Weekend Project 2: Preparing for the Foundation

Posted on

This weekend was quite the weekend, testing the project in an administrative and practical level. How so? Well, I ran into a little snag, which prompted some push-back from my wife.

In order to have a successful cob building, you need to have a solid foundation. Most cob builders use local stone that is fairly flat on both sides, and then dry lay them into place. Well, I can't do that. The stone that is native to West Valley City, or at least the majority of West Valley, is all round stone. This is because we sit in the basin of an ancient lake (Lake Bonneville), and as such have stones that are rounded.

Now, I could just cut the stone into flat shapes, and then work with it that way. But that would be even more time consuming, and I would like to get this project under way. That, and I don't know how to accurately cut stone without expensive tools. So, we took a trip to the local Lowes to estimate various foundation options.

We checked out the flagstone (perfect for a stone foundation), concrete costs (the foundation would be roughly 48 cubic feet of concrete), the cost of brick, and even checked out the cost of cinder block, just in case I got that desperate. All (except for the cinder block) came to about $100 to $200 for the overall foundation of roughly 48 cubic feet. Because of the cost, my wife began to push back on the whole project. I became concerned, and I don't mind saying a little desperate, wondering what I could do in order to keep the project alive.

Now, why 48 cubic feet? Because that is how much a one foot by one foot foundation would be for a 10 foot by 14 foot building. The foundation should be at least 10 inches from the ground if it were to be properly constructed, and one foot made it easier to calculate. Then I started to think, why do I need such a high foundation?

The principle of the 10 inch foundation is based on the need for two things: flooding concerns, and insect control. If there were a flood situation, a high stone foundation would keep the flood from weakening the walls of the cob building. Very important, and practical. But, as I live in a semi-arid region, flooding isn't that big of a concern. Why, even back in the great floods of 1983 when Downtown Salt Lake City had rivers instead of streets, there wasn't a flood concern for the house I am currently in.

Insect control is another matter. Insects are notorious for building nests where they can, whether it be a wood or cob home. In this case, even dry-laying stone doesn't prevent insects, as they can easily navigate between the stones. Most cob builders will place mesh down to keep the insects from burrowing into the walls. Thats easily done with a smaller foundation, as well as a larger foundation.

So, with these two reasons for a taller foundation already resolved, I found a way to save the project: shrink down the foundation. And, because I don't need a larger foundation, I can use the existing bricks I have for the garden. Here is how it has played out so far:

I cleared out the paving bricks from the back yard that was set for a chess board. I'll place them back later, I'm sure, but for right now, I wanted the space to see just how big the new greenhouse would be. I have to say that I'm quite happy with the results! I then set down paving bricks, as they are all one foot by one foot by 2 inches, to see how the interior will play out. Looks nice!


Then I started laying the bricks that I currently have, to see how they will be placed. I calculated that I would need a total of 264 bricks, and I currently have 229. That means I only need about 35 more bricks, which brings the cost down considerably. Of course, I may be able to bring it down even more by using some of the other paving stones around, but putting them in the back of the building where there would be little shown.

So, I have brought the cost of the foundation down, which was roughly 70% of the total cost of the project. All that is left now is to level out the ground (perhaps with sand, or just cutting down the ground itself), digging out a central drainage ditch for heavy rains (should there be any), and then setting down the foundation as a final setting. I hope to get a lot of the leveling off done this week (maybe Thursday and Friday), so that I can dig the trench, lay down some pea gravel for more drainage, and then set down the foundation. At that point, I just need to start mixing the cob, get the wooden framing up for the greenhouse slats, and then put it all together.

Once that is done, I'm going to start putting together the hydroponic system that I want to use for the plants. I'm really excited about that project, because the basic system should be done by June (if all goes well), and in the mean time I can start some of the smaller hydroponic sessions for the traditional out-door plantings.

More on that later, once I have the whole project outlined, but I'm excited to think that by this winter, I can still grow some fresh greens and veggies for year-round consumption.