Build a Duplex Cost

How much does it cost to build a duplex?

This is a project different from an apartment building or a condo due to the fact that most duplexes are smaller and contain a single story - and many are developed within pre-existing structures as well. While the U.S. Energy Information Administration states that the average apartment is 861 square feet, the average duplex runs at 900 square feet. A duplex can appear in a free-standing structure of two or more dwellings, but these will not have common walls, and will only touch at floors or ceilings. This is the reason that a duplex building tends to be smaller in total size than an apartment building.

For the purpose of this discussion we will look at a standard duplex containing four dwellings 900 square feet each. This translates to more than 4000 square feet of construction, and assumes a "footprint" of approximately 30'x60' for the building.

The building of a duplex building would never be a "DIY" project and requires a knowledgeable contractor, an architect, a team of subcontractors, and a cooperative developer/owner to get the job done quickly.

According to Hawkins Research, Inc., the typical costs for the building of a duplex complex of four units would include:

  • With mid-range materials, a normal foundation with full and finished basement, efficient doors and windows, all appliances, and "turnkey" finishing the structure would require an average of $138,500 per unit to complete. This does not include acquisition of the building lot or site.
  • The above figures place this construction at a $126 per square foot cost, though national averages stand between $85 to $125. This pricing structure assumes that carpenters, masons and excavators charge an average of $70 per hour, electricians between $65 to $85 per hour, plumbers between $45 and $65 per hour, and painters between $20 and $35 per hour.
  • This sort of building, however, would not come in at the lower cost of $85 per square foot due simply to the excessive amount of construction required. A two-story unit of wooden and masonry construction with four duplex units would run roughly $552,000 in total costs. This excludes land acquisition and site improvements like parking, gardens, and play areas or any demolition work. Materials would cost around $273,000, labor would cost roughly $268,700, machine costs would stand at roughly $9,800, and the contractor would take in over $79,100 for the project.

Cost breakout

What is included:

The basic design of the building would be rectangular in shape and in an uncomplicated "four square" design. Most developers automatically turn to both an architect and a contractor, and the architect will require an additional fee totaling roughly 10 - 17% of the total building budget;

  • An architect will:
    • Determine the scope of the project and establish a preliminary budget;
    • Draft list of proposed work, budget, and outline of plans;
    • Create the schematic design and draft floor plans with elevation drawings. Then work with any structural engineers and meet with planning agencies to verify any requirements;
    • Finalize drawings and incorporate all details about materials and finishes, any fixtures or equipment, and all systems in the structure;
    • Serve as the project manager and review the plans with any required local agencies while also obtaining necessary permits. (If contractors are to be used it is at this point that they must be selected);
    • Serve in an advisory capacity to select contractor and help the client through the bid review process as well;
    • Complete construction documents;
    • Administer the construction, ensure that contractor's requests for payments are accurate and that all "final" details are corrected or finished by the contractor; and
    • Based on figures given the architect on this project would receive from $55,100 to $93,800 for their services.
  • A contractor will:
    • Provide the services and materials required for the entire job;
    • Hire subcontractors according to need;
    • Suggest plans and ideas to developer to help them meet goals;
    • Deliver final cleanup of entire home;
    • Pull all permits for work and utility installation; and
    • For doing all of the day to day management of the project the average contractor earns around $85 per square foot. They might also "mark up" supplies and services as well. For example, on the average duplex construction described here the contractor could account for roughly $79,100 in markup and indirect fees.