Win a copy of The Biotime Log this week in the Permaculture forum!
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
permaculture forums growies critters building homesteading energy monies living kitchen purity ungarbage community wilderness fiber arts art permaculture artisans regional education experiences global resources the cider press projects digital market all forums
this forum made possible by our volunteer staff, including ...
master stewards:
  • Nicole Alderman
  • raven ranson
  • paul wheaton
  • Jocelyn Campbell
  • Julia Winter
garden masters:
  • Anne Miller
  • Pearl Sutton
  • thomas rubino
  • Bill Crim
  • Kim Goodwin
  • Joylynn Hardesty
  • Amit Enventres
  • Mike Jay
  • Dan Boone

Best recipe for cob?  RSS feed

Posts: 9
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
What is the best recipe for cob, mud, plaster for rocket mass heaters?
Posts: 2598
Location: Upstate NY, zone 5
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
It depends on the characteristics of the clay and other materials you have. Natural clay can be a component of soil in amounts from 0 to nearly 100%; many subsoils (not topsoil) have 10% to 25% clay and make good cob, perhaps with additives.

This quote from Green Homebuilding is appropriate:
"The reason there is no standard recipe in The Hand-Sculpted House is that there is no standard recipe."

All cob has to be mixed to use the materials on hand, testing as you go to find the best mixture. You want to end up with something like 20% clay, 80% sand (and possibly gravel), and enough straw to give tensile strength to the cob - the page mentioned says up to 10% straw by volume. If your clay soil already has a lot of sand and gravel, you might not need to add much.

You guys wanna see my fabulous new place? Or do you wanna look at this tiny ad?
Tomatoes! Ha! Anyone can grow that. Amaze your neighbors, grow your own shirt!
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!