Mixed-Use Buildings: Buying, Financing and Zoning in the North Bay
A mixed-use property is a building that combines commercial space, such as a storefront, office or restaurant, with one or more homes or apartments, usually upstairs or behind the ground floor. In North Bay downtowns that typically means a shop on the street with apartments above. How much of the building is commercial decides how you can finance it, and the zoning, accessibility and tenant laws that apply come from both sides of the building.
Mixed-use buildings appeal to two kinds of buyer: owner-users who want to run a business downstairs and live or rent out the space upstairs, and investors who want two income streams in one property. This guide covers financing options by building type, zoning in downtown districts, accessibility, rent rules for the apartments, shared utilities and the due diligence that’s specific to this property type. It sits under our commercial real estate services.
Which loan fits which mixed-use building?
Lenders sort mixed-use property by how residential it is. The more commercial the building, the more likely you’ll need a commercial loan instead of a home loan.
| Building | Financing usually available | Key condition |
|---|---|---|
| A home with a small business space the owner runs | Conventional (Fannie Mae) loan | One-unit dwelling, owner-occupied, owner operates the business, primarily residential |
| One to four homes with a storefront, owner living there | Possibly FHA | Non-residential share within FHA limits; legally permitted; residential character preserved |
| Owner-user business with apartments or other tenants | Commercial bank loan, or SBA 7(a) or 504 | For SBA, the business occupies at least 51% of an existing building |
| Investor-owned storefront with apartments | Commercial or portfolio loan | Underwritten on the building’s income |
Conventional loans: one unit, owner-operated
Fannie Mae’s Selling Guide (topic B2-3-04, dated October 8, 2025) allows a mixed-use property only if it’s a one-unit dwelling the borrower occupies as a principal residence, the borrower both owns and operates the business, and the property is “primarily residential in nature.” The appraisal rules (B4-1.4-07) require the appraiser to confirm the mixed use is legal under local zoning and to value the property on its residential characteristics, not the business use. A storefront building with apartments upstairs usually doesn’t fit.
FHA: one to four units
FHA’s Single Family Housing Policy Handbook 4000.1 has a section on mixed-use one- to four-unit properties (section II.D.12 in the August 2026 update). We could not retrieve that section’s text from HUD’s site, so the figure that follows comes from a lender-compliance summary of the handbook by LoanLogics: there, for FHA case numbers assigned since September 14, 2015, the non-residential part can be up to 49% of the total floor area, provided the use is legally permitted, meets current zoning and doesn’t impair the property’s residential character or marketability. FHA financing is aimed at buyers who will live in the property, so it suits someone moving into one of the units. Treat the 49% figure as a starting point and have an FHA lender confirm the current handbook rule and its occupancy requirements before you write an offer. Our guide to financing 2–4 unit properties covers the residential side of that choice.
SBA and commercial loans for owner-users
If your business will occupy the building, SBA financing may work. SBA rules at 13 CFR 120.131 require the business to occupy at least 51% of the rentable space in an existing building and allow it to lease out up to 49%; for new construction it’s at least 60% occupied, with up to 20% leased out. Our comparison of SBA 504 and 7(a) loans and our guide to buying an owner-user commercial property explain the trade-offs. Investor buyers typically use commercial or portfolio loans sized on the building’s income.
Diamond may refer you to partners we work with, such as lenders; you’re free to choose any provider.
Zoning: is the mix allowed?
Downtown zoning in most North Bay cities allows housing above or behind ground-floor commercial space, but the details vary by district, and some blocks require a shop or other active use on the street. The table compares five downtowns; the notes below give the code references.
| Downtown | Zoning tool | Housing in a mixed-use building | Ground floor | Extra review |
|---|---|---|---|---|
| Santa Rosa | Core Mixed Use (CMU) and other mixed-use districts, Downtown Station Area Specific Plan | Permitted in CMU, SMU, MMU and NMU | Activity-generating uses required along public streets in the Courthouse Square sub-area | Landmark Alteration Permit for landmarks and preservation districts |
| Napa | Downtown Specific Plan districts (DCC, DMU, DN) | Multifamily permitted on upper levels in DCC; on both levels in DMU and DN | No multifamily on the DCC ground level | Design review for new mixed-use buildings, additions and exterior remodels |
| San Rafael | Downtown Precise Plan form-based code | Set by the code’s zones; confirm by parcel | Set by building form and frontage standards | Code protects historic resources; check the plan’s historic survey |
| Petaluma | SmartCode (form-based, 2003) | Permitted in T4, T5, T6, T6-O and D4 | Where a shopfront is required, housing only upstairs or behind | Ask about historic district review |
| Point Reyes Station | County C-VCR zoning, coastal zone | Commercial/residential district | Village commercial core | Design review; coastal permit for some work |
Santa Rosa
Santa Rosa’s zoning code (section 20-23.020) says the Core Mixed Use district is meant “to foster a mix of residential and nonresidential uses to activate the greater Old Courthouse Square area,” and Table 2-6 permits multifamily housing, the residential part of a mixed-use project and live/work units in the CMU, Station Mixed Use, Maker Mixed Use and Neighborhood Mixed Use districts without a use permit. On mapped sites in the Courthouse Square sub-area of the Downtown Station Area Specific Plan, projects must be mixed use and “provide activity-generating uses at the ground floor along all public streets,” and some office, bank and medical uses need a use permit on the ground floor.
