"In other words the building had three strongly built usually stone walls"
TR,
I am familar with that concept. At Illiopolois, that is located between Springfield and Decatur, during WWII, Remington Rand built a "war" plant. For the most part, they assembled artillery shells of various sizes. The final assembly buildings were built around the permiter of the plant site with one weak wall as you state. Three walls and one half of the roof was made from reinforced concrete and the last wall and half of the roof was wood. I think they only suffered on fatality during the time that the plants were running. They stored the finished munitions in bunkers that constructed nearby. Once the war was over the bunkers sat empty for many years and then someone decided to grow mushrooms in them and that is what they have been since, mushroom farms. :)
FC