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Faster method for cordwood? slipforming?

 
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I have been researching cordwood homes, as I'll be closing on 16 acres in about a month. I want to build a cordwood home, started towards earthbag but was told it is more labor intensive than cordwood. Anyway, in my research I found a comment on reddit where someone mentioned slipforming for a faster construction. I then found an article that mentions using it for a double cordwood wall, and on the inside wall. Can someone explain in simple terms what slip forming is and if it can be used on single wall construction?

Also, bonus question, can I use stone as well as cordwood and bottles? I don't have a risk of earthquakes where I'm at.
 
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You can use any material, its a matter of looks and finishing techniques.
A slipform would be a solid plywood surface that does not flex and can be lifted as the wall grows higher.
Its purpose is to create a limit as to where the stones or cords will move too during construction.
It speeds up production considerably.
/slipform-construction-uses/185/
 
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This thread has some lovely pictures and a video to help you understand what slipforming is:

https://permies.com/t/33925/Cheaper-easier-rammed-earth-technique
 
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I am what may be politely called an "elder" now, but I built a cordwood home 25 years ago.  Interesting technique and I live in it to this day.  It is quiet as a stone inside. I must say at the outset that this method is most certainly labor intensive and "hands on".  I was fortunate to have a large number of standing dead cedar and Douglas fir trees available, and doubly fortunate to have the good sense to purchase one of the earliest Lucas swing blade mills. I still have it to this day.

Cordwood does not readily invite a slipform technique, I think.  It is difficult to build in this manner, at least with cordwood, and I can not see any advantage to complicating the process with a slip form.  Good for stone, I am sure, but look:  EVERY log round is different and will lay differently when placed.  Logs, even cut short rounds, taper.  I have read of some who seem to think a couple rows of mortar and slopping the wood into them is sufficient.  It is not.  I feel strongly that one has to have continual access to the work in progress, and much "tuning" of the placement of the wood is essential.  BOTH sides of the wall need to be addressed while building, and I cannot see how a slipform would allow that. And too, what of insulation?  The old Rob Roy book espouses a mixture of lime and sawdust between the mortar course.  I built a short low wall for an experiment and found this did not work all that well.  So..off to buy some 3" thick insulation cut into strips.  Peace of mind I suppose, but quicker overall.  Hint: the insulation "crushes and fills voids.

So, some caveats from experience:  Brace the walls, whether timber frame infill or some other approach. I cannot stress this enough. Brace, brace, brace.  

Strike the joints.  Not any different from traditional masonry, but if you do not strike the joints to tighten them up you will suffer air leaks and so on.  May not sound like a big deal until January comes along, and the wind is howling, but do not ignore this.

Put a few nails on the outboard edges of the rounds/splits to "lock" them into the mortar.  May sound dumb, but I have visited cordwood homes where this was not done, and you can literally move the wood with a sharp blow of a fist.  Which also means air leaks and insects.  Do it right, or do not do it at all...

Level and plumb... A minimum 4-foot level is your pal.  Really.  Check constantly.  Again, brace.  Check.  Repeat.  

A serious foundation is in order here.  You have no idea how heavy these walls will become, so this is the part where you overbuild.  My walls are 24 inches thick, and yes, it damned near killed me before I was done, but I put in 30 inch wide footings two feet deep with rebar.  DO NOT SCRIMP ON THE FOOTING.

Overhangs.  Mine are 4 feet wide but if you get rain or worse, blowing rain, you need serious overhangs.  Just saying.

Insects... do what you want, but I run a band of boric acid solution around the place a couple of times a year.  So far it has worked out well.

Not trying to sound negative, but build it like you want to stay there forever.  Good luck.
 
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Mike Chris wrote:I have been researching cordwood homes, as I'll be closing on 16 acres in about a month. I want to build a cordwood home, started towards earthbag but was told it is more labor intensive than cordwood. Anyway, in my research I found a comment on reddit where someone mentioned slipforming for a faster construction. I then found an article that mentions using it for a double cordwood wall, and on the inside wall. Can someone explain in simple terms what slip forming is and if it can be used on single wall construction?

