Like with previous steps, unless you have extensive construction experience, it is ill-advised to build an ADU by yourself.

If you have spare time, are detail-oriented, and are good at finding the needed subcontractors (sitework, concrete, framing, roofing, siding, electrical, plumbing, insulation, drywall, painting, finish carpentry, and landscapers) you may decide to try to oversee construction in the role of general contractor (GC) yourself. A GC hires and coordinates specialized subcontractors for all the phases of construction and permit inspection so that each show up in the right order at the right time.

Otherwise, you will need to hire a general contractor to oversee your project. General contractors, especially good GCs, will have their schedules filled up months or even years in advance. Keep it in mind that once you hire a GC, they may not be able to start work on your property for quite some time. In this down time, make sure you have your permitting in order, as permitting often requires long waiting periods (see PERMITTING).

Bear in mind that changes in material costs may dramatically change your project’s original financial picture, and, if your project is in Vermont, be sure to account for Vermont’s Commercial and Residential Building Energy Standards. Watch this Zoning Administrator Training put on by TRORC for more information on that topic.

Also, have a timeline in mind for construction. Construction projects like this often run longer than estimated and can have significant delays caused by inclement weather, especially in snowy Vermont and New Hampshire. Interior work can happen in the winter, but sitework and rough framing are best when it is not freezing. Options that minimize construction delays include using a pre-fabricated ADU unit that is built off site and placed on the foundation with a crane. ‘Panelized’ or modular homes are prebuilt in parts and assembled with a crane on site. Many companies are now offering different levels of finish for those willing to do some of the last stages themselves. Wheelpad and Backyard ADUs have many pre-fabricated homes, and  Preferred Building Systems is a local supplier of modular construction.

Lastly, discuss with your contractor whether it will be necessary for you to move off-site for any length of time during the project due to any number of reasons, including connecting the ADU to your wastewater system or electrical system.

Once your unit is finished, it’s time to move on to the RENTING or SELLING phase.