The terms primary house and main house both refer to the principal residential building on a property.
The primary house (or main house) is the main dwelling unit that sits on a residential lot.
It’s the structure that zoning laws recognize as the primary residence.
Everything else on the lot — such as a detached ADU, garage, shed, or junior ADU — is considered secondary or accessory.
An accessory dwelling unit (ADU) is a secondary living space that shares the building lot of a primary home.
These livable spaces have a kitchen and bathroom, and are sometimes called granny fats, in-law units, or backyard homes. They offer a quick and low-impact way to add housing and increase the value of existing properties for California homeowners.
A building permit is an official approval from your city or county that allows you to begin construction, remodeling, or major repairs on your property. It ensures that your project complies with local building codes, zoning laws, and safety regulations.
Safety: Ensures construction meets structural, electrical, plumbing, and fire safety codes.
Legal Compliance: Without a permit, the city can issue fines, stop work orders, or even require demolition.
Property Value: Permitted work adds real value — unpermitted additions (like an ADU or remodel) may hurt resale value.
Financing & Insurance: Lenders and insurers typically require proof of permits for coverage and refinancing.
A setback is a zoning rule that defines how far a building (like an ADU, house, or garage) must be placed from the property lines (front, side, and rear).
R-1, R-2 and R-X zoning are types of residential zoning designations that tell you what kind of housing you’re allowed to build on a property. These labels come from city or county zoning codes, and while details vary by location, here’s the general meaning:
“R-1” = Residential, 1 unit per lot.
Typically allows only one primary dwelling (a single-family home).
Accessory Dwelling Units (ADUs) and Junior ADUs (JADUs) are usually allowed by state law, even if the local R-1 zone would normally restrict additional homes.
“R-2” = Residential, 2 units per lot.
Allows a duplex (two primary homes) on a single parcel.
With California’s ADU laws, you might be able to have:
2 main units (duplex)
1–2 ADUs (depending on lot size and city rules)
An easement is a legal right for someone else to use part of your property for a specific purpose — even though you still own the land.
Easements are recorded on the property deed and “run with the land”.
Utility Easement
For water, sewer, gas, electric, or cable lines.
Access Easement
Allows someone to cross your property to get to theirs.
Common in flag lots or shared driveways.
Drainage Easement
Keeps part of your land clear so stormwater can flow.
Public Easement
Sidewalks or pathways the public is allowed to use.
You generally cannot build an ADU (or any permanent structure) within an easement area.
Cities often require you to map all easements to confirm your buildable area.
If you build over one, the city could deny your permit or the utility company could legally tear it down to access their lines.
A duplex is a type of residential building that contains two separate housing units within one structure. Each unit has its own entrance, kitchen, bathroom, and living space, making it function like two independent homes — but on a single lot.
Two units in one building (side-by-side or stacked one above the other).
Each unit is typically around the same size, though layouts can differ.
Can be owned by one person (who rents one or both units) or sometimes split into condos.
Shares some systems or walls (like roof, plumbing lines, or foundation).