[Cob] strawbale, geodesic domes, and igloos

[GlobalCirclenet]

Thank you for a very understandable explanation from actual experience. I
was basing my comment on traditional cob rather than thin coats made with
shorter straw. I took all cob to be the usual foot mixing and stomping
straw into mud, and throwing it against the wall (basically). I hope people
who try to cob strawbale know to make it different from the usual mix. It
would seem cob used that way  would be more of an earthen plaster than cob.

paul at largocreekfarms.com
http://medicinehill.net
*********** REPLY SEPARATOR  ***********

On 7/22/2004 at 11:10 PM Shannon C. Dealy wrote:

>On Thu, 22 Jul 2004, GlobalCirclenet wrote:
>
>[snip]
>> strawbale with cob. It's clearly about thin coats of plaster, not cob at
>> all. It recommends earthen plasters. The difference is significant
>because
>> cob is not the same as earthen or any other kind of plaster. Plaster is
>> applied in very thin coats, esp the first coat to "key" into the straw.
>
>That is one recommendation, there are many approaches to plastering bales,
>cob works perfectly well, and "earthen plasters" are in fact simply cob or
>close enough variations as makes no difference (cob is a particular type
>of mixture, not how thick you apply it).  I have personally applied
>cob type plasters in both thick (a couple inches) and thin coats to straw
>bales, dating back about nine years, and have worked with many people
>who have far more experience than I do.  There are no problems with doing
>this, though it might be a concern if it were done in cooler weather when
>the drying time might be slow enough to cause problems (say mid-October to
>mid-April here in the Willamette valley of Oregon).  The primary reason to
>use thin coats is that multiple thin coats will finish drying faster than
>one thick coat, and it will take less plaster to reach a fine crack free
>finish layer.  Of course if you want more thermal mass, are working in
>warmer dry weather, and it will dry faster than you will be ready for the
>next coat, it takes alot less work to go with the single two inch layer
>for a base coat.
>
>[snip]
>> afford the contractor liability. Most likely because cob has to be much
>> thicker than plaster, and takes longer to dry, and releases too much
>> moisture into the straw.
>> Plain cob is a safer and much more interesting material.  Sealing straw
>> properly against moisture means paying professionals for a lot of labor
>> plastering. You simply cannot risk health problems later by
experimenting
>> or learning on the job. It is not for first time do it yourselfers.
>Whoever
>> said strawbale was fast, easy, or cheap forgot about the horrendous job
>of
>> plastering completely.
>
>Cob is not defined by thickness, and does not have to be "thick", it is
>perfectly safe to use on bales and has been widely used for this purpose.
>I have made cob plasters using EXACTLY the same mixture that went into cob
>walls, the only difference being that the sand and clay were screened to
>remove lumps and the straw was shorter (same total volume of straw, just
>shorter) though many people use full length straw these days in plasters.
>Adding extra water may be desirable in many cases to make the mix more
>workable, particularly with longer straw, but this depends on
>circumstances and is not always a necessity.
>
>As far as straw bale being:
>
>   fast - it takes roughly the same amount of time as wood frame
>          construction to do a comparable structure, which isn't fast but
>          is certainly faster than cob.  Much faster bale structures have
>          been built (one small one that I took part in was done in a day
>          excluding plaster), but these generally are not designed as full
>          blown houses.
>
>   easy - it isn't particularly difficult for load bearing walls, for
>          bale infill, someone needs more serious carpentry skills.
>
>   cheap - depends on the design, availability of materials, and how much
>          labor you do yourself.  Like cob it can range from $0 with lots
>          of personal labor, on up to as much as you would like to spend
>          and beyond.
>
>It is important to be careful not to read more into what people say on
>the internet than is really there, as sometimes the information is not
>well worded, or poorly thought out, depending on the circumstances under
>which the person wrote it.  I have personally made some glaring errors in
>postings over the years, and if someone read just that posting and not the
>follow up where the error was corrected, they might come to the wrong
>conclusions.  There is also another danger in that some people post
>opinions based on other people's opinions, which may in turn be based on
>other people's opinions, etc. and there may not be any actual experience
>behind the statements.  I cannot say if either of the above apply to the
>source for your statements, but there is lots of real world experience out
>there that says cob plasters on bales is just fine, and it has been done
>for at least 9 years that I am aware of, so problems in the buildings I
>worked on should have shown up long ago.
>
>
>Shannon C. Dealy      |               DeaTech Research Inc.
>dealy at deatech.com     |          - Custom Software Development -
>                      |    Embedded Systems, Real-time, Device Drivers
>Phone: (800) 467-5820 | Networking, Scientific & Engineering Applications
>   or: (541) 929-4089 |                  www.deatech.com
>
>
>_______________________________________________
>Coblist mailing list
>Coblist at deatech.com
>http://www.deatech.com/mailman/listinfo/coblist