is not as onerous as it might at first seem and there are many ways to get there while still being "proper" in the code compliant sense.
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bldginsp
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# Posted: 29 Mar 2014 21:10
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I've got you by the tail, now I'm going to swing you around!
No just kidding. You're quite right about wind shear. We deal with that a lot less here in sunny CA than in the rest of the country.
Tell me Don- how do you get anchorage into a rubble foundation with no concrete? Or does a compliant rubble foundation require mortar to set bolts?
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Don_P
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# Posted: 29 Mar 2014 23:22 - Edited by: Don_P
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LOL
Yes, I think you are in 90 mph wind country. Depending on elevation and topography I'm in one of those "special wind regions".
The full name of that foundation is "rubble stone masonry", by masonry they mean a mortared wall. So the anchor bolts are set in the masonry/ mortar just as in a brick masonry wall. There is no prescriptive dry stacked foundation although I have repaired a few older ones. To go a little deeper rubble stone masonry is considered "plain masonry" as opposed to "reinforced masonry" that is, there is no steel reinforcement in the prescriptive wall. We worked steel into the chimney, tall wall and into the piers supporting the porch columns.
Going more into another set of related details might give more insight into the thinking process of design. More of the detail devils.
For the porch columns the steel was for uplift more than anything, where in the chimney it was for overturning. If the wind gets under the porch ceiling it could potentially lift the columns or tear off the porch roof. I ran a couple of bars with a hook on the end into the footing and up through the columns. Across these at bottom and top porch railing height I drilled 1/2"x2" flat bar stock, slid it down over the rebar and welded it to the rebars. These flat bars projected out the sides of the columns to give mounting points for the railings but also reinforced the column. From the upper horizontal bar a 1/2x4" piece of flat stock was welded that projected vertically thru a slot in the bluestone caps and 6" up into the oak posts. The posts were drilled, thru that hidden knife plate and pinned with 2@ 1/2" steel pins. The holes were then plugged with oak pegs. The tops of the posts were lagged to the horizontal bolsters that were then connected to the porch carry beam with steel angles. The rafters were hurricane tied to the carry beam. This gave us the "continuous load path" that is required as part of the "main wind force resisting system". Google MWFRS for more reading on that lateral than you ever wanted to know.
Once the design devils are beat back the fun part begins. I see that fun in fpw's gin pole pic too, I really enjoyed that. We cleared the site in my pic by dropping the (mostly) oaks into the construction area. Called in a portable bandmill and sawed out the porch timbers. They were stickered and covered to season while we gathered the stone and began to build the house. When the main house was dried in we set up shop in the basement and made the porch posts. As they were roughed out I set them in a dip tank made of plywood and soaked them in a borate solution, dried the parts, final assembly, sanded, oiled and then set them.
That was a long winded aside, hopefully kinda fun, now back to our regularly scheduled problem at hand
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MtnDon
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# Posted: 30 Mar 2014 00:31 - Edited by: MtnDon
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The fun is in hearing about the hidden details of the craftsmanship. No casual pile of rocks is that.
For full disclosure Don_P and I know each other and I have walked admiringly around that house in it's incomplete state, though after that roof was finished. 
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bldginsp
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# Posted: 30 Mar 2014 10:26 - Edited by: bldginsp
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Quoting: OutsideFun1 So here's what I've been wondering. I've been trying to figure out the easiest, cheapest way that I can put this log cabin on a PROPER foundation.
Back to OutsideFun's original question, I suggest the following-
-make a section drawing of a foundation trench, dug to frost depth and 16" wide. (could be 12", but you need elbow room laying rock)
-Show rubble stone with mortar, and one piece of #4 rebar in the bottom, one in the top, with stone mortared around the rebar.
-Show bolts set where needed by building design, but always wired to the top rebar
-show the top of the footing 8" at least above the soil
Take this section drawing to the building dept. and see if they will accept it as part of his larger set of plans.
What do you think OutsideFun? I think this thread went a bit past what you were intending, informative as it is.
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Don_P
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# Posted: 30 Mar 2014 10:56 - Edited by: Don_P
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I'd draw a second foundation as an alternative. I like adakseabee's suggestion of a rubble or gravel trench (see the foundation chapter link I posted for a detail sketch and table). Pour a grade beam to finish grade as he suggested. This all gets you out of the mud quickly and relatively cheaply. Then draw a 16" thick rubble stone masonry perimeter wall on top of the grade beam. This gets you a visually pleasing yet low cost compliant perimeter foundation wall.
One more aside, I've done it this way several times. It is faster to build a temporary plywood back form on the unseen inside of the rubble stone wall. This gives you something to quickly work against on that face. We had a very good stone mason doing the one in the pic above, he used only mortar and fitted the rock very nicely. When I've done it, I initially mix a batch of pea gravel concrete rather than mortar. Spread a couple of shovels of that on the footing and lay a row of stone. Spread the next few shovelfulls, slammed against the back formwall and spread shy of the face and bed the next course. Keep repeating that process and then rake the face of the joints out a couple of inches deep. When that has set come back with a rich mortar and point up the joints with that. The joints are wider, set deeper, and unworked, a more casual look. The wall is stronger than spec, steel can be laid in whenever you want and it is relatively fast, depending on how fussy you want to be.