Historic status adds a layer. Under section 20-58.060, exterior changes to a designated landmark, or to a building in a preservation district, need a Landmark Alteration Permit, decided by the Zoning Administrator for minor work and the Design Review and Preservation Board for major work. Repainting previously painted surfaces is exempt. Our Santa Rosa guide covers the rest of the city.
Napa
Downtown Napa is zoned under its Downtown Specific Plan into districts including Downtown Core Commercial (DCC), roughly First Street from School Street to the Napa River and Main Street from Fifth Street and the Napa Mill to Caymus Street; Downtown Mixed Use (DMU) around it; and Downtown Neighborhood (DN) on the edges. The city’s use table lists ground level and upper levels separately: multifamily housing is permitted on DCC upper levels but not on the DCC ground floor, and is permitted on both levels in DMU and DN. Under section 17.10.050, new mixed-use structures, additions and exterior remodels require design review.
San Rafael
San Rafael’s Downtown Precise Plan includes a downtown form-based code that, the city says, replaces many provisions of its Title 14 zoning code and regulates building form, size and design, with the design guidelines folded in as advisory guidance. Its consultant, Opticos Design, describes a 265-acre plan area and a code that protects historic resources and adjacent neighborhoods, and the plan’s appendices include an updated historic resources survey. Because the form-based code sets frontage and use rules by zone, ask the planning division which zone a building is in and whether it appears in the historic survey before you plan changes.
Petaluma and Point Reyes Station
- Petaluma. The city’s SmartCode, a form-based code adopted in 2003 for about 400 acres of central Petaluma, lists “residential in mixed use building” as permitted in its T4, T5, T6, T6-O and D4 zones. Where a shopfront is required on the frontage, residential use is allowed only on upper floors or behind an allowed ground-floor use. Live/work units are permitted in T4 and T5 and need a use permit in T6. See our Petaluma real estate guide for the rest of the city.
- Point Reyes Station. In unincorporated West Marin, downtown parcels can be zoned Coastal Village Commercial/Residential (C-VCR). County findings for one 2026 project show that modifying a structure in that district needs design review, and that a new septic system or substantial alteration of a pre-1930 building triggered a coastal development permit. Our Point Reyes Station guide explains the coastal rules.
For any building, check four things with the planning department: whether the current mix of uses is permitted or legally nonconforming; whether converting a ground-floor space to housing, or upstairs space to offices, is allowed; any historic district or design review that covers exterior changes; and parking requirements if you change a use. Ask for permit history too, since an apartment that was never permitted is a common problem in older downtown buildings.
Accessibility on the commercial floor
The storefront is a place of public accommodation, so accessibility law applies to it. Under California Civil Code section 1938, a lease of commercial property signed on or after January 1, 2017 must state whether the premises have been inspected by a Certified Access Specialist (CASp). If there’s no CASp certificate, the lease must include statutory language telling the tenant it can request an inspection, and the parties must agree on who pays for it and for any repairs. Unless the parties agree otherwise, correcting violations in a CASp report is presumed to be the owner’s responsibility.
When you buy, ask the seller for any CASp report, look at entrances, restrooms and paths of travel, and budget for work the report may require. Our guide to CASp inspections and ADA compliance covers the details.
Rent rules for the apartments
The apartments in a mixed-use building are still housing. California’s rent cap in Civil Code section 1947.12 applies to residential real property, and the statute doesn’t exempt a unit because it sits above a store. Its own exemptions still apply, including units with a certificate of occupancy issued in the previous 15 years. Covered units can’t be raised more than 5% plus the change in the cost of living, or 10%, whichever is lower, over 12 months. Local ordinances can be stricter, so check the city as well; our guide to AB 1482 for landlords explains coverage and notices.
The commercial space has no rent cap, and its lease terms decide much of the building’s value. Read whether the commercial tenant pays a share of taxes, insurance and maintenance, and when the lease expires. Our overview of commercial lease types explains the common structures, and tenant estoppel certificates let you confirm every lease before closing.
Shared utilities and common costs
Older mixed-use buildings often share one water meter, and sometimes one gas or electric service, between the shop and the apartments. That affects both the expenses and what you can bill back. California’s water submetering law covers submeters in “a multiunit residential or mixed-use structure,” and where a landlord bills water through submeters, the statute lets fixed charges be split by each tenant’s share of usage or equally among all residential and nonresidential units.
Before you buy, find out which meters serve which spaces, who pays each bill today and what the commercial lease says about utilities and common-area costs. If those terms are loose, the expense side of the building’s net operating income will be too.
Due diligence checklist for a mixed-use building
- Confirm the legal use. Zoning, permit history and certificates of occupancy for every unit and the commercial space.
