Balistata and Ram being built for eight hours and broke down a wall take several shots. During this time (shots) you can build a new wall. I think а block walls must be built for a long time +20min. You must build construction work site and then takes a certain time until fully built. Also stone wall may be required boards and rope, and for bricks wall - boards and nails. for scaffolding...

During the construction of the wall, it can be destroyed with a pickaxe until completely finished. Each stage will require a different number of blows with pickaxe