How Much Does a Home Addition Cost in San Diego in 2025?
If you're thinking about adding more space to your home, you're not alone. In North County San Diego, especially in coastal cities like Encinitas, Del Mar, Solana Beach, and Carlsbad, home additions are a popular way to increase livable space without giving up your location. But how much does it really cost in 2025?
Common Types of Home Additions
Not all additions are created equal. Here are a few common types we see in North County San Diego:
Room Additions: Adding a bedroom, bathroom, or guest suite is one of the most popular choices. These can be built out (on the ground floor) or up (as part of a second story).
Second-Story Additions: Ideal for homeowners who don’t want to lose yard space, second-story additions can include new bedrooms, bathrooms, home offices, or even full guest apartments.
Garage Conversions or ADUs: Converting an existing garage or building a detached Accessory Dwelling Unit (ADU) offers rental income potential or space for multigenerational living.
Multi-Room Additions: These involve adding several spaces at once, like a new wing with a bedroom, bathroom, and den, and are typically more complex in both design and permitting.
Second Story Addition in Encinitas, CA
Average Home Addition Costs in North County San Diego
How much does a home addition cost in San Diego in 2025? Costs can vary depending on the type and size of the project, but here’s a general breakdown to help you budget:
Small bump-out (100-200 SF): $50,000 - $90,000
Mid-size addition (bedroom + bath): $120,000 - $200,000
Large addition (500+ SF): $200,000+
Second-story addition: $250,000 - $400,000
Keep in mind: coastal homes, hillside lots, or tight urban lots often come with additional structural requirements and longer permit processes, which can drive up the total cost. This might affect places like Del Mar, Solana Beach, Encinitas and Carlsbad.
Factors that Influence the Cost of an Addition
Site Conditions: Sloped lots, poor access, or outdated utility lines can increase cost.
Permit & Zoning Requirements: Coastal cities like Del Mar and Encinitas may require California Coastal Commission approval, and that adds time and fees.
Size and Layout: Bigger isn’t always more expensive per square foot, but complex designs (multiple rooms, structural changes) will drive up cost.
Quality of Materials & Finishes: From foundation to finishes, your material selections matter. Luxury-level finishes, hardwood flooring, and custom cabinetry will impact budget.
Design Fees: Architectural planning, engineering, and city coordination are critical, especially in tight neighborhoods or coastal zones.
Does a Home Addition Require a Permit?
In short: yes, absolutely.
Any structural addition — even a bump-out or second story — will require permits. In cities like Encinitas and Del Mar, you may also need:
Design Review or Planning Department approval
Coastal Commission sign-off (if within the coastal overlay zone)
Stormwater management plans for larger additions
Navigating this process can be overwhelming, which is why we always handle permitting as part of our full-service design-build process.
How Long Does it Take to Build a Home Addition?
From design to move-in, here’s what to expect:
Design + Permitting: 3-6+ months (longer in coastal areas)
Construction: 3-6 months depending on the scope
We always recommend planning 6-12 months in advance, especially if you’re trying to align with summer or holiday timelines.
Need Help Planning a Home Addition?
We’ve helped homeowners throughout North County San Diego design and build additions that blend beautifully with their existing home and meet all local zoning and permit requirements.
If you’re considering a home addition in 2025, reach out for a consultation. We’ll walk you through the process, timeline, and what’s possible for your specific property.