Author Topic: Cordwood house with Rocket Stove  (Read 72188 times)

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jraabe

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Cordwood house with Rocket Stove
« on: January 10, 2007, 09:31:37 AM »
24' wide Cordwood house under construction in Upper Michigan. Good photos, a floorplan layout and information on their process. Go to the end of the link and then scroll up to see the building timeline.



http://home-n-stead.com/about/blog_files/category-3.html

(Thanks to Christopher - and Andrew!).
« Last Edit: January 12, 2007, 05:48:37 PM by jraabe »

glenn-k

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Re: Cordwood house with Rocket Stove
« Reply #1 on: January 10, 2007, 03:05:13 PM »
That's a cool project :)

Ernest_T._Bass

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Re: Cordwood house with Rocket Stove
« Reply #2 on: January 11, 2007, 09:28:33 AM »
Thanks! ;) It's coming along.. Slow at times, though. This has been quite the learning experience!

(Forgive the mess in the photos... Barn and storage buildings aren't coming for a year or so yet... :))

-Andrew
http://home-n-stead.com
« Last Edit: January 11, 2007, 09:30:44 AM by Ernest_T._Bass »

glenn-k

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Re: Cordwood house with Rocket Stove
« Reply #3 on: January 11, 2007, 09:34:37 AM »
Hi Andrew.  Welcome to the forum.

Can you tell us about your rocket stove performance?

Nice cordwood - Did you follow Rob Roy's writings on this?

glenn-k

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Re: Cordwood house with Rocket Stove
« Reply #4 on: January 11, 2007, 09:55:08 AM »
Rob Roy used his special mortar mix with a gap filled with lime treated sawdust for insulation.  It seems that your cob is a good choice as the shrinkage can be reworked with  clay/sand/straw chinking.  Any information you have time to provide will be appreciated.  

Don't worry about the pictures - a picture with a little building clutter around is better than no picture.  When you are under a deadline to get things done, it is not always possible to clean-up for a photo op.

Did you cut the bales of straw along the strings with a chainsaw to shorten the straw fibers?- I do that sometimes to make it easier to work with.
« Last Edit: January 11, 2007, 09:57:50 AM by glenn-k »

Ernest_T._Bass

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Re: Cordwood house with Rocket Stove
« Reply #5 on: January 11, 2007, 10:14:53 AM »
I have read lots of Rob Roy's books, including other cordwood mason's books as well. Some of our practices are heavily influenced by the cordwood "pros", but our cordwood is very different in that we are using "cob" as mortar, instead of the traditional Portland Cement mix. As far as we know, our home is the only cob cordwood with a timber frame that exists. We have also employed other natural building techniques, such as straw-clay insulation in the gable ends. (They will be finished with wood shakes next spring, BTW.)

Our cob mix is also a little different than your traditional cob, which contains a high percentage of long straw fibers for strength. We put shredded, dried horse manure in our cob for much more fine fibers. This made the cob more pliable (we like to call it "glob cob"), so that we were able to use it like mortar. We also pointed our cob like regular mortar, so we didn't need a finish coat of plaster cob.

Our rocket stove is chugging away... We are employing a small fan in the exit flue to keep a good draw going. We are hoping that once we install an insulated vertical stack we won't need the fan. I followed Ianto's dimensions as close as possible, and insulated the whole thing with a wet clay slip/sawdust mix. In hindsight, I would have insulated everything with fine ashes.. The wet sawdust-clay took forever to dry, and I'm not sure how well it insulates. I may be rebuilding the feed tube in the nearby future... The bricks we used were quite old, and are already chipping badly from the abuse. (I also have a tendency to wedge more wood in there than I ought... :)) When I do that, I plan to make the burn tunnel 2 inches shorter, and the ash pit 2 inches deeper. I'm hoping that will also help the draw a bit.

On a side note, does anyone here have experience building an insulated chimney? I need it to be tall and well insulated to help the draw, but it doesn't have to have a "class A" rating as the exhaust gasses are relatively cool. We like the idea of using well casing, and putting a larger aluminum tube around it to contain the insulation material. The only trick is going to be finding 8'' well casing...

glenn-k

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Re: Cordwood house with Rocket Stove
« Reply #6 on: January 11, 2007, 11:36:42 AM »
I would just make it up as you go, Andrew.  If you have it capped in a way to prevent moisture you could use wood ashes in a tin surround, but since you and I both know that the temperature isn't going to exceed 120 degrees - probably less you could use almost anything.  Fiberglass insulation wrapped with plastic, chicken wire and stucco would work.

