Buildings may not be built inside other buildings, with the exception of towers. Up to six towers may be built inside a castle.
Effort is in worker-days.
The builder must know the required skill, have at least three workers, and possess at least one-fifth of the necessary construction materials in his inventory. The builder and his workers will be placed inside the new structure. The remaining construction materials are paid as work on the structure progresses. Construction halts if the builder runs out of materials. The building is completed when the required number of worker-days is invested in construction.