How Much Does It Cost to Build a 4–6 Unit Building in San Diego?

If you're considering building four to six residential units in San Diego County, one of your first questions is probably: “How much is this going to cost?”

For preliminary 2026 planning, San Diego multifamily construction benchmarks put garden-style wood-frame hard construction costs at approximately $175,000–$265,000 per unit. That suggests roughly $700,000–$1.06 million for four units and $1.05–$1.59 million for six units in hard construction costs alone. Those figures are market benchmarks not an RCS Pro Build quote.

The actual cost can be considerably different depending on unit size, number of stories, parking, site conditions, utilities, fire and life-safety requirements, finishes, structural design, and the property itself. For a project like this, the most important question isn't simply:

“What does six units cost?”

It's:

“What can we build on this specific property, and what will that design require?”

What Does a 4–6 Unit Project Look Like?

Suppose you're planning two bedroom units averaging approximately 850–1,000 square feet each.

That could mean:

Approximate Unit Area*

2026 Hard-Cost Benchmark

4 units

3,400–4,000 sq. ft.

$700K–$1.06M

5 units

4,250–5,000 sq. ft.

$875K–$1.33M

6 units

5,100–6,000 sq. ft.

$1.05M–$1.59M

*Unit area only; the completed building may require additional square footage for stairs, circulation, utility spaces, walls, and other building components.

These estimates use current San Diego garden-style multifamily per-unit benchmarks. More complex podium, concrete, or steel construction can cost substantially more.

Hard Costs vs. Total Development Cost

This distinction is extremely important.

Hard construction costs: Hard costs generally include the physical work required to construct the building:

Site work
Foundation
Framing
Roofing
Windows and doors
Plumbing
Electrical
HVAC
Insulation and drywall
Kitchens and bathrooms
Flooring
Interior finishes
Exterior finishes

Soft and development costs: The overall project may also include:

Architectural design
Structural and civil engineering
Surveying
Soils/geotechnical work
Planning and entitlement
Building permits
Development and impact fees
Utility fees and upgrades
Financing and carrying costs
Insurance
Legal or consulting costs
Contingency

Current San Diego multifamily benchmarks suggest soft costs can add approximately 20%–30% above hard costs, depending on the project.

Land acquisition would generally be considered separately. That's why a "$1 million construction project" should not automatically be interpreted as a "$1 million total development."

What Determines the Cost?

1. Number and Size of Units

Four 750-square-foot units are a very different project from six 1,100-square-foot units. Before discussing a serious construction budget, establish:

Number of units
Bedrooms per unit
Bathrooms per unit
Approximate square footage
Desired finish level

More units also mean more kitchens, bathrooms, electrical systems, HVAC equipment, appliances, and plumbing fixtures.

2. Number of Stories

How the units are arranged can have a major effect on cost. A compact two-story building may use the property differently from a larger single-story configuration.

Additional stories can also introduce stairs and more complex structural and life-safety considerations. The least expensive layout isn't always the one with the fewest stories. The property needs to be evaluated as a complete development.

3. Parking

Parking can have a major impact on site planning. Before designing the building, determine how vehicles, pedestrian access, trash areas, landscaping, and the building itself can work together on the lot. A design that looks great on paper isn't useful if it doesn't work with the property's development requirements.

4. Site Work and Utilities

The building is only part of the construction project. The site may require:

Demolition
Clearing
Grading
Excavation
Retaining walls
Drainage
Sewer work
Water service
Electrical service
Utility trenching
Driveways and paving

A relatively flat property with good access and nearby utilities can have a very different budget from a difficult hillside site.

5. Kitchens and Bathrooms

Every additional unit requires its own major interior systems. For six two-bedroom units, you're potentially building: 6 kitchens + 6 or more bathrooms.

Cabinetry, countertops, appliances, plumbing fixtures, tile, electrical, ventilation, and labor add up quickly. One way to control costs is to standardize finishes and layouts across the units where practical.

Why La Mesa Property Feasibility Comes First

For someone considering a four-to-six-unit project in La Mesa, RCS Pro Build would want to evaluate the property before developing a meaningful construction estimate.

