Cob lends itself to massive walls and curved forms. The space it creates feels radically different from what most of us are used to, yet it’s so familiar and seems more sheltering. You can’t tell from a photo, but the quality of light that passes through a thick wall is also quite different…notice the soft curves and illumination of the window reveals.
On a technicial note, the shelves on the left of the photo hadn’t been installed when this picture was taken but you can see the roundwood buried in the wall they will attach to. This methold of attachment was used all over the cottage with the windows, door frame, and roof framing all being anchored by such “deadmen”. Also note what the mud daubers left while the building was open and drying for the summer, quite fitting for a mud building!
I traveled back to Chapel Hill in September to help Greg coordinate the finish plaster and pour the earthen floor. We did the interior plaster in one day with a few volunteers, then the floor, and the exterior plaster the next weekend. It was a very busy week and we got a lot accomplished.
Our plaster was a mix of local clay slip (a thick suspension of nearly pure clay in water), sand, and horse manure. The ratios were something like 1:2:1/2 respectively by volume, but don’t obsess over numbers. You go by feel more than anything else and your local materials are certainly quite different. An earthen plaster should be very sandy or it will likely crack. It should not feel too sticky but should hold together in your hand. The horse manure was added for tensile strength, as it is pretty much completely fiber.
A properly finished earthen floor is hard and durable, but we decided that a partial brick floor near the door and stove would be appropriate. Aside from functioning as a sort of landing and hearth space the brick added visual and textural interest while complimenting the stone nicely.
Our mud hut even has electricity!
Pouring the earthen floor.
We mixed our material in a wheelbarrow with a hoe, although for a job of much larger size I would use a mortar mixer. We carried the mix in buckets, spread it on the subfloor and troweled the surface flat. The floor received much subsequent hard troweling as it dried over the next few days.
Greg with the last of the mix.
Once fully dry, after maybe 6 weeks, a treatment of linseed oil and beeswax will serve to harden and waterproof the floor.