Author Topic: Planning a cordwood house???  (Read 5381 times)

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Offline Rock Knocker

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Planning a cordwood house???
« on: February 14, 2018, 11:15:03 AM »
Hello, I just found this site and I've got a whole list of questions about building a cabin.

I plan on building a cordwood house, I don't have plans written up yet but I would like something with right around 800sq.ft. main floor and then a loft for a main bedroom with a guest bedroom and bathroom under the loft.

My biggest questions are about wood prep and building this house to be able to hook up to electric and septic in the future. I plan on using Poplar wood for the cordwood and mostly maple for any posts and beams I may need to build a loft or other structural purposes.

I was wondering how long the wood should be dried for before starting the project or if there are any ways to speed up the drying process.

I would like the house to have a water hook up from a well and down the road worry about septic and electric but in the building process I would like to do all I can to make the septic and electric hook up as smooth as possible.

Right now I have so many questions I can hardly keep them all straight, so any advise on house/cabin building will be welcome.

I am also certainly no house designer, I have ideas in my head but getting them safely into a cabin is something else, if anyone knows if I can find small cabin designs to look up that would be great too.

And thanks for letting me on the forum, I look forward to learning a bit about building my own cabin. Thanks!

Offline MountainDon

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Re: Planning a cordwood house???
« Reply #1 on: February 14, 2018, 01:32:54 PM »
 w*

I would begin by contacting the building and zoning departments for the area you want to build in. Septic rules may be handled by the state or possibly a more local level authority. That goes for the well permit process as well. Where I am (NM) the state building department does have rules / guidelines in place for non conventional construction such as cordwood, straw bale, rammed earth and pumice concrete. Friends have done straw bale and a pumice concrete home. Whatever rules and regulations are in effect should be known before even planning much. This is a very labor intensive process so I would want to be certain about what is permitted, what is required, before spending much time on planning, preparation and construction.

Drying time will likely be a year or so. The better the wood is dried the less shrinkage you will have.

The bark is more easily removed immediately after felling the trees. The more sap that is present the better. When freshly cut the sap acts like a lubricant, after a week or two the sap acts more like glue.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #2 on: February 14, 2018, 03:58:13 PM »
Poplar can be a confusing term on the net, referring to either aspen or tulip poplar. In either case I don't believe it would be a good choice, they both rot readily and have high shrinkage. Our tulip poplar tends to open up a large seasoning check as it dries. Your mention of maple makes me guess that is the poplar you are referring to. If you have black locust or one of the cedars available I think it would do better, they are naturally decay resistant and have lower shrinkage. In my state structural wood has to be graded, something to ask the building official about in your pre construction meeting as well as how he would like to see the wiring done.

I'll add a little wood tech to expand on what Mt Don said about bark. In late spring through most of the summer the cambium, the layer of cells at the junction between bark and wood, is actively dividing. When a cambium cell divides one half of the division becomes wood, the other half becomes bark. During that season of active growth the bark "slips" and is very easily peeled. Around here that is when tulip poplar bark is harvested for siding and cherry bark is harvested for medicinal uses. Up north that is when birch bark was taken for canoes and berry baskets. It is also a time to be more careful when harvesting and moving timber in the woods because it is very easy to knock the bark off of trees if you bump them with a log. As the days shorten and the weather dries the tree growth slows and the bark is again "tight" on the tree.

I would soak the cordwood in a borate solution when debarked and still green. It has very low mammalian toxicity and will help with decay and wood eating insects. Good luck!

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #3 on: February 14, 2018, 04:57:57 PM »
Thanks for some of the tips, when I say poplar I believe what is around here in abundance is quaking aspen. The maple trees are tall and straight growing in a forest and would mostly be used for indoor structural stuff for a loft and stairs.

I've read good things about poplar for its insulation value but didn't look into bugs. There are also a lot of plantation pines growing in this area, I forget exactly what pines they are but when I looked into it last year the poplar and pines were rated high for insulation value and they are practically given away in this area, central Minnesota.

