Underbuilding synonyms

What is another word for Underbuilding?

• substructure

  room on lower floor of building
• vault

  room on lower floor of building
• cellar

  room on lower floor of building
• storage

  room on lower floor of building
• understructure

  room on lower floor of building
• excavation
• crypt
• bottom
• furnace room
• subterranean room
• basement
• substructures
• basements
• strong room
• underground room
• subbasement
• subterrane
• lower ground floor
• substratum
• substruction
• understruction
• underpinning