8 Key Sample ADU Building Inspections
Since accessory dwelling units are generally smaller units (although they can be as large as up to 1,200 square feet in some jurisdictions), some homeowners embarking on an ADU build are caught off guard by the fact that ADU builds require multiple building inspections. After all, even if your ADU is small, it still contains all the same structural and other elements of a full habitable home -- utilities, plumbing, foundation -- you name it!
All building inspections will be conducted by your local building official. The purpose of building inspections is to ensure that the construction work meets the requirements of the building code.
Generally speaking, when the building inspector comes to your property to conduct an inspection they will not look into other projects or parts of your property -- they are there solely for the purpose of the inspection they were invited to conduct.
Keep in mind that the list below pertains only to ADUs that are “stick built,” aka traditional construction. If your ADU is a fully-constructed prefab unit then the unit itself (such as shear and sheathing, for example) has already been inspected and approved by a third-party inspector approved by the State of California or the United States Department of Housing and Urban Development. This means that when it comes to inspections by your local city or county, for a prefab unit the inspections will be limited to new construction elements required on-site such as the foundation and utilities improvements needed for your project.
Here is a list of 8 sample key inspections that will likely be required for your traditionally constructed ADU project, just like in a regular home build project. Note that the inspections required will differ depending on your jurisdiction and your ADU project.
Underground Utilities: This includes inspection of sewer, water, gas, and electric.
Foundation: This includes size, reinforcement, hold down bolts and anchors.
Under Floor/In-Wall: This includes plumbing, electrical, mechanical and insulation.
Shear and Sheathing: This is a structural inspection that includes checking the plywood type, nailing, connection of clips, straps, and hold downs at the interior and exterior walls, the floors and roof.
Close-in: This includes framing, electrical, plumbing, mechanical, and fire sprinklers. At this inspection, the inspector also gets a final look at the placement of the structural hardware such as straps, hold downs, hangers, clips and brackets.
Insulation of Walls and Ceilings: The purpose of this inspection is to verify proper placement, materials of sufficient R-value have been used, and air barrier has been properly installed. (Note: R-value is the capacity of an insulating material to resist heat flow. The higher the R-value, the greater the insulating power.)
Wallboard fasteners and shower pans: This inspection ensures that the sheetrock and shower pan have been installed correctly.
Building Final: This is the final inspection -- after this, depending on the jurisdiction, you’ll get a “certificate of occupancy” or otherwise be fully signed off on the ADU build -- it is now ready for move-in!
Inspections are done over time throughout the course of the entire build process.
Unless you’re running the ADU project as a project manager or Owner Builder, your general contractor or builder should be in charge of knowing when an inspection needs to be scheduled, scheduling it with the local building department, and being present during the inspection.
Keep in mind that the rule of thumb throughout the build process when it comes to inspections is, don’t cover anything until your local building inspector has seen it. If in doubt, call or send an email to your building inspector to ask if you should schedule an inspection.
Check out these handy related resources from Napa Sonoma ADU:
Our ADU Workbook starting at page 77.
Our Vendor Registry where you can find builders and general contractors for your project
Our library of on-demand ADU webinars where you can hear from local building officials in many Napa and Sonoma County jurisdictions about the local building requirements and inspections
And sign up for an ADU Feasibility Consult with us to get more insights into what your specific ADU project will likely entail!