My current design is basically a log/timber framed structure approx. 20'x36', 2 story, with a sod roof and earthen floor. I would like to do a form of the raised earth foundations that Jay has advocated for in other posts. I will just section my subjects in paragraphs to try to keep from getting too confusing:
FOUNDATION: In my area, as with much of Ohio, hardwood log cabins were the norm, then timber frame, then stick builds. The home I live in is an 1811 18'x18', 1 1/2 story log cabin on stone feet at the corners. The floor is typical wood planks on joists. My problem with doing this in my new build is both practically and philosophically driven. Number one, they are cold unless insulated. I don't see a natural, non-synthetic, affordable insulation option other than straw or some other fiber, and I don't trust them to not create mold, rot issues under there. Also, I'm guessing the raccoons and other animals will simply tear it all up and make it ineffective in short order. Number two, I love earthen floors in general. Their feel, look and "connectedness" with the ground is what I am after. I also feel that although they are not technically insulated, their mass along with their tendency to stay the general 55 degrees or whatever would make it warmer than an uninsulated wood plank floor. I plan to use rot-resistant wood sill beams to surround and "hold together" the earth floor, then build up from there (most likely a mix of log and timber framed crucks.
My main struggle is that I want to keep the floor the same level as grade. I do not want it raised. I want the floor and the surrounding ground outside my front door to be all but seamless if possible. My possible building materials are wood, limestone from the local quarry (which I would love to forgo, but will give in to long before giving in to a synthetic vapor/moisture barrier), clay, fibers (straw is the easiest, as my family farms). My building site is next to the original cabin in which we currently live. It is a high spot with no danger of flooding or water buildup. Jay, (or anyone else), could I realistically do a raised earth-style foundation without it being raised? I've been trying to come up with different configurations using stone to not only stop moisture from coming up from below the floor, but also from the sides. And, although I know its putting the sill timbers in a more vulnerable position, I would like them to surround the earthen floor instead of stone, thus, making the top of the sill plates level with the floor and with grade. Mainly this would be for its insulative affect that the wood would have compared to using stone to surround the floor. Would it be as simple as using gravel between the sill plates and the surrounding earth? Or possible flatish stones pointed up to surround the sill timbers? Is there another natural option that I am missing to help keep the sill timbers dry in this position? Is it just not worth it to have the timbers below grade for the added insulating affect they will have anyways? Am I stupid for not just raising the darn thing off the ground like Jay's postings have illustrated haha?
The library computer is about to kick my off so I will have to end this one. I'll probably just sign back on and make a separate posting to ask about the earth roof design issues. Thanks in advance
I would be glad to assist you. I would love if you could email me directly and also start a post (with photos) of and about your project!
For now I will hit the highlight of your questions, and try to be as helpful as I can...
I am a novice timber framer in Central Ohio (I have 3 structures under my belt, along with a current 1200 sq. ft. cabin mid construction) that is planning to begin construction of my families future home this summer/fall...My current design is basically a log/timber framed structure approx. 20'x36', 2 story, with a sod roof and earthen floor. I would like to do a form of the raised earth foundations that Jay has advocated for in other posts.
Sounds very nice and quite viable for a traditional style structure reminiscent of many "Kubbhus" and "Piece sur Piece" vernacular structures...
I would suggest doing a localized cost analysis of a "shake" or "metal standing seam" roof and wood floor compared to the cost and effort of a "sod roof" and "earthen floor." The first can be aesthetically pleasing but lead to issues down the road that could be avoided and the earthen floors are not always the most economical if the fiscal comparison are made. I am very open to both if well thought through and planned for...
Your 1811 cabin is a great "model" of a vernacular style that is excellent to copy and/or augment with timber framing. As for being "cold" (I currently live in a log cabin in Vermont) that is a matter of "proper design" and "detailing." With both these performed properly "log cabins" need not be cold or inefficient.
If going with a "modern insulation" that is also historical, a reclaimed material, and with a proven history going back over 100 years...I recommend "mineral wool" board and/or batt that we have discussed here on Permies several times. For a "diy" material that is natural, my first choice has become "light cobb" slip forming with sawdust, wood chip, or straw, according to what is available. Both mineral wools and the light cobb can work together in a system matrix to very excellent effect.
Pest and Animal proofing is actually one of my "old jobs" for the state of Connecticut as a "State Supervisor" in "Pest and Wildlife Control." This is a vast subject in itself but should be a concern. Well designed and built homes...with the proper holistic management plan will not suffer these creature invasion accept in a limited seasonal periodic event. More on this when I see a CAD model or blue prints.
"Heat" escapes the "floor" least of all and this is why earthen floors can work. We can get into details of them later as I get to see details of the building. Some systems work, while many will fail if not facilitated properly give time and/or be a nightmare to maintain. Have you read the Tataki 三和土 post yet??
My main struggle is that I want to keep the floor the same level as grade... I do not want it raised..I want the floor and the surrounding ground outside my front door to be all but seamless if possible...