Also, bonus question, can I use stone as well as cordwood and bottles? I don't have a risk of earthquakes where I'm at.



I would look into papercrete it makes very good mortar for cordwood construction. It has a long working time and it has better tensile/ductile strength than sand based mortar. The papercrete blend I would use is: Two 5-gallon buckets of paper pulp mixed thoroughly with one 92 lb bag of portland cement. Use a high speed mixer like this one, at least 3-4 minutes to completely infuse the fiber with cement.
Electric-mixer.jpg
[Thumbnail for Electric-mixer.jpg]
 
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E.L. Dunn wrote:I am what may be politely called an "elder" now, but I built a cordwood home 25 years ago.  Interesting technique and I live in it to this day.  It is quiet as a stone inside. I must say at the outset that this method is most certainly labor intensive and "hands on".  I was fortunate to have a large number of standing dead cedar and Douglas fir trees available, and doubly fortunate to have the good sense to purchase one of the earliest Lucas swing blade mills. I still have it to this day.

Cordwood does not readily invite a slipform technique, I think.  It is difficult to build in this manner, at least with cordwood, and I can not see any advantage to complicating the process with a slip form.  Good for stone, I am sure, but look:  EVERY log round is different and will lay differently when placed.  Logs, even cut short rounds, taper.  I have read of some who seem to think a couple rows of mortar and slopping the wood into them is sufficient.  It is not.  I feel strongly that one has to have continual access to the work in progress, and much "tuning" of the placement of the wood is essential.  BOTH sides of the wall need to be addressed while building, and I cannot see how a slipform would allow that. And too, what of insulation?  The old Rob Roy book espouses a mixture of lime and sawdust between the mortar course.  I built a short low wall for an experiment and found this did not work all that well.  So..off to buy some 3" thick insulation cut into strips.  Peace of mind I suppose, but quicker overall.  Hint: the insulation "crushes and fills voids.

So, some caveats from experience:  Brace the walls, whether timber frame infill or some other approach. I cannot stress this enough. Brace, brace, brace.  

Strike the joints.  Not any different from traditional masonry, but if you do not strike the joints to tighten them up you will suffer air leaks and so on.  May not sound like a big deal until January comes along, and the wind is howling, but do not ignore this.

Put a few nails on the outboard edges of the rounds/splits to "lock" them into the mortar.  May sound dumb, but I have visited cordwood homes where this was not done, and you can literally move the wood with a sharp blow of a fist.  Which also means air leaks and insects.  Do it right, or do not do it at all...

Level and plumb... A minimum 4-foot level is your pal.  Really.  Check constantly.  Again, brace.  Check.  Repeat.  

A serious foundation is in order here.  You have no idea how heavy these walls will become, so this is the part where you overbuild.  My walls are 24 inches thick, and yes, it damned near killed me before I was done, but I put in 30 inch wide footings two feet deep with rebar.  DO NOT SCRIMP ON THE FOOTING.

Overhangs.  Mine are 4 feet wide but if you get rain or worse, blowing rain, you need serious overhangs.  Just saying.

Insects... do what you want, but I run a band of boric acid solution around the place a couple of times a year.  So far it has worked out well.

Not trying to sound negative, but build it like you want to stay there forever.  Good luck.



Could you elaborate on bracing for me? I was going to use logs to frame a chicken house and do cordwood in between. Once the wall is fully built and dry does it still need bracing?
 
Dave Pennington
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E.L. Dunn wrote:I am what may be politely called an "elder" now, but I built a cordwood home 25 years ago.  Interesting technique and I live in it to this day.  It is quiet as a stone inside. I must say at the outset that this method is most certainly labor intensive and "hands on".  I was fortunate to have a large number of standing dead cedar and Douglas fir trees available, and doubly fortunate to have the good sense to purchase one of the earliest Lucas swing blade mills. I still have it to this day.

