The ability to relocate a modular building is the basis for our mobile industry.  This is so much more important than just the simple ability to physically move structures.  A house mover can relocate your residence, but will the building be structurally the same after the move?  It will not be the same.  Think about the stress that would be applied to the walls, ceiling and floor.  All the joints would be loosened.  Site-built facilities were not engineered to be relocated.  Yes, it can be done, but the structural intergity of the building suffers.

Modular buildings are designed and engineered to be relocated.  The floor, roof and walls are constructed to withstand the rigors of transportation.  You might think that we just build rigid boxes, but actually modular buildings are constructed with engineered tolerances for movement.  The concept is the same for a tree.  Trees can withstand high winds because the limbs can move.  The ability to be flexible allows a modular building to withstand the stresses of relocation.