Wednesday, November 28, 2007

tying lath

Yesterday, we got back to working on the dome. We finished tracing the dome with rebar and starting tying the metal lath to the rebar. Lath is sort of like a steel netting. Don says that the American lath is much better quality than the Mexican lath. It's one of the few items that we decided to purchase on this side of the border. It usually takes a couple of people to tie lath, but Don demonstrated how one could do it solo. He said, "sometimes you just got to use your head." Tying lath is a bit time consuming, but fairly easy. Once the lath is complete, we will stucco a concrete membrane ( ferrocement ) to make the dome stout enough to last a few centuries. Then we will layer cob ( sand, clay, straw, and water ) over the ferrocement. This is the part that is still up for discussion. I have been advised by a few experts that concrete and cob don't mix. I have received opposite advice from the locals...who have told me that the dome will not be stout enough to hold the heavy cob without a concrete membrane. The ferrocement also seals the rebar to protect it from rust. I have done alot of research online looking for a similar project, but have not found one. The worst that could happen is that the frame could bend a bit over time, but it is virtually impossible for the structure to crumble completely, as many pure adobe structures do during earthquakes. Time will tell.

With the surface area of the dome being 508 square feet, and the sheets of lath being 16 square feet, we will need about 32 sheets of lath. With each sheet of lath costing $6.50 in Alpine, this will be one of the most expensive parts of the project at $208.


Alan Reichman said...

Is this your geodome that is pictured here. Looks fascinating.

abe said...

be careful with that lathing! It is sharp!

The concrete dome will be able to hold the weight of the cob no problem, but without the cement on the metal, the metal cannot hold the weight of wet cob, and it will sag. You are doing it correctly.

trevor.reichman said...

at last...a voice of reason...from deep in the heart of mexico.