Author Topic: Planning a cordwood house???  (Read 3947 times)

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Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #25 on: February 18, 2018, 06:31:09 PM »
I am planning on the double wythe cordwood, I haven't decided if I want to use sawdust for insulation like I've seen used the most or fiberglass. Any other good ideas for insulation in the walls?

I was pricing out Alaskan chainsaw mills the other day, I might be able to borrow one also. If I borrow one just to cut a post and beam frame it wont be too bad. I've used one before to cut boards but that was out of some soft pine, considering I will certainly need boards for the roof and also for the floor if I put a second floor loft in, I may need to have something better come out.

A post and beam structure does sound like the way to go, the wood for posts will be harder to come by than the cordwood for walls but I do want this building over engineered, I'm picturing large posts and thick walls. The second floor loft isn't set in stone yet but if it does happen I would like some large round tree trunks for vertical and horizontal supports, I was originally thinking of round logs for the post and beams also but I think I like sharp looks of the square beams on the exterior better and I'm sure they would be easier to work with.

A second floor is a whole nother ball of wax. Would it work out to use (let me figure out how to say this) long logs horizontally that have each end tied into the cordwood wall, then put boards on those logs for a floor? That's kind of a vague description of what I'm thinking.

I do want this house to last and be very solid.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #26 on: February 18, 2018, 07:18:21 PM »
Actually I was envisioning the post and beam exposed on the interior of the ~2' thick walls, protected by the cordwood on the exterior. Still inset into the walls on the interior. In other words shorter pieces of cordwood outside the posts and beams as it wraps around them... keeping the frame dry.

If the posts have a beam on top of them, a top plate, then the log joists can be supported easily on top of that plate beam. The post and beam frame carries the loads and the cordwood is non structural infill. If there are failures in the cordwood wall that section can be knocked out and replaced easily without needing to somehow support any load bearing frame members during that process. Basically build the frame right up through roofing it, then drop back and infill it. Once under roof you are working in the dry.

 I would let the cordwood act as the bracing, with it infilling in between the posts they aren't going to rack or sway in the least. You would of course need temporary bracing of the frame until the infill is in place, X bracing across the exterior sides of the posts, removed a section at a time as you infill.

For insulation, sawdust sounds more like food for something, I suppose you could borate it also. I've seen it settle majorly when used in old buildings in the stud bays. I'm just winging ideas here, have you thought about a very lean Portland/perlite or vermiculite mix, sort of a hypertufa... not a clue what the R values would be.


Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #27 on: February 19, 2018, 09:51:11 AM »
Ok, I was thinking about the posts on the inside also, if that is the case I would like round logs for posts, but I have come across a lot of pictures of cordwood houses with square beams outside, I like the looks of that also.

I just found pictures of both examples, most cordwood pictures aren't from the inside so I can't tell how many have post and beam inside.





I'm nor familiar with portland/perlite but I will look into it. The vermiculite or something similar is a great idea, I should have thought of that.

Edit: Once I looked up perlite I know exactly what it is, I will look into R values.
« Last Edit: February 19, 2018, 10:20:29 AM by Rock Knocker »

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #28 on: February 24, 2018, 02:35:28 PM »
Well it looks like I found a good deal on 15 cords of 2 year dried white cedar with the bark still on.
« Last Edit: February 24, 2018, 03:01:33 PM by Rock Knocker »

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #29 on: February 24, 2018, 03:50:41 PM »
I'm trying to figure out roughly how much wood I am going to need.

If I have a 20'x30' footprint and 24" thick walls standing about 8' with about 25% mortar, how much wood is that. Of course there are going to be doors and window going in also but I am thinking about having around 15' of 30' raised higher to fit a loft. Also the possibility of exposed posts taking up some wall space.


Offline hpinson

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Re: Planning a cordwood house???
« Reply #30 on: February 24, 2018, 05:37:37 PM »
Perlite and Vermiculite here:

http://www.schundler.com/const.htm

Wasn't Vermiculite the material that was full of asbestos and caused so many problems when used as insulation. It is different when stabilized in concrete?