Sawdust mixed with powdered lime as Rob Roy did would work if kept dry.  Wet wouldn't hurt it much but it wouldn't work well while wet. Your surround like the heat riser has could support the insulation then seal it as well as possible.  You could cob the top and put asphalt emulsion in and on it, or stucco to waterproof the annulus, then a tin cap over everything.  Run some type of braces to keep it stable.

I used well casing as I used to drill wells and have a bunch at my other place.  A good inventor needs a good junk pile.  Some famous guy said something like that.

Thanks for taking the time to share your experiences with us.

Ernest_T._Bass

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Re: Cordwood house with Rocket Stove
« Reply #7 on: January 11, 2007, 12:24:24 PM »
So, do they even make an 8'' well casing? I can get 6'' pretty easily, but I have no idea if or how available 8'' is...

I would do like you said; build up the outer layer in stages and insulate as I go. I could probably rivet aluminum flashing "rings" around the stack and caulk each one together to keep rain out. Set the whole shebang on a little frost-protected concrete footing and I should be good to go. The rocket stove's horizontal exhaust flue comes out of our floor and exits the wall about 16'' above the ground. I would like to tee into the main stack a little higher than that, though.. I don't want it to get buried in snow, and you want to leave some stack below the tee to collect soot. I know rocket stoves don't generate a lot of ash, though, so hopefully I won't have to clean the stack too often. A little door cut into the base of the stack would make ash removal a simple job..

Just kinda thinking out loud, here. :)

glenn-k

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Re: Cordwood house with Rocket Stove
« Reply #8 on: January 11, 2007, 12:34:03 PM »
They make all sizes of well casing but it may not be as popular there as here.  Call a well driller or pump company to see if you can find some damaged or used.  Stove pipe would work too.  Well casing will be a bit over sized requiring chinking the stove pipe in with cob or something similar.

Ernest_T._Bass

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Re: Cordwood house with Rocket Stove
« Reply #9 on: January 11, 2007, 03:30:14 PM »
Oversize as in greater diameter than 8''? I would think it should work fine, in that case. The hot exhaust gases are under pressure, in a sense, and will be "drawn" into a wider pipe (the path of least resistance). Maybe a wider pipe would even help the draw a bit?

glenn-k

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Re: Cordwood house with Rocket Stove
« Reply #10 on: January 11, 2007, 05:12:56 PM »
Rotary thin wall - (many times is 10 (about 1/8th inch) or 12 (thinner)gauge)- well casing is 8 5/8" OD same as standard pipe.  Standard pipe would then work out to about 8" ID.   The thinwall casing is about 8 3/8" ID.  Cable tool well casing is usually 8" OD similar to stove pipe.  Most well casing is pretty expensive unless you can get  remnants etc.    

Draw is kind of funny.  If it is warm it wants to go up, but if the cold pipe cools it, it gets a bit heavy and slows down the lighter gasses trying to get out.  For every bit of air trying to go up, a bit of air wants to go down -- like the weather.  That is why insulating the pipe will help it to draw better - less swapping places going on inside the pipe.  It will more easily keep going up and  the trading places can take place outside of the pipe - keeps things flowing smoothly.  Sometimes high pressure from wind builds up on the side of the house my  chimney is on.  In this case even a good draw is not enough and the wind blows backward down the stack.  A taller pipe will probably help me here but haven't got that far yet.  It's only an occasional problem.

The heat riser does pressurize the system a bit in the rocket stove once it is primed.  The primer heat helps the stove overcome the cool air in the chimney and get down the outside of the insulated heat riser and under the bench.  I'm sure you are aware of this but thought I would restate it so that others following this project will understand.

Did you have to deal with any inspections - building departments etc. on your project?  I see you went post and beam with infilled walls so that should satisfy any concerns they may have.  

Ernest_T._Bass

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Re: Cordwood house with Rocket Stove
« Reply #11 on: January 11, 2007, 06:55:18 PM »
We really don't have to worry about the code too much, here in the UP of MI. The inspector has been out three times during the building process and stayed for a total of about 10 minutes. Never even raised an eyebrow. Just the way I like 'em. ;)

