Cost of an Addition in the Greater Montreal Area

  • One floor measuring 12’ x 12’ (including a semi-finished basement): costs begin at approximately $60,000, with an average of approximately $70,000
  • One floor measuring 12’ x 25’ (including a semi-finished basement): costs begin at approximately $80,000, with an average of approximately $100,000
  • Two floors measuring 12’ x 12’ (including a semi-finished basement): costs begin at approximately $90,000, with an average of approximately $110,000
  • Two floors measuring 12’ x 25’ (including a semi-finished basement): costs begin at approximately $140,000, with an average of approximately $160,000
  • Construction of a garage measuring 12’ x 25’: costs begin at approximately $70,000, with an average of approximately $80,000. Note: There is very little difference between the construction of a garage and the construction of a habitable room these days

Points to Consider That May Affect the Cost of Construction:

  • Level of complexity of the architectural integration
  • Building the addition on piles instead of a foundation will reduce the cost by approximately 10%
  • Difficulty in attaching the new construction to the existing structure
  • Work to be done on the existing building in order to complete the work
  • Access to the worksite
  • Choice and number of doors and windows
  • Fully finished basement
  • Choice of materials