Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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AfterFast, Reliable Home Additions & ADU Across San Diego
A detached ADU or room addition in San Diego typically runs $53,100-$153,400, with ADU construction specifically ranging from $106,200-$259,600 depending on whether you’re building on a city lot in Clairemont or on acreage in Ramona. We’re Rowan Construction Group, and our Home Additions & ADU team has delivered 4,000-plus projects since 2007, every one with a written price before work started. Dispatch and scheduling run from our San Diego office, and crews serve the full metro including Coronado, National City, Chula Vista, and Lemon Grove. Call (858) 434-8926 to schedule your free estimate.
Why Rowan Construction Group San Diego Is San Diego’s Preferred Home Additions & ADU Company
San Diego homeowners research contractors the way they research appliances - they read the three-star reviews and want the price range before they make contact. We’ve built our reputation on giving it to them. Every quote is a flat written price with a written scope and a written warranty; “call for a quote” is not an option here.
Our crews are background-checked and uniformed, and a live person answers calls 24/7. Every visit includes a documented photo record as standard - not an upgrade - so you leave with evidence of what was found and what was done. The 365-Day Done Right Promise is printed on every page and backed by a terms page, not an asterisk. Under Clause 1 of the Haven Standard, the price is written before anyone starts.
We bring a free second opinion on any written estimate - bring a competitor’s quote and we’ll review it line by line at no charge. In San Diego’s mesa-and-canyon terrain, that second opinion often catches missing line items for engineered grading, retaining walls, or fire-hardening that out-of-area subs leave off bids.
Our Home Additions & ADU Services in San Diego
ADU Design & Permitting
ADU permitting in San Diego splits along a boundary most homeowners don’t discover until they’re deep into plans: city lots fall under San Diego Municipal Code, but unincorporated county pockets - Ramona, Lakeside, parts of Fallbrook and Jamul - route through San Diego County’s separate ADU ordinance. The county reviews against well and septic setbacks, not the city’s sewer connection rules. We scope which jurisdiction applies before we draw, because a set of plans stamped for the wrong authority is a six-week delay.
Garage Conversion ADU
Garage conversions in San Diego’s older neighborhoods - North Park, South Park, Mission Hills - often start with 1920s-1940s stucco-over-frame structures on clay soils that have heaved over decades. We assess the slab, the fire separation from the main dwelling, and the electrical service capacity before quoting. A garage conversion runs $35,400-$94,400, and the number moves if we need to upgrade a 100-amp panel or pour a new stem wall to meet current code.
New Detached ADU
New detached ADUs are where San Diego’s topography gets expensive. On a flat city lot in Carmel Valley, construction is straightforward. On acreage in Ramona or a hillside lot in Scripps Ranch, you’re looking at engineered grading, retaining walls, and WUI-compliant construction - ember-resistant vents, ignition-resistant cladding, Class A roofing - that contractors in flatter metros rarely encounter. We priced a 700-square-foot detached unit off Highland Valley Road where the septic percolation test and well-setback sign-off had to clear before the county would issue a building permit. Our tech ran 240 feet of underground conduit from the utility trench to the main panel while the lot was still open. The three words that prevented a mid-build dispute on the septic relocation were “in writing” - the allowance and the change order were both signed before we hauled a single yard of base material up the private drive.
Junior ADU & Interior Conversion
Junior ADUs work best in San Diego’s postwar tracts - Clairemont, Linda Vista, parts of Chula Vista - where the floor plan allows a separate entrance and the existing HVAC can handle a zoned extension. We verify ceiling height, egress window requirements, and whether the original 1960s electrical can support a kitchenette before we quote. The price stays flat because we found the problems during scoping, not during demo.
What happens when you call
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A real person answersNo phone trees - you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
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AfterTrusted Brands We Service in San Diego
We source across fifty-plus vetted brands, which lets us put honest numbers in the written quote rather than inflated allowances. For ADU and addition work in San Diego, we regularly specify James Hardie fiber-cement siding for WUI-compliant exteriors in fire-hazard zones, KraftMaid cabinetry for kitchenette builds, and Tuff Shed engineered structures where a shop or outbuilding precedes the main ADU. We don’t list brands to impress; we name them so the material line item in your quote matches a real SKU with a real delivery date.