I am about to start dealing with the city and county, that's why I'm trying to get my ducks in a row.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #4 on: February 14, 2018, 07:06:30 PM »
Thanks for location, yup your poplar, or popple, is aspen. I'd bail on that, not so much for bugs but for its rapid decay. The pines are probably Red (Norway) pine, or White pine, you probably have Jack pine there as well. I'd take any of those over the aspen. The red is probably the greatest shrinkage but also the most durable of those. You can overcome lower insulation value with thickness, I'm sure you know conductivity is greatest in wood along the grain, the way you are using it, so thick walls. To be honest infiltration is probably the greater problem with cordwood construction, drafts around log movement. If you don't keep a handle on infiltration, insulation doesn't matter. Seasoning is key there. Wood in my house this time of year is bottoming out around 7-8% moisture content inside with the heat going. More like 12% outside under cover with ambient air. That is what you'll get down to in a stack under a shed roof with plenty of airflow in a year or so. Wood is always changing moisture content and so dimension in response to the relative humidity of its surroundings.

Offline hpinson

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Re: Planning a cordwood house???
« Reply #5 on: February 14, 2018, 08:07:59 PM »
Agree. Poplar or Aspen will rot, wet or dry, and disintegrate very quickly. Hopefully something more durable is available. Maple or oak (hardwoods) would be great.  Pine would be OK if you used preservative diligently - same challenges as log cabins, except you have end-grain exposed more.

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #6 on: February 14, 2018, 08:18:35 PM »
The plantation pines around here I believe are the Red pine. Good to know I should ditch the aspens. I would like to keep insulation up but if I went with maple and oak for the cordwood would I get other benefits? Or is there another particular wood I should look for? Black locust I know nothing of but I may be able to find some cedar, I may know a large plantation of them I can access in Wisconsin but to cut and haul all that may be cheaper to buy something locally.

How thick of walls would you recommend? I read 16-24" was common, I could go larger.

Edit: Just saw your post hpinson after I put this up. If I go with oak or maple how much insulation do you think I would be losing over cedar or red pine?


Offline Don_P

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Re: Planning a cordwood house???
« Reply #7 on: February 15, 2018, 03:35:20 AM »
The downside to most hardwoods is the shrinkage, or moisture related movement. That is why cordwood builders typically use softwoods. Locust is an exception due to the high extractives content, it's exposed movement is low enough that it was used for insulator pins inside the old glass telephone pole insulators. Cedar would be a good choice as well.
By maple I'm guessing red maple, which oaks do you have? Both are potential rafter material as well.


Offline hpinson

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Re: Planning a cordwood house???
« Reply #8 on: February 15, 2018, 06:54:06 AM »
Have you read any of the Rob Roy books on this type of construction?

http://cordwoodmasonry.com/books-media/

I'm pretty sure he has a lot to say on this topic. I think he is still doing workshops too.

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #9 on: February 15, 2018, 07:11:36 AM »
I haven't read any of his books yet but I did watch a couple videos he made. I will have to get some of those books ordered.

Offline kbaum

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Re: Planning a cordwood house???
« Reply #10 on: February 15, 2018, 08:15:35 AM »
Depending on your location, I would contact your local Natural Resources Conservation Service, this is a USDA agency that deals with the conservation of your land.  You can google them and find a office close to you.  They will assist you in finding a county or state forester in your area that could look at your trees and give you recommendations on the species of trees that you want to cut down and harvest for your walls.   

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #11 on: February 15, 2018, 10:19:20 AM »
I talked to the home inspector and it sounds like he will nearly be my neighbor when I build this place. They put my mind at ease some, he said there was another cordwood home in the area put up some years ago and it went through fine. I will need to have a submit a septic plan with the house plans but I will have 2 years to get the septic in, that's a significant weight off my shoulders and they are pretty lax about well and electric.

So I'm on the hunt for wood. I'm calling around looking for cedar, hardwoods are a back up and i know I can find plenty of that.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #12 on: February 15, 2018, 03:48:05 PM »
I'm assuming you mean the building inspector, a home inspector is one of those real estate inspection... sharks. Did you happen to ask him what species was used in that home. It would probably be worth visiting them and having a conversation as well.

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #13 on: February 15, 2018, 07:05:12 PM »
You are correct about the building inspector, I didn't ask him what type of wood was used, he said the building inspector before him was the one that knew more about it. And yes I am sure I will be in touch with them quite often.

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #14 on: February 15, 2018, 07:16:30 PM »
I am also curious about the wood in the cordwood walls shrinking and expanding with the moisture level. If I did build with kiln dried wood at a low moisture level would I have to worry about the wood expanding with enough force to damage the cement between the logs, like water freezing in a pipe?

