It was back in the 1980’s, so I don’t remember all the details. I do remember we built three of them and they were approximately 48” inside diameter. We baked bread every day in addition to some other products to feed approximately 100 volunteer staff members for a music festival. Firewood was plentiful, and the hornos were fired up at first light, around 5:00 AM. I can’t remember how long it took to warm the interior, but it got up to at least 600°F, and held enough heat to bake for several hours.
The materials to build came from the ranch where the festival was held, so there was no cost involved. This was in Texas in the summer, so we sun-baked mud bricks.
If it had been a more permanent situation, we would probably have invested in fire brick and a more permanent foundation or slab.