I would love to build a fast cob house but i do not have land yet. I will be out of debt this year and then I will start saving to buy land.
I'm so glad to hear this, Shirley...and I'm working on a few ideas to help folks like you get Fast Cob into their lives even sooner! More soon...
So glad to hear from you again! I'm far past the stage of building (now in my eighty-ninth year) but I'll be happy to pass your video on...
I have grandchildren and great-grandchildren who could benefit from your expertise!
Hi Ann! What a lovely surprise to hear from you...yes, please do pass this on...my 13 year old daughter loves Fast Cobbing more than just about anything else, so hopefully your grand and great-grandchidren will, too! I didn't have the opportunity to build bike sheds or forts when I was that young, but if I had, I bet I wouldn't have had to wait until my 50s to complete our house! And the best part is that this is fun for every age! Stay well!
I will be building this Spring and with an attached greenhouse for food independance, I was wondering what you thought about doing the greenhouse in fast cob, but also adding slip form masonry so that I could make parts look like a stone building and also to add thermal mass inside with the rock as a wall. So my idea is that I make the slip forms, mix the fast cob, lay the stones against the slip form and then backfill with the fast cob. Think that would work?
Thanks for your question and ideas. I've only read about slip form masonry but it does not sound easy at all. One of the huge benefits of Fast Cob is that you can do what you are wanting to do with forms but without the forms! You could simply place the rocks on/in the wall as you build. Forms make more sense if you've got a big cement truck behind you that can just pour in quick setting concrete.
The other thought is that with Fast Cob, you are building in the thermal mass automatically. I'm guessing that you want the rocks to displace concrete to increase thermal mass to hold more heat, but rocks don't perform as well as cob in that department.
I love our greenhouse because it was quick and easy to build and performs just like you're planning for.
The only caveat with cob is that you don't want the walls to eventually connect with the ground and wick up moisture. And that's where you could use those rocks...as a good knee-high/2-3' high foundation. No forms needed and you still get the aestetic, but the building goes up much faster and easier with Fast Cob! holding all those windows in place.
Hope this helps!
I am wondering why with all of your emphasis on the disadvantage of wood that the background of your talk contains LOTS of wood, holding up the second story, the underside of the roof, and the kitchen cabinets. What else is possible for those places especially for tree depleted areas like Africa? Actually, I have seen kitchen cabinets of cob and roof of thatched material -- lovely. And, a cob bench in Senegal developed the problem of termites eating the straw inside the structure. It was on a rock base but I think some of the outer coating had cracked off from the extreme heat in Senegal. Once inside, how would one eradicate them. Also, worth mentioning is that the cob homes in England are protected from the heavy moisture by use of lime coating.
Thanks so much for your observations and comments. I actually laughed at that myself. The wood that you see all comes from the area we live in, which is abundantly wooded. Although it looks like a LOT, it really isn't.
To put a roof on a cob house, either unmilled timbers, milled lumber or metal is required for safety. Domed cob isn't safe in a rainforest or anywhere else that rains falls regularly. One day I'll experiment with a small structure that is domed by cob and roofed with metal, but until that is figured out fully, I won't risk my (or any other) family's safety.
For larger spans, I don't know, but I'm pretty confident that wood or metal is still required for thatched roofs. Thatch isn't known at all in our part of the world, and metal definitely lasts much longer. I also have hand split cedar shakes to roof two buildings, but despite the local source, they are twice the price and 10x (or more) the labour and time to install. They likely have half the lifespan of metal as well.
The kitchen cabinets are sparse in our home for now because I do indeed plan to build cabinets out of cob. But one thing at a time...
Yes, my understanding of the cob structures in England and Wales are they are usually plastered with lime. After 12 years here, my first and still unplastered building hasn't shown any signs of eroding away. But it has a 4' cedar shake overhanging roof line.
For the issue in Senegal, I wonder how much straw was used in the bench? Definitely a plaster would help prevent further problems but it's hard to suggest solutions without having seen the problem first hand. Worst case is the existing material in the bench is reused to make another...again, no waste created.
For areas without readily available wood, short spans/small buildings could allow other natural materials to be woven and used for beams. Scavenging metal could also work. I'm aware of a domed cob structure in a desert where rain never falls, but otherwise, some wood or metal is needed. Compared to a conventional wooden home, the amount of wood needed for a roof is a fraction of that used in the walls.
Again, thanks for these astute observations and excellent questions!