How to Build an ADU (Accessory Dwelling Unit)

Ever wondered how to Build an ADU? We give you the exact steps that it takes to build an Additional Dwelling Unit! Building an Accessory Dwelling Unit is a fantastic way to create additional living space on your property. Whether you plan to use it as a guest house, rental unit, or private space for family members, constructing an ADU can be rewarding. In this blog post, we will guide you through the step-by-step process of building an ADU. Let’s get started!

So let’s get you started knowing the proper steps on how to build an ADU. These steps are a licensed contractor’s step-by-step guide. The list can get bigger depending on any minor changes or details you wish your ADU to have. So let’s start and read the step-by-step on ‘How to Build an ADU!’ to get your questions answered and get rid of any misinformation you might have.

1. Demolition & Surface Excavation for the ADU:

            Begin by clearing the area where the ADU will be constructed.

            Remove any existing structures or obstacles that may be in the way.

            Excavate the ground to create a level surface for the foundation.

How to Build an ADU
BEFORE2

2. Footing for ADU Foundation:

            Mark the layout of the ADU’s foundation on the excavated surface.

            Dig trenches for footings, ensuring they are deep and wide enough to support the structure (according to plans and city requirements).

            Install reinforcement bars (rebar) within the footings for added strength.

how to build and ADU
how to build and ADU

3. Inspection for Footing Foundation:

            Plan an inspection with the local building department to verify the footing meets the required standards.

4. Underground Plumbing:

            Putting in the necessary plumbing pipes and drains beneath the foundation.

            Connect them to the main sewer or septic system.

            Ensure proper slope and alignment for effective drainage.

How to Build an ADU

5. Inspection for Underground Plumbing:

            Call for an inspection to ensure the underground plumbing is correctly installed and meets code requirements.

6. Pouring Concrete Cement Slab Foundation/Raise Foundation Footings:

            Pour concrete into the trenches to create the foundation slab or raise the foundation footings.

            Level the concrete and allow it to cure according to the manufacturer’s instructions.

How to Build an ADU
CEMENT2

7. Framing:

            Construct the framing of the ADU using the lumber and appropriate structural elements.

            Follow architectural plans and local building codes for accurate framing assembly.

            Adding floor joists, exterior walls, interior partitions, and the roof structure.

How to Build an ADU

8. Rough Plumbing:

            Placing the plumbing pipes, fixtures, and fittings within the framed walls.

            Hook up the plumbing system to the existing water supply lines.

            Ensure proper venting and water flow throughout the ADU.

9. Rough Electrical:

            Adding electrical wiring, outlets, switches, and light fixtures as per the electrical plan.

            Connect the electrical system to the main power source.

            Consider hiring a licensed electrician for this step to ensure safety and compliance.

rough electrical installation

10. AC System Installation:

            Adding the heating, ventilation, and air conditioning (HVAC) system.

            Choose an appropriate system based on the ADU’s size and local climate.

            Follow the manufacturer’s instructions for installation and consider professional assistance if needed.

HVAC installation on how to build an ADU
HVAC installtion

11. Inspection for Rough Plumbing, Electrical, Mechanical:

            Schedule inspections to verify that the rough plumbing, electrical, and mechanical systems comply with local regulations.

12. Insulation:

            Placing insulation materials within the walls, ceilings, and floors.

            Use insulation appropriate for your climate to ensure energy efficiency and comfort.

How to Build an ADU
insulation

13. Exterior & Interior Lath:

            Add lath (a mesh or metal framework) on the exterior and interior walls.

            This provides a solid base for the next steps of construction.

lath installation
exterior and interior lath installation for how to build an ADU

14. Inspection for Interior Lath, Exterior Lath & Insulation:

            Request inspections to confirm that the lath, insulation, and exterior finish meet the required standards.

15. Drywall:

            Fit drywall sheets on the walls and ceilings.

            Cut and fit the drywall pieces carefully, leaving spaces for doors, windows, and electrical outlets.

• Install drywall sheets on the walls and ceilings. • Cut and fit the drywall pieces carefully, leaving spaces for doors, windows, and electrical outlets.
• Install drywall sheets on the walls and ceilings. • Cut and fit the drywall pieces carefully, leaving spaces for doors, windows, and electrical outlets.

16. Inspection for Drywall Screws:

            Timetable an inspection to ensure that the drywall screws are properly installed and meet the necessary specifications.

17. Drywall Taping (Walls and Ceiling Paint Preparations):

            Place joint compound to cover the joints between drywall panels.

            Smooth out the compound and allow it to dry.

            Sand the surface to achieve a smooth finish ready for painting.

drywalltaping

18. Interior Walls Painting:

            Select the desired paint colors and apply them to the walls and ceilings.

            Use brushes or rollers to ensure an even and professional-looking finish.

19. Stucco:

            Add stucco or other exterior finishes to the outside walls.

            Follow the manufacturer’s instructions for proper application and curing.

• Apply stucco or other exterior finishes to the outside walls. • Follow the manufacturer's instructions for proper application and curing.
• Apply stucco or other exterior finishes to the outside walls. • Follow the manufacturer's instructions for proper application and curing.

20. Cabinets & Countertops Installation:

            Establish kitchen cabinets, bathroom vanities, and other necessary cabinetry.

            Attach countertops to complete the installation.

cabinet countertop installation for how to build an ADU
cabinet countertop installation for how to build an ADU

21. Flooring:

            Choose and install the flooring material according to your preferences and budget.

            Common options include hardwood, laminate, carpet, or tile.

• Choose and install the flooring material according to your preferences and budget. • Common options include hardwood, laminate, carpet, or tile.

22. Tile Installment:

            If desired, install tiles in the bathroom, kitchen, or other designated areas.

            Certify proper alignment, grouting, and sealing for durability and aesthetics.

tile installation how to build an ADU
tile installation how to build an ADU

23. Adding of Interior Doors:

            Hang interior doors using appropriate hinges, handles, and hardware.

            Ensure they swing properly and fit within the door frames.

24. Fastening Plumbing & Electrical Finishes:

            Situating plumbing fixtures such as sinks, toilets, showers, and faucets.

            Fasten and test the electrical outlets, switches, and light fixtures.

25. Final Inspection:

            Organize a final inspection to ensure all aspects of the ADU construction meet the necessary standards and regulations.

            Address any concerns or issues raised by the inspector before proceeding.

Congratulations! You have successfully completed the construction and know how to build an ADU. Now you can enjoy the benefits of this additional living space. Remember to consult with local authorities, professionals, and experts throughout the process to ensure compliance with building codes and regulations. Happy building!

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