Cob Re: cordwood homes

[Renewpwr at aol.com]

John,

In a message dated 97-12-01 12:10:11 EST, you write:

> Aloha,
>  
>  -----Original Message-----
>  From:	Patrick Newberry [SMTP:goshawk at gnat.net]
>  >While searching this site I saw a cordwood home. 
>  >The mortar look like cement based
>  >Do they every use cob?
>  >any other sites or information on this technique?
>  
>  I'm guessing you followed one of my links to this page:
>  
>  http://monticello.avenue.gen.va.us/Community/Environ/YellowMtn/workshop/
> cordwood/
>  
>  There is at least one book on cordwood building, by Rob Roy, called "
> Complete Book of Cordwood Masonry Housebuilding; The Earthwood Method."
 ISBN:
>  0806985909
>  
>  He used to have part of a site of his own, but last time I looked I
couldn't 
> find anything live - this was months ago, however...
>  
>  Cob Cottage Co. has used some log-ends in a building at their "home site" 
> near Cottage Grove, OR.  It is important to note that they used yew wood, 
> which if kept away from standing water will last 100's of years (most wood 
> won't last that long...).  This is by no means a cob-and-cordwood wall;
they 
> just happened to have the yew log ends handy and put some in low on the
wall 
> as an experiement and for aesthetics.  I've only read about using cement-
> based mortar with cordwood.  Cordwood in the wall would certainly reduce 
> total thermal mass compared to pure cob, and wood is not very insulative 
> either (although neither is cob...).  Those are two factors that come to
mind 
> at present.  Anybody know anything else about this?  
>  
>  John Schinnerer

Cordwood walls have about an R 30 wall. This is for an 16" thick wall
(Northen Cedar). I've seen any where from 5" for a workshop to 24" in Canada.
Some homes up there have double 24" walls (and you thought COB was labor
intensive!).

Cordword walls of course consist of 3 components, the wood, the mortor, and
the interior insulation. The wood used is as lightweight as can be found,
thus having an end-grain R value of about R 1 per inch. The walls are divided
into 1/3's. 1/3 inside mortor, 1/3 inside hardwood sawdust (in between logs),
and outside mortor. The combined effects are what the R-value is rated at.

I've left about a 100 details out, but Rob Roy has a web site and more info
can be found. I will post it if anyone is interested. In NewEngland, they
consider trees as weeds, unlike the West. There are cordwood homes in
Wisconsin that are 300 years old and in fine shape (without being built to
todays standards). Yes light wood rots very fast when wet, but can last 100's
of years when kept dry. Dense wood is avoided sense it tends to swell when it
gets wet and can crack the wall. Green wood can be used (< 6 months old).
When it shrinks, Perma Chink is stuffed in the holes. The walls a very
beautiful and look like stone from a distance. They are as strong as a stone
wall also. Personally, I like them much better than CAN walls, but they are
more labor intensive.

I am in the process of gathering the materials needed to build a cordwood
sauna. There are many popular trees in the midwest so some of the materials
are for free. Many farmers cut the edges of their fields every few years and
they can grow to good size quickly. No hardwood sawdust is around here, so
may use vermiculite or equiv.

Take Care,

Dave Knapp
Winnebago, Illinois