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Truecabin
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# Posted: 1 Apr 2014 23:32 - Edited by: Truecabin
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Quoting: OutsideFun1 I'm also wondering about placing several big boulders beneath the cabin. This would obviously be the cheapest solution. However, I'm not sure what that would entail. I've seen that pretty much all pioneer log cabins were placed on boulders, and most of them seemed to last for a while (a century or two). But I still wonder what the risk would be of shifting and heaving? Anyway, those are my thoughts. What do you guys think is my best option? And how would you go about it?
if your going to build your own log cabin and its small, try to put it on boulders dont mix home depot and logs thats my opinion you will have a cool place if you build it old style
i dont know where you can find out if your ground is ok for boulder foundtion nobody knows this anymore because they only know code
large flat boulders will be better for everything and earthquakes too
if you want to use boulders then i guess that means there are some nearby
in the springtime look around for boulders submerged in the dirt do they show evidence of frost heaving? i bet there is a specific time in the spring when you can see this
of course if there were any cabin examples in your area to look at then you wouldnt be asking but if you need a permit like the guys above said then you have to use code
like the guys said it can be very hard to know if you can get away without a permit most places are worse than others 
but aside from falling on your toe it takes a big earthquake to bother a small square log cabin they are solid wood
shooting from the hip - yep id say 20x25 is getting up there for doing your own engineering & building your first log structure 15x20 sounds better then 4 boulders seems ok
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neckless
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# Posted: 2 Apr 2014 14:32
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i have built my 16x20 bunk house on railway ties and it has not move in 7 years, but it is in sand gravel mix,,,even drywall half the in side , no cracks yet bury a tie level with ground,add a 3x5 treated plank atop , mix batch of motar grout corners and joints sow mice can get under cabin build two foot pony wall and beam in centre ,, now is time to insulate , i put 2 and a have in blue that i got from a roofer than treated 5/8 plywood... now thats a good foundation,,, and can heat with a candle here in northwestern ont . ca.
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Truecabin
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# Posted: 3 Apr 2014 10:14 - Edited by: Truecabin
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all log cabins settle even if built very carefully
if you cant figure out what to do if the foundation settles a little you are not the type to build your own cabin anyway
but you know where you are on that and who cares if it moves an inch or so
a lot of code is to protect the insurance industry and the contractor to and protect the homeowner against those two but its a twin edge sword
you said you want to build it simple but if you ask bldg dept even the first question your dream is sunk right there
if you press forward with a permit you might as well open an account at home depot like everybody else cuz you aint having a log cabin  be careful out there and pay attention
a 15x20 log cabin wont collapse and it wont fall on your toe if you can avoid code your building can be low cost as you want but the cost is your hard work and i love that kind of work
i like to know some other people will work hard to make a cool cabin because im a cabin nut
but as everybody will tell you its hard to know if you can get away with it put your thinking cap on and look around and dont say too much
better not cut nearby trees you will need some to hide it from satellites the square roof shows up real good no matter what you do the only thing you can do is hide under evergreen trees and dont use metal roof that helps a little
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Don_P
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# Posted: 3 Apr 2014 21:25
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Both those foundations were built to code, and well, using local rock and a fair amount of hard work. They will neither heave nor settle. No one is going to have to revisit the foundations for the life of those structures. that last pic was from a restoration job on an 1840's log home. Sometime between then and 1865 the NW rock pier failed and the load found a new path, the chimney centered in the west wall bore the load although a poorly built shallow perimeter foundation was put under it then. I found the overturned walls as I excavated. As they took load they failed and tipped into the yard. Over the next century the logs spanning the chimney bowed over that support and took a permanent set. Always interesting to see how things work over the long haul. In those old cabins the main floor was independent and inside of the log wall on it's own piers, making it easier to relevel or replace the floor. I put the third floor system in it and the third foundation under it. The sixth generation of that family still owns it and it will go to the seventh who was able to stay in it after the restoration.
If you'd like to have a log home where the logs don't settle, check into piece-en-piece log construction. B.A. Mackie has some examples in "Building with Logs" and "Notches of all Kinds" or James Mitchell's "The Craft of Modular Post and Beam".
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Maxwake
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# Posted: 7 Apr 2014 11:39 - Edited by: Maxwake
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Building small 8x10 building for toilet and shower. Struggling with all info on necessary foundation. Base is treated 2x6s with 3/4 treated floor. Was planning to put those on either 2x8 or 2x10 beams. Could I put those simply on concrete blocks (the pier things)? Do I need the 2x8s? I'd like idea of it being up off ground. That seems much easier than digging and doing concrete. I'm new to all this. Ground is sandy and fairly flat. It's cold climate with lots snow.
Sort of figured I need concrete 4 feet down and then 4x4 posts to attach the beams to but some things on this chat made me wonder if that's needed?
Any advise appreciated
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Truecabin
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# Posted: 7 Apr 2014 12:00 - Edited by: Truecabin
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8x10 is a small building easy to support and if built up off the ground its easy to fix any problem
you can lift a corner of the building with a 2x4 lever and add a block to level it again
2x6 joist on 3/4 is strong your done there dont worry
time and money on a 100 years foundation is wasted your talking about an 8x10 outbuilding
for 8x10 hope owen chritsenson replies he knows the short answer and explains it well
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