Building the First Course of the Urbanite Foundation [Kitchen]

by ziggy on May 21, 2010 -- 6 comments -- Follow

urbanite-foundation01Last week, we set out to make some progress on stacking the urbanite foundation for our kitchen. There were a few things I learned from my own foundation, and a few things we wanted to do differently for this building. At first, we thought we’d want to dry stack the entire thing, but realized we would definitely benefit from some mortar, especially around the area where our giant posts will be sitting on the foundation.

I have not been super pleased with the clay/sand mortar I made for my own home, so I haven’t been pushing for a mud mortar. It wicks moisture big time and was a pretty big issue over winter and into the early spring — in those early days of spring, earthworms had managed to tunnel through the mortar into the house! (The mortar has since dried out. I think it was mostly wet from snow contact against the foundation over winter.)

Anyway, we decided we were willing to try a lime mortar, a 3:1 sand/lime mix to plug in areas around the foundation where posts will be set. I imagine we will end up mortaring most of the foundation, too. In this first course of urbanite, we made a chunky gravel/lime (3:1 gravel/lime mortar) mix to stuff cracks between pieces of concrete to fill the gaps.

We have been using some fairly giant pieces — our foundation is a whopping 24″ wide. So far, I’ve been pleased with how it’s progressed. Thankfully, we don’t have to completely worry about a level foundation. However, we are being careful to be level around those areas where the posts will sit, since we will have to create some kind of flat wooden sill for the posts to attach to.


I hope this lime mortar holds up a bit more sturdily than the mud mortar in my house. It will probably wick moisture as well (concrete wicks moisture, too, so it’s hard to avoid), but probably not as easily. The foundation will be three courses high, so we still have a ways to go!


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  • Hey Ziggy, thanks so much for this blog. I’m learning a ton!

    Did you do anything to the ground before laying down the first course? Dig a trench and fill with gravel, or scrape away the top soil? Or did they just go right on the grass?

  • Your first course looks awesome! I just finished dry stacking my foundation yesterday, and will hopefully be getting some cob on the wall in the next few days.

    I was wondering about when you clear the topsoil in the interior of the building. Do you leave the grass and soil until its time to pour the earthen floor? I’ve always seen people clear the whole site first, but I can see how having the grass around for a while would be nicer than a potentially muddy site. I’d be interested in your thoughts. Thanks!

  • Danielle: That is stunning. Is that all urbanite? It looks like it… awesome stacking! Are you happy with the stability of it all without mortar?

    I didn’t actually clear the topsoil for my house. It got compacted during building and I decided to leave it… in order to use less gravel to fill in later. Although clearing the site from the start would presumably alleviate that, but I decided to go with the slope of the land and not level the foundation or anything.

    That is sorta what we are doing for this kitchen, too, but I imagine we will clear some of the topsoil once it’s time to do more of the floor work. It does seem sorta strange to do it this way… heh.

  • Thanks! It is all urbanite. I had to do 99% of the stacking by myself, so stacking smaller pieces on their sides was a lot easier for me than the first few courses when I was trying to use all my gigantic pieces. It looks a little crazy, but the wall is totally solid, I can walk along it without the pieces moving. I’m going to post more pictures soon of the process, I kind of made an interior and exterior double wall of stacked urbanite, with pieces bridging across the gap b/t them throughout the courses.

    I find it really interesting that you didn’t level the site first, b/c when it was time for me to level the site, that was the one part that I was a bit unsure of. I didn’t quite understand why you had to level the interior, instead of just making the interior level through the leveling of the drain rock and the earthen floor. I decided to do it in the end, just b/c I wanted the clay, since I have 2 stories worth of cob ahead of me…

    Thanks for your thoughts!

  • Major Lee Barking-Madstock, retd.

    This is all truly interesting and I love your enterprise but may I ask you one small question?

    Why do you insisting upon trying to elevate recycled concrete to the status of an element or mineral by using the term ‘urbanite’?

    The only definition of that word is this:

    Pronunciation: \ˈər-bə-ˌnīt\
    Function: noun

    : a person who lives in a city

    Best wishes


  • Major: Hah! Yea, I guess it’s sorta natural building lingo to call it “urbanite”… It’s just a term, though.

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