Cordwood does not readily invite a slipform technique, I think.  It is difficult to build in this manner, at least with cordwood, and I can not see any advantage to complicating the process with a slip form.  Good for stone, I am sure, but look:  EVERY log round is different and will lay differently when placed.  Logs, even cut short rounds, taper.  I have read of some who seem to think a couple rows of mortar and slopping the wood into them is sufficient.  It is not.  I feel strongly that one has to have continual access to the work in progress, and much "tuning" of the placement of the wood is essential.  BOTH sides of the wall need to be addressed while building, and I cannot see how a slipform would allow that. And too, what of insulation?  The old Rob Roy book espouses a mixture of lime and sawdust between the mortar course.  I built a short low wall for an experiment and found this did not work all that well.  So..off to buy some 3" thick insulation cut into strips.  Peace of mind I suppose, but quicker overall.  Hint: the insulation "crushes and fills voids.

So, some caveats from experience:  Brace the walls, whether timber frame infill or some other approach. I cannot stress this enough. Brace, brace, brace.  

Strike the joints.  Not any different from traditional masonry, but if you do not strike the joints to tighten them up you will suffer air leaks and so on.  May not sound like a big deal until January comes along, and the wind is howling, but do not ignore this.

Put a few nails on the outboard edges of the rounds/splits to "lock" them into the mortar.  May sound dumb, but I have visited cordwood homes where this was not done, and you can literally move the wood with a sharp blow of a fist.  Which also means air leaks and insects.  Do it right, or do not do it at all...

Level and plumb... A minimum 4-foot level is your pal.  Really.  Check constantly.  Again, brace.  Check.  Repeat.  

A serious foundation is in order here.  You have no idea how heavy these walls will become, so this is the part where you overbuild.  My walls are 24 inches thick, and yes, it damned near killed me before I was done, but I put in 30 inch wide footings two feet deep with rebar.  DO NOT SCRIMP ON THE FOOTING.

Overhangs.  Mine are 4 feet wide but if you get rain or worse, blowing rain, you need serious overhangs.  Just saying.

Insects... do what you want, but I run a band of boric acid solution around the place a couple of times a year.  So far it has worked out well.

Not trying to sound negative, but build it like you want to stay there forever.  Good luck.



I love hearing about DIY builds, especially "reality checks" from those who have actually done the work. I have one of Rob Roy's books and it informs my thoughts even though I don't use his methods very often. I have another book which describes a cordwood house made using papercrete mortar. They say it adheres to the wood better than sand/portland and it shrinks less, and I think it would likely be much easier to tuckpoint.

Your home sounds like a very cool looking house with those 4' overhangs. There's lots of reasons to make eaves that wide, but it adds a good bit of work. Getting thousands of mortar connections tight enough to block wind seems like a tall task and making a two foot deep reinforced concrete footing 30 inches wide...? That would kill most people.

Using a slip form to butt the cordwood pieces up against could perhaps save time if you're going to smooth the wall off and make it flat.

My hat is off to anyone who builds and perseveres!
 
E.L. Dunn
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I was not entirely aware of papercrete when I built-maybe it was on the horizon, or I was just standing too close to traditional methods.  I did a double timber frame using cants and 6x6 true cut lumber via the Lucas mill.  Most of my life I worked construction, so had a fair idea of what would be solid.  I used true cut lumber-a 6x6 is actually 6 inches x 6 inches, as I grew up with that and always had a dislike for "weenie wood" that was not what it was stated as.

As to bracing...  As I said originally, every length of wood has a taper to it-some more obvious than others.  Once you get going and the walls rise it is critical in my view to brace the frame or if not using a frame, at least use some sort of semi wide sheeting and brace boards.  A tie beam or two across the top will help, and I put some 45 degree braces on the top plates while building.  It may sound like overkill, but better that than coming out one morning and realizing a wall has an odd bow inward or outward.  I skimped on one wall as I got in a hurry and had to use a log skidder and some chain to pull it plumb.  And then brace the devil out of it.

Once the mortar is set, the braces come off.  As to the chicken house, brace it, but unless this thing is huge I doubt you need to get carried away with it.  Good luck and have fun with it.
 
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