Offline MountainDon

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Re: Planning a cordwood house???
« Reply #15 on: February 15, 2018, 07:48:55 PM »
Curiosity makes me ask... Other than the fact that a cordwood house can be attractive to look at, may make use of trees from one's own property, and the challenge and sense of pride of doing something different or unconventional, what is the reason for deciding on cordwood walls?  Just curious, because to myself it seems like more effort and time than I care for, as well as presenting challenges to air and weather sealing, electrical, plumbing and air movement handling runs,  and possibly more continual maintenance than other methods.  Just curious.

If at all possible it would be worth the time to be able to talk with the other cordwood builder in the area.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #16 on: February 16, 2018, 03:54:54 AM »
Wood is never completely dimensionally stable, you can witness this in doors and drawers that stick during high humidity and rattle loosely during periods of low humidity. It is always trying to reach an equilibrium moisture content with its surroundings. You have a moving material wrapped by a brittle unyielding material that has great compressive strength and zero tensile strength. If the wood expands the mortar goes into tension.

Andrew posted a short video of a beautiful cordwood home his sister built;
https://countryplans.com/smf/index.php?topic=14833.0

Getting way out there, there is a hysteresis, lagging, effect associated with that. Wood approaches the theoretical emc but never quite attains it. If you approach emc from the dry side the wood tends to be a percent or two drier than emc, if you approach it from the wet side it tends to be a percent or two wetter than emc. So, I would agree in that sense it may be a little better to start with kd wood. If the very dry wood meets moisture, say from rain or even wet mortar it is going to expand. If it starts a little too wet and dries, you will have gaps to caulk or perma-chink but the mortar is unstressed. In other words to an extent you are marrying incompatible materials. Not helping I know just stuff to think about.

From your handle, do you have stone on site? That would be a more durable wall.

Offline hpinson

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Re: Planning a cordwood house???
« Reply #17 on: February 16, 2018, 07:51:42 AM »
Don, my answer would be that it just has a certain appeal. They are interesting structures, and if done well, are nice places to live. I visited one once and thought it was just wonderful - organic and comfortable.  Lots of technical problems to surmount though, no doubt.

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #18 on: February 16, 2018, 08:05:30 AM »
The two largest factors for choosing cordwood is the fact that I can build it and it's relatively cheap. Plus it's beautiful, economic and be just what I want to live in. I have no interests in buying, working with or even living in modern building materials.

I turned 32 last month and I'm in the best shape of my life and I am self employed working with horses around the area. I'm selling my house in town and buying some acreage with nothing on it, so once I sell I am completely committed to building my own home, there's no other option. Along with working for myself I have some low paying part time jobs to cover all my bills, once I get rid of my mortgage I can leave the part time jobs and work on my house when I don't have work lined up for myself. Without a mortgage I will be able to make a very livable wage out of 10 hours of work a week, the rest of my time will be building a home.   

So while a cordwood house may be time consuming and present some unique challenges I will have the time to deal with them and figure it out, I would rather deal with these challenges than the challenges of paying a dozen different bills and running around working all over the place.

So would you say the safest way to go about building this and addressing leaks would be to use partially dried wood(not kiln dried) then let the walls settle for a season then calk or permachink around the logs or start out with kiln dried?

And about the rocks, I haven't given it much of a thought. It may be possible, about every farm field around here has a stack of boulders stacked up on one of its corners.  What kind of wall thickness would be best for around MN?
« Last Edit: February 16, 2018, 08:34:12 AM by Rock Knocker »

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #19 on: February 16, 2018, 09:19:10 AM »
I'm also trying to think outside the box a little to prevent air leaks. I used to work for a large company that built playground parts and they purchased a company that was making playground floor surfaces. Their product was rubber beads mixed with an epoxy, very durable but also flexible.

I was wondering how much something flexible like that would help to seal small gaps when the wood shrinks and expands. I would clearly need the regular cement for strength but maybe a thin layer on the inside of the wall, against the cement would help. Even if I got a whole bunch of those little foam beads that are usually pressed together to make a foam board and pressed a layer of the beads against the wet cement on the interior of the wall next to the logs.

Just thinking out loud...

Offline MountainDon

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Re: Planning a cordwood house???
« Reply #20 on: February 16, 2018, 12:08:24 PM »
The two largest factors for choosing cordwood is the fact that I can build it and it's relatively cheap. Plus it's beautiful, economic and be just what I want to live in.

Thanks. I was simply curious.  I do like the appearance but just personally balk at the amount of labor involved, and again, personally, don't feel like inventing the wheel for details like dealing with wood shrinkage, air infiltration etc.  I am no wheres close to being an expert on this.  If and whenever I can contribute an idea or thought I will.

