Formwork, Part Two

A few months ago a commenter asked about how to make formwork that won't blow out at the bottom. Here is how we're doing it (and at the same time ensuring a wall of even thickness):

That's a 6-inch form tie, made by Simpson. There are other brands and basic appearances, but this is the general idea. To tie the form together you stick this through a small slot you've cut in the formwork.

So this afternoon that's what we did: cut little matching slots in the formwork.

First I drilled a couple of holes through the matched-up forms to make each side of the slot, then we could use the Dremel tool to cut the slot itself through a single layer. (It just wasn't long enough to do both layers at once.)

We fitted all the forms we had ready in place, with form ties. This helped us get a better idea of how we need to build out those forms as we progress. You can see that the little tabs on the tie hold the wall forms the measured distance apart. This works best when the holes are lined up with each other.

The wedge pieces slide in the holes on the sides and wedge the formwork into place. It makes a nice, tight connection. You can see in this photo that the "sleds" we made yesterday are the front of the wall formwork, with a 2x4 along each edge for reinforcement. That helps with the pressure of the concrete on the wall, as well.

Today we got several sections of the formwork put together and set in place, but we still have all the columns and a few of the odder spots to work with. We had a minor setback because Noel managed to pull a muscle in his back and will be laid up at least for a couple days with ice packs and ibuprofen. Welcome to old age!

posted by ayse on 04/17/11