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #31 on: February 24, 2018, 06:03:23 PM »
I read something about the asbestos in vermiculite but I don't know if that has changed recently. I was leaning more towards the perlite.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #32 on: February 25, 2018, 03:53:46 AM »
It has been a long time since I remember that making construction news, I'm thinking 20+ years. Vermiculite is heat expanded mica. Asbestos is basically the gemstone tiger eye. From what I remember there was a mine that had some amount of asbestos in with the mica. A lot had been used and so there was significant remediation. That facility was shut down. One of my jobs as a kid was to pour the cores of foundation blockwork full of vermiculite. I've not messed with it since more than a bagfull or two. It is dusty but I seriously doubt there is an asbestos problem with the product now. I think you are working from old memory or reading old reports. I'm not trying to sway one way or the other just tending to dismiss what I think is unneccesary prejudice unless you are seeing something different/ more current.

A cord is 4'x4'x8' roughly. The length of the firewood would then play a big role in how much surface area is covered. If it is 16" wood it would cover roughly 100 sf, if 24 only about 64 sf. Footprint is not what you need, here square footage of wall area is. Do make sure you are talking about the same cord with the supplier, a face cord or rick is 4x8x 1 stick deep, typically firewood is 16" so a face cord is generally ~1/3 of a cord. I would not deduct for anything and then round up 10-15%.

Just as an aside, one story I've heard is that conventional stud framing evolved to be 16" on center because of that firewood length, you could split plaster lath from straight pieces of firewood.

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #33 on: February 25, 2018, 06:18:52 AM »
What I was reading about asbestos in vermiculite had to do with cleaning old vermiculite out of attics so I'm sure there is no where near the same risk now. 

I'm going with 24" thick walls. The white cedar I found is whole trees minus the limbs, dried for two years. I've got to meet the guy to see exactly what I am dealing with and work out a price, when I asked how much he had he said "about a semi trailer load around 15 cords." He is a tree guy so I am hoping he is pretty close to correct. I have no idea what cords of cedar are going for but he said he would give me a good deal for all of it, have any idea what I should  offer?

As for figuring out the amount of wood I need 25'x35' gives me 875sq. ft. A simple rectangular shape. (I wrote a different measurement earlier) A guy on another site helped a bit, with 25'x35' and 9' walls containing 25% mortar he was saying would need 13 cords.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #34 on: February 25, 2018, 08:12:10 AM »
Around here in that form in hardwood it would be worth $5-600 delivered, you unload the log trailer of the trees, in other words a piece of equipment at the site. If he is delivering on a semi trailer you need a logger's knuckleboom , large tractor with forks, all terrain forklift or similar there. His bunks you need to lift over will be around 12' tall. As firewood I wouldn't give a plug nickel for cedar but that is my prejudice living in hardwood firewood country. check craigslist etc. this isn't nicely cut and split firewood, those firewood dealer prices do not apply, this is bulk non sawtimber cleanup stuff, it is what those firewood processors buy. It has a fair market value but it is not high. Figure that all out with him it may be a completely different situation than what I just described. Do expect much higher waste for your use out of that load but it also opens up the opportunity that post material is in there as well. So I doubt it is all you need but he might be a good contact. the waste will burn as firewood so it is not really waste, you're just getting warts and all  :D

Just smushed my finger under a log on the sawmill while turning, all taped up and its about quit thumping, back to the fun  :D

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #35 on: February 25, 2018, 09:23:32 AM »
I figured it would get me real close. That 13 cord for that size house doesn't account for windows and doors ether but I was also hoping to have a slightly higher section in the rear to accommodate a loft. As for posts and beams I am still anticipating on buying them separate, but I do have access to a lot of maple trees I would love to use, the problem is that they are fresh and haven't been cut. Would I run into the same problems if I used green maple posts as I would using green wood for the cordwood? I don't know if wood shrinkage makes as big of a deal length wise.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #36 on: February 25, 2018, 01:23:15 PM »
Lengthwise shrinkage is negligible in normal wood but if inset into the wall, same shrinkage issues along the sides. Not sure what you ended up planning. The cedar is decay resistant, maple is not. Maple is an indoor wood The sapwood of all species is non durable.