desdawg

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Re: Cordwood house with Rocket Stove
« Reply #12 on: January 11, 2007, 07:55:18 PM »
Very nice project Andrew. A lot of thought and research before hitting the launch pad. And your workmanship looks fantastic. This is interesting to me as I have just finished reading one of Rob Roys cordwood books and am currently into a book on natural plasters so this is a very timely topic for me. Prior to these two readings I was into a book on stone masonry. I have an abundance of stone so it would be a natural for a foundation. I have been looking at different options to make best use of the available natural materials on my site. The two things I seem to be missing are a souce for sand and I don't own a manure factory.  :-/ And perhaps the biggest drawback is the time required for such labor intensive construction. On the positive side my soil has a very high clay content. And since I just finished assembling my little bandsaw mill sawdust will soon be abundant. The trees I have are smallish and would be more suitable for cordwood construction than any other form of log building. Now for my one nagging question. Do you feel like the cob will be as durable as a concrete based mortar mixture? Living 250 miles from my building site my construction time could stretch out for a couple of years and be real incremental.

glenn-k

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Re: Cordwood house with Rocket Stove
« Reply #13 on: January 11, 2007, 07:59:47 PM »
Quote
We really don't have to worry about the code too much, here in the UP of MI. The inspector has been out three times during the building process and stayed for a total of about 10 minutes. Never even raised an eyebrow. Just the way I like 'em. ;)

That is what we like to hear. :)

glenn-k

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Re: Cordwood house with Rocket Stove
« Reply #14 on: January 11, 2007, 08:06:16 PM »
If you do a post and beam structure and get the roof on first the cob is pretty durable.  Around 4 to 7% cement will stabilize it but it's not as nice to work with and is not really cob then but more of a cement stabilized adobe or soil cement.  Works great for rammed earth.  This small amount of cement makes the difference between washing away or not.  Testing samples is in order.  Basic mix for most earth building is 30% clay 70% sand and aggregate and straw to taste.  More clay - more straw.  A good roof overhang protects it pretty well.

Ernest_T._Bass

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Re: Cordwood house with Rocket Stove
« Reply #15 on: January 11, 2007, 08:26:05 PM »
Quote
Very nice project Andrew. A lot of thought and research before hitting the launch pad. And your workmanship looks fantastic. This is interesting to me as I have just finished reading one of Rob Roys cordwood books and am currently into a book on natural plasters so this is a very timely topic for me. Prior to these two readings I was into a book on stone masonry. I have an abundance of stone so it would be a natural for a foundation. I have been looking at different options to make best use of the available natural materials on my site. The two things I seem to be missing are a souce for sand and I don't own a manure factory.  :-/ And perhaps the biggest drawback is the time required for such labor intensive construction. On the positive side my soil has a very high clay content. And since I just finished assembling my little bandsaw mill sawdust will soon be abundant. The trees I have are smallish and would be more suitable for cordwood construction than any other form of log building. Now for my one nagging question. Do you feel like the cob will be as durable as a concrete based mortar mixture? Living 250 miles from my building site my construction time could stretch out for a couple of years and be real incremental.

Well, to tell you the truth, my mom is the big cob lover in our family. I was very skeptical about it's durability, but she wouldn't hear of any other mix. So, from what I've observed... The cob isn't going to go anywhere unless you get a monsoon or tear at it when it's wet. It is quite vulnerable on the surface when thoroughly soaked, as we have not waterproofed it yet, but it doesn't appear to be washing away. We have 2 ft. overhangs on the gables, and 3 ft. on the back (north) side of the house, with a 6' porch in front.

We're going to let the logs (Aspen) dry thoroughly before treating the cob with anything, to making repairing shrinkage gaps easier. Right now we are looking into Hemp oil for finishing the cob and wood.. It's supposed to be better than Linseed oil, but it takes a long time to dry since it's not boiled.
« Last Edit: January 11, 2007, 08:28:52 PM by Ernest_T._Bass »

glenn-k

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Re: Cordwood house with Rocket Stove
« Reply #16 on: January 12, 2007, 04:49:18 AM »
I read a quote somewhere from a guy in England I believe who said that the weather wouldn't affect the cob more than about 1/4 inch deep  - provided it had a good hat and shoes.  Rocks on the bottom or other solid foundation keep water from drawing up into the cob.  A good roof stops it from going down through the top.

jraabe

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Re: Cordwood house with Rocket Stove
« Reply #17 on: January 12, 2007, 05:53:51 PM »
Andrew:

We've had problems in the wet Pacific NW with Linseed oil treatment on wood siding. Seems the mildew loves the stuff and turns it green and/or black depending on the season and sun exposure. I expect an organic material like hemp oil would also be tasty but don't know if your climate has the same issues or not.

