Up and Out

We're up and out of the ground. The stem walls have been finished, except for the final detail around the column bases. Four columns were poured yesterday after a few false starts which were due to some unforseen problems. However, in the end it worked out perfectly and we now think that the remainder should be quite simple but possibly time consuming to complete.

The first issue revolved around keeping the column alignment correct. The problem started when we wanted to vibrate the concrete, which creates forces that are quite surprising. The form wants to rise up and move around if not anchored correctly. In the end, we were helped by the fact that the forms we had made were slightly too short. As a result, we had to make a small extension at the base of each set to raise the main section up to the level of the stem wall. This allowed us to position just the short extension forms and when correctly aligned, we cast a key which would then prevent the whole form from moving around. Another advantage we discovered was the the stem walls (which have been built exactly the correct width of the wall and are perfectly aligned) provided an accurate anchor point for the column formwork. So the combination of the stem walls and the column key locked the base of the formwork into position that made the remainder of the exercise very simple.

The next issue was to sort out how to brace each set of column formwork as the inclination is to lean out of plumb. We ended up using the walers and pipe clamps and cross-braced between column boxes. We also used the pipe clamps to assemble each column box and despite having 51 pipe clamps, we could have easily made use of a dozen more. We tried screwing in bracing pieces, but when the concrete was being vibrated, even these began to show signs of being too weak. In the end, we just moved pipe clamps between one column and the next. It was only during times of vibration that this additional support was required and we found the pipe clamps and mini-waler combination to be the most effective bracing mechanism.

We set and cast the corner section today. This was much easier to do especially as the adjacent column was set plump and was something we could use to anchor the corner box. With all the pipe clamps and walers in place, the structure was exceptionally rigid. Especially after the experience gained during the previous day, we were much more confident about what we were doing and had more faith in our form work and its ability to withstand the concrete and vibration.

We precast holes for the pipe clamps into the columns. This will allow us to finish them off with a bit of plaster and the evidence of the holes will vanish under some paint or cladding. I decided that this was preferable to leaving holes in our rammed earth walls which could not be fixed without the evidence of the repair being visible for eternity. The benefit of this was significant. With precast pipe clamp holes, it took two pairs of hands to set the walers. Without holes to anchor the pipe clamps, it took four pairs of hands to anchor the walers and of course there was a time issue also.

In the end, it was slower than we anticipated but we are very pleased with the finish and the ease of assembly (and disassembly) of the formwork. Although we are not even half way through making the columns, our imagination has leapt ahead of the program and we are dreaming of perfectly finished rammed earth walls nicely keyed into the columns and stem wall. It's great when things go well and even your fantasies have a happy ending.