Hi Ian,
Good to hear back from you...and all here are more than happy to leaned a word of advice when and if able...
My email is at the bottom of each post...feel free to use that as others do all the time to get more specific, and then I try to always bring the results back here for "public sharing," feedback and examples of projects outcome...
I am working really hard at getting this current little project at Sharon Elementary School here in Vermont done, as the means, methods and materials would probably really help a lot of folks think through what a project "really needs" compared to what they "think they need to do." The post I am writing for it will outline all the steps and give a "framework" of one example of "basic natural building. From that all manner of "augmentation" like light
cob, straw bale, cordwood infill or more mainstream combinations of those and wall trusses with mineral wool board/batt insulation. It has a broad range of applications and biome types it could be "fitted into." I bring this up because "I think" it may help you address and think more about your own foundation challenges...
I don't think you will be displeased following the "vernacular format" of the current log cabin you live in. As suggested...it is a well proven modality.
Now for
#1
but nothing consistently big and straight enough to build the entire house out of the same species (something I have been told to stick to, and seems logical because of shrinking rates).
Nope...not true at all...and more "modern day" myth than truth...I have worked in vintage houses with more than 5 different species in the framework and floor. I have facilitated one with over 23 different species of hard and soft wood. So mixing and matching is more than plausible...IF...you understand the species of wood you have selected and how it "typically behaves."
"Straight enough" may not be an issue either depending on the design and format of it. If all you have a "crooked timbers" then there may be a need to "modify" the log style you now build compared to what is currently there. The two contrasting styles can be brought into harmony by good design and "bridge details" between the two structures...vintage and "new traditional."
have you seen 200 yr old cottonwood houses? Or am I giving up on log construction too fast?
Yes and Yes...
Get those timbers your working treated even if with some "20 mule team borax" in a spray bottle and or powder them. Get them off the ground, and remove as much "sap wood" as you can. If you can't, then treat it. Get some photos up here (with close ups) and I might change my mind, but I think you could make these work...Especially in "log work," as they have the size, and they insulate well while still having good mass. (aka...flywheel and insulative.)
Cottonwood may not be the most "ideal" species in some ways, but it is workable if kept out of direct weather and up off the ground. I have seen old cotton wood in both Native structures and pioneer forms as well, so getting centuries of use out of them is achievable by "good application." These may still serve your needs...
I had convinced myself that these would still be an acceptable choice as long as I had good "feet" (most likely raised haha) and a good wide "hat".
Very wise and very true for just about any enduring architectural form...even one out of "Cottonwood."
#2
First "chinking" is stone, wood shakes, split sticks or staves or related work that goes between the logs, similar to "wattling" in many timber frames or in Bousillage work they are called ,
rabbits, batons, or barreaux. This "modern confusion" is an indication of the huge "disconnect" that exists in the actual
art of traditional log work.
Daubing, can be a "challenge" if not well done, but please done fear it. Whether just cobb, cobb/lime, or lime...it can be very durable in nature...It also has a huge range of finishes and modalities we can get into latter...Please understand that much that is "written" even by some "alleged experts" is very misleading and frankly just not accurate. Log work was one of the main motivations that brought me to wanting to write, as I see all types of "expert advice" (??) recommending things horrid thinks to be used as..."daubing"...(not chinking) like foam,
concrete and rubberized caucking...which is not mass produced by some chemical manufactures for the "log industry" as "good practice." Simply more "reinvention of wheels" for a system that really isn't "an improvement," but rather a way to "industrialize" a traditional method that works just fine...
I imagine you will get your "daubing formula" just right by doing some "test panels" and they will serve you well for decades...or even longer with little worry...
The log home I live in (built by someone else) is a good example of "what not to do." It is a "fitted log" kit style with "foam gasket" and they are failed in some spots. The solution..."good old oakum and
flax oil" fixed them right up!
Would I be doomed to using metal lathe, caulk and cement mortar?
Yep..."doomed" and that Cottonwood and cement would rot in less than 3 years...NEVER!!! use cements against anything you want not to rot out, as it is more a sponge than anything else...OPC cements are just "icky stuff" and the more I study and look and have to use in on (??) professional jobs the more I...despise the stuff...
Our other building style besides the obvious stick building is timber framing. As a novice professional timber framer it would be logical to go that route, but I do not like the uninsulated traditional style around here with the lathe and plaster and such.
Then go with a combination of the two styles...The work very well together and have hundreds of variable overlaps in vernacular modalities from Kubbhus to cobb...
Remember too, that modern timber frames can have "wall trusses" added to them as a framework to hold doors, window, insulation and everything else...so no reason to settle on "drafty" at all. I believe in "draft proof" breathable wall systems...and you can have that in many different infill matrix styles...Insulating with just mineral wool would serve you very well in a wall truss system over a timber frame...
Japanese Minka styles would complement an old log cabin well and love mixed species of wood and bent-crooked timbers...
Straw bale is not something I recommend anymore as the the "light cob" (aka slip straw clay infill) methods are typically much better...HOWEVER!! the exception would be if you had "wheat straw" literally at your demand...the SB is just fine if designed and facilitated well...So by all means...go with SB...You won't be disappointed unless you cover it in
chicken wire and concrete...SB is getting a very bad "rap" currently because to many folks are not doing it very well or with good designs, materials and facilitation...Light cob and SB play very well together I might add...
I do not recommend "structural straw bale to anyone just for the concerns you have...It should only be employed (in my view and reasoning) as a "infill" insulative material...
I like that you are really thinking about all this...keep it up...and don't hesitate to ask questions...
Till Later...keep thinking!
Regards,
j