Let me be clear..."zero entry" is a modern concept and 99% of them are ill fated and poorly designed, but can be achieved with the "raised earth concept." Comparatively these are much more "expensive" (time and $$) to achieve compared to "post and plinth" systems alone. Many of these "zero entries" may seem like a "great idea" but in comparison to other factors and aspects of "good design" they simply lead to just too many issues and challenges over time. Structure need good ventilation all around them, even if on a solid earthen dais...This can't happen if the architecture is "at grade." Now with a raised podii (aka kan or dais) they can be made to work well but are much more expensive in time, labor and/or fiscal assets to achieve compared to the many vernacular designs that are at minimum 300 mm off grade. In one the "veranda" or "porch area" is made usually of wood, and in the other form (i.e.dais) it is a great deal of time and material effort with stone and earth building that must take place...If that is acceptable then a traditional "zero entry" can be achieved with a podii or dais system as outline in a "raised earth foundation." When I see a design elevation blue print or CAD, I can be of more assistance.
Jay, (or anyone else), could I realistically do a raised earth-style foundation without it being raised?
Simple reply...probably not. Raised earth systems are just that...stone and earth raised off grade...even if the grade is raised itself. Having a "raised site" is kind of the best spot to build to begin with whether building a "post and plinth" (aka socle) foundation or a Raised Earth podii foundation...
"Wanting" (even really badly) to do something a certain way doesn't change its illogic. This is why structure that endure historically are built the way they are. Stone and earth...at grade...go together...wood sill at grade simply does not. Can it be "made to work" ...yes...but the questions is whether the cost is worth the effort and potential risk compared to wiser and more traditional systems of design.
Mainly this would be for its insulative affect that the wood would have compared to using stone to surround the floor. Would it be as simple as using gravel between the sill plates and the surrounding earth?
This is one system but is not as simplistic in application as it is in concept...there is great effort and toil to make this work, so be warn that if this is the goal...we can "make it work"...but it will not be the most prudent in effort or design.
Is it just not worth it to have the timbers below grade for the added insulating affect they will have anyways? Am I stupid for not just raising the darn thing off the ground like Jay's postings have illustrated haha?
Lets not give up yet "making it work." Send me an email and get me a CAD to review and I will see what I can "pull out of the hat" that may facilitate your plans. I would really like to see you achieve your goals and this "zero entry" concept is very popular in some areas. I can say flatly and honestly it will never be easier than other vernacular systems of design.
thanks for checking in. I tried emailing you through some auxiliary website (i forget what it was), but I suspect it didn't go through. Can I just PM you? I'm guessing thats the logical thing to do. So I haven't followed up because I am going through some rethinking.
As far as the foundation being level with grade, I have some ideas, but am leaning more and more toward just raising it like i know is the smart thing to do.
But the big thing I'm going back and forth with in my head now is more about the basic construction. I had decided that I would go the traditional hewn log house route. As I mentioned, the original part of our house is an 1811 cabin of white oak. The fact that it is still here and more or less sound (one corner has sunk but to be expected since it is an 18x18, 1 and 1/2 story, with only foundation stones at the corners, on clay) means that it is a proven construction of course. We will be building our new house next door to it, about 16' away, connected by a breezeway. So, it of course would be asthetically logical and pleasing to build the same.
However, there are some problems and/or questions I have:
#1. I have 30 acres of wood, 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). So, my only other option besides buying them in, is to harvest them from the farm I grew up on 30 miles away. But, the only tree that fits the bill there are tall, somewhat straight eastern cottonwoods that grew very fast. I had convinced myself that these would still be an exceptable choice as long as I had good "feet" (most likely raised haha) and a good wide "hat". But now, after hewing a few and feeling how soft the sapwood is and seeing the bugs go crazy over them sitting in that field, I just don't feel good about it. I need this to be the only house I build for us. Am I right? have you seen 200 yr old cottonwood houses? Or am I giving up on log construction too fast?
#2. The chinking. Everything I have read convinces me that the chinking will be a constant problem. As I said in the original post, I have no intentions of giving in to conventional modern materials. If a natural, traditional chinking just needed to be dressed up once a yr or so, thats ok for me. I expect to and look forward to having an ongoing connection to our house and other structures we build. However, I do not believe I would be ok with constantly having drafts coming in and chinking crumbling and falling out a month or two after I repair it. I don't want to constantly be "fighting" to keep our house reasonably comfortable. I know you live in a log home, what is your experience? Would I be doomed to using metal lathe, caulk and cement mortar?
What do you think? 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. I fear straw bale infill, but i have access to unlimited free bales (my family bales wheat straw), so I havent talked myself out of it yet. The light straw clay seems like a more proven form, which goes well with my native materials: timber frame worthy hardwoods, straw and clay. And the more I maul over this, I think I would rather build something where the frame and insulating parts of the house are somewhat seperate. If the straw bale or light clay straw is ruined and needs to be replaced in 50 years, the frame will still be there going strong if I kept a good roof over and foundation under it. If the log walls rot, the house is doomed. I might as well burn it down and start again. Any thoughts on that logic?
And please, anyone chime in, I didn't mean this to be exclusively for Jay.
thanks Jay and anyone else who can help straighten me out haha,
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."
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!