The building my friends built with cordwood is used as a small equipment shed and a pottery hobby space. It is mostly not airtight but they did not try to make it so. The workshop room that is draft free was made that way using an air barrier and boards nailed to the walls inside.



Just because something has been done and has not failed, doesn’t mean it is good design.

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #21 on: February 16, 2018, 01:56:07 PM »
No problem asking.

While this is my my largest undertaking to date it is just the kind of project I can sink into and finish. There's also the fact that I will be homeless, living in a tent or renting until it's done so there will be plenty of incentive and like I mentioned, time.

I am open to other building options but the options I've found like straw bale or bagged dirt don't have me too interested. A traditional log home would be nice too but I think I would need more machinery to complete and I would end up with similar downfalls and less insulation. Building with boulders would be pretty neat too. Besides not worrying about shrinkage what are some pros and cons to building with rocks?

Offline NathanS

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Re: Planning a cordwood house???
« Reply #22 on: February 17, 2018, 05:13:33 AM »
A rock wall is proven to last hundreds, even thousands, of years. They will outlast even the most fancy modern poured concrete walls that rely on metal for their strength and plastic patented systems that the manufacturer says you have to use.

The problem with mortar and stone is that it has an r-value of close to zero. In cold climates that is definitely a problem.

I would want to talk to someone with candor that has lived in a cordwood house for at least a few years in a cold and wet climate. I would put a huge overhang all the way around the house. 1 story with a wrap around porch, sky lights or something to let some light in.

The mortar between the logs will undermine the r-value of the wood. You really would want to cement the outside of the logs in, and fill the middle with insulation. Rock wool insulation would probably do really well there.

Just one other piece of advice is to give yourself every chance to succeed. Building a house alone is a lot of work, mentally more than physically, and if at the end of the day I had to go back to a tent in a Minnesota winter... I'm not sure I could endure that.

I was just looking at a 5 gallon pail filled with masonry tools yesterday.. trowels, knives, mixers, floats... there could be $200 of that crap in there. Hard to budget for that stuff. Some people on the internet give the impression that their trowels are free and the mortar grows on trees. The details, amount of mortar, etc that goes into a cordwood wall would be worth calculating out. It may cost the same, marginally less, possibly more, than a typical stick framed wall.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #23 on: February 17, 2018, 11:28:00 AM »
Cordwood is similar to double wythe masonry in that there is an interior and exterior "shell" of masonry and a gap between that can be insulated. The wythes are bonded to one another periodically so that they act as a unit. Insulation is the tough part with stone masonry but pretty much the same as the mortar of cordwood there. There would be a "skin" of masonry on one or both faces with insulation in the middle of the sandwich. Uncoursed "rubblestone" needs to be a minimum of 16" thick. Massive stone walls on the interior with insulation outside of that and then whatever exterior finish was desired would provide quite a bit of thermal storage. You will need some type of foundation, that might be a good place to give stonework a try.

We've talked about walls, probably the easiest part of the structure. You will need some way to make the rest of the structure, the beams, floors, interior framing and other woodwork, if you are doing that yourself. An Alaskan chainsaw mill is about the cheapest way to get into that end of things. Slow but effective, a painfully slow way to make boards but ok for beams. I used one this past year fairly extensively, we needed to make some very large timbers for a log barn project that were beyond the capabilities of our other sawmills, we turned out up to 60' 12x12" timbers. The rafters on that were logs with one side flattened. Harvesting timber and hiring a mobile sawmill is another good way. Even though I own a mill I've called in a mobile bandmill on jobs where it made more sense.

One way to take a longer view, at 32 you are indeed at the physical prime of life. I was building this house about then. We also travelled the country building and living in a camper. Even that gets old in harsh winter. When you are building you are out all day, having somewhere to recharge is pretty important. We set up an 8x12 shack here during construction, it is now a storage building. As you build think forward perhaps 50-60 years. The ideal structure hopefully won't require high maintenance at that point. This is an opportunity to set that housing security up, while you have the abilities. One way might be a post and beam structure with cordwood infill. If the cordwood fails or fails in places hopefully the structure itself will be unaffected and repairs would be easier vs having to start over. All just stuff to think about.

Offline hpinson

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Re: Planning a cordwood house???
« Reply #24 on: February 18, 2018, 04:10:49 PM »
I seem to remember that Rob Roy was advocating the double wythe construction method you describe in a video I watched somewhat recently.

 

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