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #37 on: February 25, 2018, 01:44:32 PM »
Good to know. I was thinking about have the posts inside anyways, I like the look of the posts exposed to the outside but it sounds better to have them inside.

If I use the maple I cut I will be milling it also. What size posts are recommended? I'm planning on having larger than necessary but what's the minimum? 

I will have to cut trees to start the project anyways so I suppose I could mill the beams first thing. Maybe it would be worth my effort to build a small temporary shelter for the fresh beams with a dehumidifier? I will have plenty of work to do before working with all the wood, maybe I could get them at least half way dry.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #38 on: February 26, 2018, 04:08:56 AM »
For posts in the lengths we're talking about I don't go below 6x6. A rule of thumb might be good here... posts fail in two ways, a short fat post fails in compression, by being crushed. A tall slender post fails by buckling, bowing out sideways. If an unbraced post is 1" thick for every foot of height in the least dimension then all you need to worry about is compression. To say that more simply an 8x8x8' tall isn't going to buckle it only needs to be checked for compression. As it becomes taller or more slender then buckling is also a consideration. Watch notching though. I was looking at a barn the other day where some posts are in distress. All that said posts rarely fail in our realm. Beams are where to sharpen your pencil. This is my heavy timber calc (a heavy timber is defined as 5x5 or larger);
http://timbertoolbox.com/Calcs/beamclc06b.htm
more calcs including columns (posts) here;
timbertoolbox.com
Use mixed maple unless you know you have red maple (if you do know you have red and are using that exclusively it does have higher strength values) Stick to #2 unless it is very good material and you know more about grading. Do not juice the numbers to make something work and avoid the temptation to use a bad timber, be dispassionate even if it costs you another trip to the woods, this is where failures occur most often, be honest in assessing the timbers and in your math. Holler with questions, I'll check in tonite, I probably just threw you into the deep end of the pool  :D

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #39 on: February 26, 2018, 09:28:12 AM »
I understand the buckling but the compression has me a little confused. I should worry about a short fat post being compromised by compression?  ??? Is that an issue that comes up if all the weight on the post isn't evenly distributed, and the areas with weight start compressing into the top of the post?

I was thinking of at least 10"x10" posts no taller than 9' possibly larger depending on the logs I have to work with.

I used to work in a machine shop too, I could make custom brackets and weld up anything I would need. I could possibly make some caps with holes drilled in them to mount on top of all my posts, then I could still use lag bolts to attach wood to wood but have the steel help evenly distribute weight.

Offline SouthernTier

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Re: Planning a cordwood house???
« Reply #40 on: February 26, 2018, 11:01:42 AM »
Replying only because I looked into this for a column in my design (and so Don can correct me if I am wrong).  But a short fat column won't necessarily get crushed, it's just that that is the most likely way it will fail with too high a load.  Taller columns can fail by crushing, too, but also by buckling.

Crushing just means the load exceeds the compressive strength parallel to the grain.  You can look up those values for various species here: http://www.awc.org/pdf/codes-standards/publications/nds/AWC-NDS2018-Supplement-ViewOnly-171027.pdf  Note, the listed strengths need to be modified by design value adjustment factors.  One of those, for columns, is the stability factor, which can be calculated according to section 3.7 of http://www.awc.org/pdf/codes-standards/publications/nds/AWC-NDS2018-ViewOnly-171117.pdf   That stability adjustment factor only really starts to be significant when you approach Don's rule of thumb.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #41 on: February 26, 2018, 03:44:22 PM »
well said  :) Actually when the post and beam are wood of similar strength the side grain crushing of the beam is what I check, the post end grain can bit into the beam side grain.
Your 10x10 will carry any reasonable load, it'll actually carry a pretty unreasonable one just fine...curious, checking, edit ... in mixed maple around 29,000 lbs, in red maple around 36,000 lbs. They aren't going to be an issue.