La Mesa's zoning regulations govern factors including permitted uses, density, lot dimensions, structure height, parking, and other development standards. The city's published fee schedule also specifically identifies 4–10 residential units as a category for Site Plan Review, demonstrating why a small multifamily project should be approached differently from a typical single-family remodel. Before spending heavily on design, investigate:

Zoning and density

How many units can the property support?

Building envelope

Where can the structure actually sit on the lot?

Height and setbacks

How do these affect the number of stories and available building area?

Parking and circulation

How will vehicles and people enter and move through the property?

Utilities

Can the existing infrastructure support the proposed development, or will upgrades be necessary?

This is why having enough physical space for six units doesn't necessarily mean six units can be built as imagined.

How Can You Control Multifamily Construction Costs?
Keep Unit Layouts Consistent

Repeating floor plans can simplify framing, plumbing, electrical, cabinetry, and material purchasing.

Stack Plumbing Where Possible

Thoughtful placement of kitchens and bathrooms can reduce unnecessary plumbing complexity.

Design With the Budget From the Beginning

Don't complete an elaborate architectural design and only afterward discover what it costs to build. The owner, designer, engineers, and contractor should understand the target budget early.

Choose Durable, Repeatable Finishes

For rental units, durable materials often make more sense than highly customized finishes. Standardizing cabinets, flooring, fixtures, appliances, and paint can also simplify purchasing and future maintenance.

Don't Underestimate the Site

A project's site work and infrastructure can significantly affect the budget. Evaluate these conditions early rather than treating them as an afterthought.

Helpful Questions to Ask Before Building 4–6 Units

Before requesting a construction estimate, be prepared to answer:

Do you already own the property?
What is the property address?
What is the lot size and zoning?
Are you targeting four, five, or six units?
How large should each unit be?
How many bedrooms and bathrooms?
How many stories are you considering?
Is there an existing structure to demolish?
Do you already have architectural plans?
What is your overall development budget?

The property address is especially important because it allows the project team to begin evaluating what may actually be feasible.

Frequently Asked Questions

How much does it cost to build a fourplex in San Diego?

For early 2026 planning, a San Diego garden-style wood-frame multifamily benchmark of approximately $175,000–$265,000 per unit suggests around $700,000–$1.06 million in hard costs for four units. Actual costs depend on the property and project.

How much does a six-unit apartment building cost?

Using the same benchmark, six units could represent approximately $1.05–$1.59 million in hard construction costs before soft costs, land, and other development expenses.

Are architectural plans included in construction cost?

Not necessarily. Architecture, engineering, planning, entitlement, permits, financing, and other professional expenses are often considered soft costs and should be clearly identified when comparing budgets.

Is building six units cheaper per unit than four?

It can create economies of scale because certain costs are shared across more units, but it isn't guaranteed. A six-unit project may require a larger or more complex building, additional site work, or different construction solutions.

Can I build six units on my La Mesa property?

Possibly, but the answer depends on the specific property, zoning, density, lot dimensions, development standards, and proposed design. A feasibility review should happen before assuming a particular unit count.

What should I do before getting a construction estimate?

Start with the property address, desired unit count, approximate unit size, number of stories, and overall budget. If plans already exist, they can provide much more information for developing a meaningful estimate.

Planning a 4–6 Unit Project in San Diego?

A four-to-six-unit building can be a substantial investment, and the most expensive mistakes often happen before construction begins. The right first step isn't choosing countertops or asking for a single price per square foot. It's determining what the property can support, what you want to build, and how those decisions affect the construction budget. For a La Mesa property, that means evaluating the site, development requirements, unit count, parking, utilities, building configuration, and desired finishes before committing to a final number.

RCS Pro Build can help property owners and investors evaluate the construction side of a small multifamily project and develop a clearer picture of what it will take to move from an idea to a buildable project.

Considering a 4–6 unit project in La Mesa or the greater San Diego area? Contact RCS Pro Build to discuss your property, project goals, and next steps.

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