Though an ADU is a smaller version of a home they still require the same amount of permitting and construction to get completed. ADUs do face some unique challenges during their construction process. They are generally located in the rear of the homes lot which can make them difficult to access and there is less room for large equipment to operate and expedite the construction. Some ADUs are built on previously existing structures which may require complete demolition or heavy modification to support the construction of an ADU. All projects are different but we outline the basic elements of the process you can expect to complete the construction of an ADU.
Before taking any significant steps towards the construction of an ADU make sure that you confirm that your home is zoned for one! ADU design and permitting is not the same as standard home construction and thus professionals with relevant experience are worth their costs. Using an inexperienced professional could cost you much more in the long run via delays, holding costs, or having to hire the appropriate professional after the failure of your primary hire. In the initial sequencing of steps its important to make sure all of the correct paperwork is approved and filed to mitigate construction delays.
- Is your property zoned?
- Are you using an existing structure or building new?
- Identify appropriate architect for your project
- Convert ideas into conceptual drawings
- Architectural drawings
- Mechanical, electrical, and plumbing schematics added to plans
- Get approval from landmark or historical commission
- Submit completed plans to city zoning and permitting departments
- If you have a variance it needs to be denied before moving to the Board Of Adjustments
- Construction permits supplied
After permits have been granted the construction team will start on the foundation and exterior of the house. Through the first 6-8 weeks of construction, the shell of the home will start to take place. Units being built on existing foundations may require additional time to get them updated and prepared. Exterior construction is completed as follows:
- Break ground
- Pour foundation
- Rough in utilities
- Dry in
If all is going to plan, the exterior construction of an ADU should be completed between the 2-3 month mark. At this point, the contractors are able to start making the ADU yours by installing the finishes you've selected. The main internal elements of the unit will be installed first followed by the final fit and finish pieces to keep areas open and to mitigate any potential damage.
- Rough plumbing
- Mechanical work
- Air sealing
- Dry wall
- Plumbing and electrical fixtures
After everything has been installed the city inspector will come out to the property to verify the construction is up to code. Once they have inspected and authorized the new construction they will issue you a Certificate Of Occupancy. This will allow you to legally live in or rent the ADU out.
The final costs of an ADU will vary greatly from project to project. The real difference in prices comes from the drywall out. Many homeowners find themselves having to reselect fixtures in order to stay on track with their budget. If you know what you want to do with your ADU you should select your finishes accordingly. A long term rental should have durable fixtures and there should be less concern about the luxury nature of them. A unit that is going to be lived in by the owners will likely have more luxurious finishes to satisfy their personal needs.
In Denver, we estimate that an ADU will cost about$230,000 minimum to build. Due to the high demand for construction professionals, building for below that price is nearly impossible. Anyone wishing to build an ADU on their property should expect the process to take at least 1 year once you have formally started working with an architect. The design and permit side of the process generally take between 4-6 months and the construction part of the process 6-8 months. An active homeowner can resolve problems and make changes to the plans to help keep the project on track and delays to a minimum.