Do bear in mind we've now encroached on the exterior footprint nearly 6 feet to the inside of the posts, lay out that interior space and make sure everything fits.
« Last Edit: February 26, 2018, 06:17:55 PM by Don_P »

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #42 on: February 26, 2018, 04:09:47 PM »
Yes I was thinking about the walls and posts reaching inside quite a bit as well, this isn't a huge deal considering I can use the posts to put up shelves and work counter tops around them. I was also thinking about having the posts recessed into the walls a little ways, put up the posts and leave 16"-18" for the cordwood on the outside of the posts. I think the loss of insulation would be small but would it cause moisture issues?

I also have access to an oak tree trunk already cut down that would be a post makers dream(or nightmare cutting it). It's about 20' long and 3' across at it's smallest point, it must have grown in the middle of a well established forest because it's straight as an arrow with very little limbs cut off. I was thinking about using that if I make a loft section and decide to go with taller than 9' walls, or use it anywhere that may need a little more strength.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #43 on: February 26, 2018, 05:22:24 PM »
Or live edge slab it and build in counters, table, shelves, seating, etc. We just put a couple of big slabs in the kiln last Monday out of a similar sized red oak. They will be the office tops. There's a big crotched walnut slab in there for a table as well. The farm I'm working on now has been in that family for over a century, there is some nice timber that keeps our creative juices going.

Offline MountainDon

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Re: Planning a cordwood house???
« Reply #44 on: February 26, 2018, 05:40:05 PM »
Where's the "drool" emoticon when you need it?
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 #45 on: February 26, 2018, 05:59:36 PM »
Hopefully not too far OT for a minute. Big wood is fun. One of the guys just sent a link to a blog post he put up yesterday, at the bottom of that post it shows 3 of the walnut slabs going into the kiln. If you sit on the home page the top pic scrolls, one of those shows the other Don slabbing the big red oak out at the farm.
https://www.logjamva.com/

I don't think embedding the posts will cause a moisture problem. The cordwood would be more likely to conduct cold to the interior or to have a breach.
« Last Edit: February 26, 2018, 06:19:50 PM by Don_P »

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #46 on: February 26, 2018, 06:44:38 PM »
I just about wrung my buddies neck when he said he lost track of some burl we cut down about 5 years ago.  We cut down a chunk of birds eye maple that was around 4' and almost perfectly round and around 16' of the most burled up black walnut tree trunk I have ever seen.

He has since become a dumping ground for a couple arborists  in the area and the burl could be anywhere, it would be like finding a needle in a hay stack and it's likely covered with tons of wood.  d*

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #47 on: February 28, 2018, 01:11:12 PM »
So I've got a decent idea of wood needed for the cordwood walls, mortar and insulation.

What I have no idea about is the post and beam layout. Do you guys know any good resources to find a good layout or a good way to come up with a decent layout myself?

Right now I am planning on 25'x35' layout with 15' of the 35' raised to accommodate a loft spanning across the 25' width.

Offline Don_P

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Re: Planning a cordwood house???
« Reply #48 on: February 28, 2018, 03:55:01 PM »
Paper and pencil is a good place to start. There are many house plans on the net.
You are planning on 2 different wall heights and roof planes?
At 25' wide count on midspan support of the loft. All depending on roof structure lining that support under the ridge so you can support a ridge beam might be a good idea. The foundation needs to be thick enough to support the cordwood and posts.

Offline Rock Knocker

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Re: Planning a cordwood house???
« Reply #49 on: February 28, 2018, 04:06:47 PM »
Don't laugh too hard, I just spent a couple minutes sketching this up to get an estimate of how much wood the windows and door would displace, it's far from complete.

This is about what I would make in a perfect world, but at this stage I am trying to aim a little high even if I come short.


 

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