Monday, July 22, 2013

Field to Fork Festival - 2013: Root Cellar Construction

As mentioned in my Field to Fork - 2013 post, I attended an all day Root Cellar Construction workshop on Friday as part of the festival. This was the first time the festival offered an additional day of half-day and all-day workshops, and I think it was a nice addition.

The Root Cellar Construction workshop was led by Daryl Pifer. I was already familiar with Daryl, as I have followed his blog about construction of his straw bale home, and attended his straw bale workshop at the Whippoorwill Festival just a week earlier. During the straw bale workshop he mentioned the root cellar he constructed for his own use, and indicated that it was built using dry stacked concrete blocks, which I was very interesting in learning about.

There were approximately ten to twelve participants in the workshop. I was very glad to see a good turnout, because when I had talked to Deborah, the festival organizer, a few months ago she told me I was the only one to pre-register up to that point. I wasn't really looking forward to building an entire root cellar as part of a two man crew.

When we arrived at the build site, we found the tools and materials waiting for us. The site had been excavated by a backhoe a couple of days before, and the block, bags of concrete, etc were all stacked nearby. After a quick round of introductions, and a summary by Daryl of the plan, we started work.

The first task was to level the base of the site, and, in a couple of spots, expand it somewhat. Since everyone was well rested and eager, this took very little time to complete. Once the base was fairly level we begin taking measurements and setting stakes in order to get a rough idea of the boundaries of the structure. Unfortunately the excavation was not large enough for the original design, so it had to be adjusted somewhat. The original plan called for interior dimensions of 8' by 6'. Instead, Daryl decided to go with exterior dimensions of 8' by 8', which actually provided more interior square footage than the initial design. Had the plan included a concrete floor and/or footers, this would have had to have been done in advance. Rather that concrete, we used gravel for the floor and as a base for the foundation.

With the stakes in place we next added several inches of gravel. With three people shoveling, two wielding buckets, and another pushing a wheelbarrow this was completed quickly. While we were moving the gravel, a couple of others were spreading them. After the workshop I was talking with the instructor and he suggested that when I build my own root cellar I might consider digging actual footers, and doing a rubble trench before adding the gravel base. I think I might very well do this, even if I only end up making it a relatively shallow footer.

With a base of gravel to work on, we next arranged the first course of block, using the stakes as guides for the position of the corners. Several rounds of measuring and adjusting were required to get everything squared up. This included measuring not only across both directions, but also measuring diagonally.

Once we had everything square, we next had to level each block. We started by levelling one corner block, then proceeded to level the next, while also ensuring it was level with the one next to it. This was a fairly time consuming process, which was made worse by the fact that no more than two people could work on it at once. Before finishing with the first course we mixed some concrete which was then poured into the holes of each block. Short, approximately 20' long, pieces of rebar were then inserted at strategic points, such as the corners, etc.

Daryl explained that if we had a concrete floor we would have used mortar on the first course of blocks, which would have made it easier to get everything level. Even though the first course was fairly level, we went ahead and used mortar on the second course to ensure everything was nice and level from that point on. Interestingly, though, we did not use mortar between the blocks, only below them. The second course went more quickly than the first, but still took a bit of time. Before we had it finished we had a couple of visitors to check on our progress, and I'm sure that, to them, it didn't look very promising.

Once we started on the third course of blocks, however, everything changed. The next two courses went up very quickly. I served as the primary block distributor, and tried to make sure the block layers had the correct block, whether a normal or corner block. There were at least two people positioning the blocks at most times, with a couple of others going behind them and ensuring the blocks were level. Sometimes leveling was as simple as turning the block around. Other times it required scraping off tiny debris from the blocks themselves, or adding a small amount of mortar.

The remaining courses of block would have gone up quickly, but after the fourth we had to stop and do another step of the process. Dry stacking concrete blocks requires the use of surface bonding cement, which helps to bind the blocks together. This gets applied to both the outside and inside surfaces. normally this would be done once the blocks were all laid, but in our situation there wasn't enough room between a couple the walls and the hillside to do this. Instead we had to work from the inside, and reach over the wall to apply the SBC to the exterior surface.

The remainder of the process was much the same as that for the third and fourth courses. After every couple of courses we would have to stop so the surface bonding cement could be applied to those hard to reach exterior walls. This continued until we had completed ten courses of block, which gave us the desired height. With the walls completed we finished applying the SBC to the other exterior walls, as well as the interior. It was while we were finishing this up that people started calling it a day.

There were still a few remaining steps that we didn't get to, but Daryl described them so at least we know how to finish up if build our own. The plan was to add additional lengths of rebar, inserted from the top, in the locations where the shorted pieces were added earlier. Those holes would then be filled with concrete, so that sections of the wall had solid codes of concrete, reinforced with rebar. Anchors were also to be mounted in this concrete, that would be used for attaching 4x4 beams around the entire top of the structure. These beams would later serve as anchor points for the above-ground pitched roof that was planned. For the blocks that did not get filled with concrete, I wonder if adding sawdust would be a good solution for adding insulation. I am considering trying this when we build our root cellar, although I may reach out to the instructor first to ask why he chose not to do this.

I made it a point to try my hand at nearly every task, so I would be sure to know how to do each step in the future. The only thing I did not try was applying the mortar for the second course of block and using it to help achieve level. I'm confident however, that I can figure that out.

I have to admit that when I first signed up for the workshop I worried that I would end up feeling like the  boys from Tom Sawyer who were tricked into paying for the opportunity to whitewash the fence. That was not the case at all, however. I actually found the work to be enjoyable, and learned a great deal. I am confident that I could build my own root cellar now. Without the hands on experience I doubt that I would have ever felt comfortable trying it on my own, even if I had plans to work from. This hands on experience alone made the workshop well worth the investment. After having completed this all day hands on workshop I am also much more likely to sign up for similar workshops at other venues. I'm probably not quite ready for a week long natural building workshop, but an all day workshop on building a cob oven or applying an earthen plaster would be something I would be interested in now. If all day workshops are offered at the 2014 Field to Fork Festival I am fairly certain I will be attending one of them.

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