Common Home Additions & ADU Problems We See in San Diego Homes
- Foundation heave on clay and decomposed-granite soils. Inland San Diego sits on expansive soils that shift seasonally. We see slab cracks and stem-wall separation in older Clairemont and Linda Vista tracts, and on open acreage in Ramona the percolation test sometimes forces a drainfield relocation that changes the ADU footprint.
- Fire-hardening requirements in WUI zones. Scripps Ranch, Rancho Bernardo, Santee, and El Cajon fall in High or Very High Fire Hazard Severity Zones. Chapter 7A of the California Building Code requires ember-resistant attic venting and ignition-resistant cladding - details that out-of-area subs miss on bids and local inspectors catch every time.
- Underestimated material haul and equipment access. A 40-foot private drive that isn’t load-rated for a loaded concrete truck turns a single pour into pump-truck and conveyor time. Nobody priced it. We verify access during scoping and write the contingency into the quote.
- County versus city permitting confusion. Because so much of San Diego’s buildable land sits in unincorporated county pockets, an ADU or shop there is permitted through San Diego County’s own ADU ordinance and reviewed against well and septic setbacks, not the city’s municipal code. Bidding off city permit assumptions is a common and expensive mistake.
Pricing for Home Additions & ADU in San Diego, CA
Here are the numbers for San Diego’s market. Every range is a flat written price with a written scope - not an estimate that shifts once work starts.
| Service | Price Range in San Diego |
|---|---|
| Home Addition | $53,100-$153,400 |
| ADU Construction | $106,200-$259,600 |
| Garage Conversion | $35,400-$94,400 |
What moves the number: county versus city permitting fees; well and septic setback work on unincorporated lots; engineered grading and retaining walls on hillside or canyon-adjacent sites; WUI fire-hardening materials in Scripps Ranch, El Cajon, and Ramona; and equipment access - pump trucks, conveyors, or crane time for long material hauls on acreage. We scope all of it before we quote. No change proceeds without a signed change order, which is the discipline that has kept our projects within a few percent of the agreed cost across 4,000-plus jobs. Call (858) 434-8926 for your free estimate.
We Also Serve Cities Near San Diego
Our crews work throughout the metro, including Home Additions & ADU in San Diego proper plus Coronado, National City, Chula Vista, and Lemon Grove. Permitting rules shift at municipal boundaries - Chula Vista has its own ADU ordinance, National City routes through county review for some parcels - and we verify jurisdiction before we draw.
Serving San Diego, CA - Our Local Coverage Area
We’re based in the San Diego area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs - Home Additions & ADU in San Diego
A detached ADU in Ramona or Lakeside pulls a San Diego County permit, not a city permit, because both communities sit in unincorporated county territory. The county reviews against well and septic setbacks, not municipal sewer connections, and requires percolation test sign-off before issuing a building permit. Call (858) 434-8926 and we’ll verify your parcel’s jurisdiction during the free estimate.
Three things move the number: well and septic setback work replaces sewer connection; equipment access often requires pump trucks or conveyors for concrete and framing materials; and engineered grading with retaining walls is more common on open slope lots. A city lot in Clairemont might need none of these; a hillside acre in Ramona might need all three. We scope each during site visit and write the contingency into the flat price.
Scripps Ranch and El Cajon sit in state-designated High or Very High Fire Hazard Severity Zones, so Chapter 7A WUI-compliant construction is baseline code, not optional. Ember-resistant vents, ignition-resistant cladding like James Hardie fiber-cement, and Class A roofing add material and labor cost that flat-metro contractors don’t encounter. Local inspectors catch missing fire-hardening every time, so we spec it from the first line item.
We don’t start until the county signs off on percolation test results and well-setback compliance. On a recent Ramona project off Highland Valley Road, we set a 4-inch PVC drainfield line and a 1,200-gallon tank before forming the slab, because the county won’t issue a building permit without both on file. The allowance and the change order were signed in writing before we moved base material. Call (858) 434-8926 to schedule your free estimate.
Payment is milestone-based, tied to signed change orders and documented photo records at each phase: foundation, framing, rough mechanical, finish, and final. Under the Haven Standard, no work proceeds on a change until the change order is signed, so the schedule you see at signing is the schedule you pay. The 365-Day Done Right Promise covers the completed work. Call (858) 434-8926 for exact terms on your project.
Written by Grant Rowan, Owner at Rowan Construction Group, serving San Diego since 2007.