Let me tell you something about cordwood construction. It is beautiful. It is charming. It is rustic. There is a ton of information online and in books on this subject. I will also tell you that to find specifics that actually work is a whole other story. Your best best, hands down, is to find someone who you can actually talk to. Someone who has experience. And by experience, I mean years of experience in actually building multiple structures, possibly in multiple conditions, if at all possible. Find a workshop, and go. For me, I have not been able to find a workshop within a reasonable distance, so, unfortunately, the information that I am presenting here is coming from a number of sources, none of them personal. But, in an effort to provide you with the best information that I can, I am going to tell you what I've found - all the contradicting info out there. From there, it's up to you. But again, on this one, I STRONGLY urge you to find someone with lots and lots of experience that you know you can actually trust to learn the best possible information from. That being said, let's start down this somewhat crazy path of cordwood construction.
So what exactly is cordwood. Well, basically, cordwood is really any wood that would otherwise be wasted or not able to be used for traditional construction. A "cord" is a unit of measurement. When the wood is well stacked and relatively compact, a cord is a volume of 128 cubic feet, or 3.62 cubic meters. A cordwood wall provides both insulation and thermal mass. Insulation is from the wood, and whatever other insulation you may decide to use. Thermal mass comes from the mortar. The basics of building with cordwood is actually quite simple. Cut all your pieces to roughly the same length, stack and mortar the pieces like brick or stone to then build your wall. Simple, right? Well, it should be. While pretty much everyone will say that is simple enough that a child can do it, that's about all that is agreed on. At the end of this post, I will include a few site links with information, some chat threads, and whatnot for you to look through and make your own judgments.
Let's start with a foundation for your walls. Some sources say that you can start building directly on your foundation, or even directly on the ground. Other sources say that the cordwood should start no less than a foot above the ground, preferably, more like two or more feet, so as to keep rain, snow, or whatever other kind of moisture could possibly get into your wood, out. Having it raised, the advocates say, also greatly limits the amount in insects you'll end up dealing with. I would tend to agree with the later sources. Again, I have no personal experience, but, quite frankly, it just seems to make more sense. Build the wall, much as you would cob or adobe, with a stone, or other solid material, foundation. If nothing else, I, personally, think that makes the exterior that much more interesting and attractive.
For the actual cordwood section of the wall, some say that you can simply use the wood and mortar, especially if you don't need much in the way of insulation. Others say that when you lay the wood, the mortar goes on either end of the wood, and then the center portion, rather than more mortar, use an insulating material. With the insulation, there is disagreement on what is best. Some say simple sawdust is enough. Some say a combination of sawdust and lime. Some say modern foam insulation. As for the mortar, there is debate on whether or not to use modern concrete mortar, or a natural mortar, such as cob. Supporters of cob insist that using concrete will keep the walls from breathing properly, which, as we should all know by now, is one of the trademark characteristics of most natural walls. Nor would the concrete allow for natural compaction and expansion of the wood over time. On the other hand, if cob is used, then it takes extra work to take care of the wall, including a larger overhang in order to keep moisture from coming in from the top.
Now, let's talk about the wood itself. What kind do you choose, and what do you have to do to it? Is there any agreement here? Nope. No such luck. Now there does seem to be one common theme, in that most sources do say that it's better to use softwoods rather than hardwoods. The reasoning behind this is that softwoods hold up better over time, and are generally easier to season, or dry. Another complaint I've seen is that hardwoods generally tend to have higher amounts of oil in them creating stronger scents that some people can find offensive. I would say that's a personal opinion, but the other sounds logical. The seasoning or drying of the wood is yet another topic for disagreement. All say to remove the bark, which is primarily what attracts insects and disease, and also holds in moisture. Beyond that, well.... Some say to remove the bark while the tree is dormant. Some say to remove it in the spring while the sap is flowing, making removal easier. How long does it take to dry? Some say that only 3 - 4 months is ample time to season the wood. Others say that a few months is no where near enough time, but rather you need at least 2 -3 years for the wood to completely dry out. To use the wood after a shorter amount of time, according to the proponents of the longer time frame, is to vastly increase the chances that your wood will not be dried out enough to keep it from rotting. Rot happens because of moisture. Disease, insects, and all of the other things that can possibly happen to wood to cause it to degrade happen due to moisture. So, according to these sources, when the wood is truly seasoned over a longer period of time, what that means is that there will be much less expansion and contraction of the wood (which will happen over time, to one extent or another, as atmospheric fluctuations happen), leading to less upkeep, and practically eliminates entirely any need for chemicals of any kind to seal or treat the wood. They say that once the wall is built, there really is almost zero upkeep needed, if it is built properly to begin with.
Cordwood buildings are beautiful. And the actual building, regardless of the method followed, does seem to be one of the simpler building methods. It also lends itself quite easily to variations. Use different shapes and circumferences of wood to create patterns and designs within the wood. Integrate colored bottles into the walls for interest, added color, and extra light. Use it for the entire building, or for only one accent wall. Some areas do require some sort of post and beam frame in the codes, but even that can have it's charm. The possibilities here are massive. If you can cut through all the conflicting information and find some real information from a truly reliable source, this is a great option that can be adapted for just about any climate.
http://cordwoodmasonry.com/
http://cordwoodconstruction.org/
http://www.greenhomebuilding.com/cordwood.htm
https://www.niftyhomestead.com/blog/cordwood-construction/
https://cordwoodconstruction.wordpress.com/
http://www.greenhomebuilding.com/QandA/cordwood/misc.htm
https://permies.com/t/8654/cordwood-houses
http://www.motherearthnews.com/green-homes/ask-our-experts-shrinkage-of-wood-in-cordwood-construction-zm0z11zblon
http://www.masterjules.net/cordhous.htm
http://www.homesteadingtoday.com/general-homesteading-forums/homesteading-questions/118815-cordwood-masonry.html
http://www.minimalisti.com/home-garden-design/10/cordwood-house-cordwood-construction.html
http://cordwoodconstruction.org/img/Why_Cordwood.pdf
http://www.dirtcheapbuilder.com/Home_Building/Cordwood_Masonry.htm
http://www.greenhomebuilding.com/QandA/cordwood/seal.htm
http://www.lifeunplugged.net/greenbuilding/build-a-cordwood-home.aspx
http://www.appropedia.org/Cordwoodguy%27s_cordwood_guide
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