Wednesday, April 25, 2007

Building with Cob: Update

I promised a week ago that I would provide an update on my garden project, and my greenhouse that will be built with cob walls. Well, a lot has happened since then (like getting my Apple TV), but I want you to know that the project is still on.

Cob Status
The status of the cob project is pretty much the same as I had left it, with one exception: I made an adobe brick! I took some of the straw from last season's grass (using a quick growing and dying grass that was slowly taking over my back yard) and combined it with a shovel full of dirt. I then used some of the rain water that I had collected for the garden, and began to mix.

The dirt in my part of West Valley is very saturated with clay. Most of it came from the original excavation of the basement and foundation of the home. But mostly, the land in that ancient lake bed is primarily clay. For those of you not familiar with the land in the Western Mountain States, we do not have a lot of top soil. Perhaps a couple inches, or less. In the case of my house, all the top soil came from the sod placed on top of the clay. As such the roots didn't get very deep, and come the drout, it killed off the majority of the lawn when watering became less frequent.

I don't regret saving water, but it did leave my back yard in a very nasty state. It also makes it difficult to have any type of garden, as it requires a huge amount of compost to get anything decently sized to grow. Hence, the reason I need a greenhouse for the Hydroponics project.

The Cob Brick
The brick formed really well, and I felt very confident in it's construction. But then I found out that the earth I used had too high a clay content. How did I know? Because it started to crack as it dried overnight. Cracking is a good sign of high clay content, and not enough sand. Well, the cracks were not extremely large, and the mixture was a bit moist, so I think I can say that it was an overall success. Particularly since I dropped the brick from about 3 feet onto a concrete surface, and it survived quite well!

So, I think I can call the cob project a success. This means that I can use the dirt in my own back yard to build my cob walls without adding anything to the mixture. I can deal with cracking (just by making a drier mixture, and fill in the cracks with more cob as they develop). It's not perfect, but it will do for the small greenhouse that I intend to build.

The Foundation Status
For those of you who have bothered to follow this project (and I commend those that do), I have previously laid down the foundation of the greenhouse in order to be sure I had enough brick to do the job. Since then, I have waited for enough personal funding to purchase some aggregate to lay under the foundation for proper drainage. Well, funds have been wanting, partly because of the unforeseen purchase of a new SDTV for the Apple TV project. But all is not lost! I just need enough aggregate to provide sufficient drainage.

In the mean time, I will be excavating a flat surface in the back, and using the excavated earth as part of the cob walls. This will mean a lot of excavation, as currently there is a drainage slope to the house (from decades of settling in the region). So the good news is that the grade will now move away from the house, saving potential flooding problems in the long run.

So, that is my current Cob status. As soon as I make more significant progress, I will make additional postings on the project. So the status is pretty much out of the R&D stage, and is now into the Prototype stage. ^_^

3 comments:

goodlikeamedicine said...

Hi Jeremy - found you by googling some cob stuff - it's brand-new to me and very exciting - did you buy any of the bestselling books about building w/ cob -and if so, which ones helped you the most? i am wanting to begin researching it more seriously and was wondering...thanks!

Jeremy Robb said...

Hello goodlikeamedicine! I'm sorry I didn't see your comment before now.

I was looking for some really good books, but as yet I have found most of my information online. Since then I have taken the basic links that I have posted throughout my Cob entries, and experimented. I have a really good block of cob that has survived two drops on the pavement. ^_^

If you are looking for more information on Cob, I would check out the Hand-Sculpted House. Keep in mind that a lot of the cob builders are fairly artsy in their approach because of it's sculpting ability. That being said, it's historical importance makes it the most fun building material I can think of. ^_^

If you have any questions, please let me know!

goodlikeamedicine said...

Jeremy, I received hand-sculpted house in the mail about a week ago now, and i am really enjoying reading it! thanks again!