A very interesting project you have there and thanks for letting us in on your process.

desdawg

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Re: Cordwood house with Rocket Stove
« Reply #18 on: January 12, 2007, 09:43:10 PM »
Thanks Andrew. I hope you keep posting as I am interested in following along. Eliminating the need for commercially produced mortar would make it almost perfect.

glenn-k

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Re: Cordwood house with Rocket Stove
« Reply #19 on: January 13, 2007, 05:24:16 AM »
I think DEFY would work for both the wood and to protect the cob, but then you are getting into a commercially produced product.  It does not support fungal growth and is a 98% waterproofer.  It is not made for cob but is pretty hard to get off of anything it hits.  

Another thing is styrofoam dissolved in laquer thinner.  I haven't tried it but it leaves a waterproof clear plastic coating - works on cob and would work on the wood - the laquer thinner dissipates soon.   Once again - probably a material you are trying to stay away from but it does recycle styrofoam into something usable.  Reported to me by Shelley.


desdawg

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Re: Cordwood house with Rocket Stove
« Reply #20 on: January 13, 2007, 06:57:30 AM »
I am not a green purist or anything like that. I just wanted to maximize my available resources. I don't want to have a manure factory to take care of though.  ;D Might have to borrow the byproduct from someone else. And I did find an old state gravel pit that has some sand. The pit was used during the construction of I-40. I think I could smuggle some sand out of there without any repercussions. Quick trip with the Bobcat and dump truck.

Ernest_T._Bass

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Re: Cordwood house with Rocket Stove
« Reply #21 on: January 13, 2007, 02:06:12 PM »
Quote
I think DEFY would work for both the wood and to protect the cob, but then you are getting into a commercially produced product.  It does not support fungal growth and is a 98% waterproofer.  It is not made for cob but is pretty hard to get off of anything it hits.  

Another thing is styrofoam dissolved in laquer thinner.  I haven't tried it but it leaves a waterproof clear plastic coating - works on cob and would work on the wood - the laquer thinner dissipates soon.   Once again - probably a material you are trying to stay away from but it does recycle styrofoam into something usable.  Reported to me by Shelley.


That styrofoam sealer is an interesting idea... However, we definitely do not want to use a "sealer" on the walls. One of the great beauties of cordwood and cob is it's ability to breath. It keeps the air healthy in your home, and wicks out excessive moisture. This is why the log ends don't rot. They dry out extremely fast after getting wet, as moisture travels twice as fast along the grain of the log, rather than against it (such as in a conventional log home). If you essentially coated the house in plastic, it would rot from the inside out.

I don't think our climate would be considered near as moist as the Pacific NW, so I hope the oil treatment will work ok... The downside to the oil is that it will need to be reapplied in time, but I don't think there are any natural alternatives.

Perma-Chink manufactures a breathable sealer that might work and provide better weather protection than the oil, but I think that we will be staying away from petroleum based products..

glenn-k

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Re: Cordwood house with Rocket Stove
« Reply #22 on: January 13, 2007, 03:42:22 PM »
Yes - the plastic may work in places - not in others.  We like to seal our cob benchs in the conversation pit with Quickcrete Cure and Seal - gives it a quick fairly cheap shine and keeps our clothes clean.  We used linseed oil on the entrance cob floor.  We really like that floor.

A friend who sawed his own lumber for his house uses a garden sprayer (Hudson type) to apply his linseed oil.

Thanks for the theory on the moisture movement through the log ends, Andrew - I hadn't picked that up before.
« Last Edit: January 13, 2007, 03:42:49 PM by glenn-k »

Amanda_931

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Re: Cordwood house with Rocket Stove
« Reply #23 on: January 16, 2007, 05:36:38 PM »
I've had linseed oil coated wood turn black, especially on the equator-ward (south in my case) end.  I'd kind of figured it for some sort of UV reaction, because a local deck builder can go on and on (and on) about getting sealant on his decks that has UV protection.

But John could easily be right--the wood is also black right up at the roof--more or less in the shade, as is the north (polar) end.

jwv

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Re: Cordwood house with Rocket Stove
« Reply #24 on: January 24, 2007, 03:42:08 PM »
DesDawg, I would think in your area you could use cob without any additives as long as it has a "good hat and shoes" as Glenn stated.  I would also leave the straw as long as possible to knead the layers together.

Here are a couple of new (to me)cob structures in So AZ

http://web.mac.com/camelboo/iWeb/Natural_Building/Peg%26Maryscob.html

http://cobstudio.blogspot.com/

Ernest T. (the best rock-thrower in the county) is my all-time favorite character on Andy Griffith!  Your house is beautiful.

Judy