- Collect all leases. Commercial and residential, with amendments, deposits and estoppels.
- Value each part. Residential and commercial income are often valued at different cap rates; ask how the appraiser or broker treated each.
- Check accessibility. CASp report, if any, and the lease disclosures under Civil Code section 1938.
- Map the utilities. Meters, sub-meters, shared systems and who pays.
- Inspect for older-building issues. Seismic condition, fire separation between the shop and apartments, and the condition of the roof, wiring and plumbing.
- Insure the whole building. Get a quote for a policy that covers both the commercial use and the apartments.
- Match the loan to the building. Confirm the lender will finance this mix before your loan contingency runs.
Our full commercial due diligence checklist adds title, environmental and survey items.
Selling a mixed-use building
A mixed-use building sells to whichever buyer pool its financing allows, so present it to the right one. A one-unit live/work property may reach owner-occupant buyers with conventional loans; a storefront with several apartments will sell mostly to investors and owner-users using commercial or SBA loans. Assemble the leases, a rent roll, operating statements, permits and any CASp report before listing. Our guide to selling commercial property covers marketing and pricing, and our Sonoma County commercial page covers that market.
Questions people ask
What is a mixed-use property?
A building that combines commercial space, such as a shop, office or restaurant, with residential units. In downtowns it’s typically a storefront with apartments above.
Can I get an FHA loan on a mixed-use property?
Possibly, for a one- to four-unit property you’ll live in. FHA’s handbook covers mixed-use properties in section II.D.12, and a lender-compliance summary of its rules says the non-residential part can be up to 49% of the floor area if the use is legal and the property keeps its residential character. Confirm the current rule with an FHA lender.
Does Fannie Mae finance mixed-use buildings?
Only narrowly. Fannie Mae’s guide allows a one-unit dwelling that the borrower occupies, where the borrower owns and operates the business and the property is primarily residential.
Can an SBA loan be used to buy a building with apartments?
SBA rules require your business to occupy at least 51% of the rentable space in an existing building, and the rest can be leased. Whether a particular building qualifies is a question for the SBA lender.
Does AB 1482 apply to apartments above a store?
The state rent cap applies to residential real property and doesn’t exempt units for being in a mixed-use building. Its usual exemptions, such as housing with a certificate of occupancy issued in the last 15 years, still apply.
Can I live above a store in downtown Napa or Santa Rosa?
Generally yes, subject to the parcel’s zoning. Santa Rosa permits housing in mixed-use projects in its downtown mixed-use districts, and Napa permits multifamily housing on upper levels in its Downtown Core Commercial district but not on the ground floor there. Confirm the specific parcel with the city.
Do I need a CASp inspection to buy a mixed-use building?
California doesn’t require one to buy, but commercial leases signed since January 1, 2017 must disclose whether the space was CASp-inspected, and the owner is presumed responsible for fixing violations a report identifies unless the lease says otherwise.
If you’re looking at a downtown building with a storefront and apartments, or thinking of selling one, we can help you sort out the financing path, the zoning and the leases before you commit. Contact us about a specific property.
This is general information, not legal or tax advice; talk to a California real estate attorney, lender or tax adviser about your situation.
Sources & notes
- Fannie Mae Selling Guide: B2-3-04, Special Property Eligibility Considerations (October 8, 2025)
- Fannie Mae Selling Guide: B4-1.4-07, Mixed-Use Property Appraisal Requirements (June 4, 2025)
- HUD: Housing handbooks and Single Family Housing Policy Handbook 4000.1, Update 18 (August 12, 2026), section II.D.12
- LoanLogics: Financing a mixed-use property under HUD Handbook 4000.1
- eCFR: 13 CFR 120.131, SBA occupancy requirements
- City of Santa Rosa Code: Chapter 20-23, Commercial Zoning Districts (section 20-23.020 and Table 2-6), via eCode360
- City of Santa Rosa Code: Chapter 20-58, Historic and Cultural Preservation (section 20-58.060), via eCode360
- City of Napa Municipal Code: Chapter 17.10, Commercial Districts (sections 17.10.010, 17.10.050 and Table B, Downtown Specific Plan Area), via eCode360
- City of San Rafael: Downtown Precise Plan and What’s in the plan?
- Opticos Design: San Rafael Downtown Precise Plan and Form-Based Code
- City of Petaluma: SmartCode Section 3, Building Function Standards and Congress for the New Urbanism: Petaluma SmartCode adoption (2003)
- County of Marin: Wilson Coastal Development Permit, Master Use Permit and Design Review (P5581)
- FindLaw: California Civil Code section 1938 (CASp disclosure)
- FindLaw: California Civil Code section 1947.12
- FindLaw: California Civil Code section 1954.202 and section 1954.205
The FHA floor-area figure comes from a lender-compliance summary because the text of handbook section II.D.12 could not be retrieved; confirm it against HUD Handbook 4000.1 with your lender. Zoning rules change and apply parcel by parcel; confirm them with the city or county planning department.
Last reviewed October 2026 by Matthew Martinez.
