We are planning to build our house of cob in about three years and are doing some extended research on how to build.
We are plowing through 'a cob builderd handbook' which is an amazing book, let me tell you ;)
Now I have some questions that are left to be unanswered:
- Nobody ever mentions a foundation for inner walls, so I believe it is not necessary. But since I am not 100% sure on this,
Can somebody confirm that you do not need a foundation on inner walls?
- We would love wooden floors in our house. On Pinterest I see some cobhouses with wooden floors, but not many and none with directions on how to lay them and what the expcted difficulties will be. So if there is somebody who has wooden floors and wants to happily explain what we should pay attenion to, that would be great!
I notice that this has not been replied to in a couple of days. To be upfront, I have never built with cob. I have used concrete block. Assuming that there will be periods where the structure may be unheated in the winter, I would assume that interior walls could be subject the the effects of the ground freezing and frost heave. In any case, the weight of the wall would indicate the need for a good footing. With these two factors together, I have always errored on the side of caution.
Good decisions come from experience. Experience comes from making bad decisions. Mark Twain
As usual, "it depends." If you have a reinforced concrete slab and your interior cob walls are not too thick or tall, and not load-bearing, you should be fine. If load-bearing you obviously need footings, or a "raft" slab that is heavily reinforced.
Unless you are in a seriously cold and cloudy climate, you should be able to use passive solar, thermal mass, and insulation components to have a structure that will not freeze into the floor even if unoccupied.
I think a wood floor in a cob house would require either a basement/crawl space or a very dry climate where ground moisture is a minor concern. In a place like the Netherlands I would think a raised floor level with lots of coarse gravel or stone so that capillary water travel is prevented would be a minimum, and I would be much more comfortable with a system that allowed ventilation under the floor.
The Cob wall would need its own foundation. Extending to the top level of any wooden floor you plan to build.
The foundations will need to be excluded under doorways, so you and air can move around under the floor.
Even with a concrete slab, it would be best to have a thicker section under a cob wall.
IE at least an extra 100m thick with the mesh 50mm up from its bottom.
Wooden floors are OK, but they need ventilation under them as mentioned.
The floor would be set out exactly the same as any house with stumps, bearers and joists.
A minimum of 600m is needed so you can get under and move if repairs or new work is required.
The floor can be insulated as its being built.
John Daley Bendigo, Australia
The Enemy of progress is the hope of a perfect plan