Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
Before
After
Before
After
Before
AfterFast, Reliable Home Additions & ADU Across San Diego
Adding square footage to a San Diego home isn’t like building on a flat, open lot in El Cajon. In the canyon-rim neighborhoods that make up so much of central San Diego, every addition sits on ground with opinions: decomposed granite slopes, hillside review requirements, and neighbors close enough to hear a hammer drop. A typical home addition in San Diego runs $53,100 to $153,400, and a full ADU construction usually lands between $106,200 and $259,600. The number that matters most is the one that holds up once the city gets involved. Call (877) 610-1318 for a free estimate from a crew that works these lots every week.
Why Barrett & Sons Construction Is San Diego’s Preferred Home Additions & ADU Company
Tom Barrett founded Barrett & Sons Construction in 1998, and he still answers his own phone. The company’s Home Additions & ADU team is built around his sons running the crews, not dispatching strangers from a call center. Every price change arrives as a written change order before work begins, and every eligible job gets permits pulled and inspections signed. The permit inspector works for you, not for us, and that’s exactly why we like him on site.
San Diego homeowners tell us the same story over and over: a national company quoted one number, then handed them another at the door. We price differently. Allowances in writing, scope in writing, change orders in writing. The 90-Day Done Right Promise is printed on every contract: if it’s not done right, one call brings Tom back. Ask anyone on your street, or look up the license number yourself.
Our Home Additions & ADU Services in San Diego
ADU Design & Permitting
On a Mission Hills lot near a canyon edge, the design conversation starts with the City of San Diego Hillside Review. Most additions in 92103 and 92104 trigger a soils report and retaining wall engineering before a single stud gets touched. We handle that paperwork from day one, so the design doesn’t stall at the counter.
Garage Conversion ADU
Converting a detached 1920s garage into a permitted ADU in San Diego means checking what the original slab is actually sitting on. We regularly find decomposed granite fill with no drainage under these garages in North Park and South Park. We add engineered retaining walls, new subfloors with proper anchors, and pull the complete permit before framing starts. A garage conversion ADU in San Diego typically runs $35,400 to $94,400.
New Detached ADU
New construction on a tight canyon-rim lot in San Diego isn’t a clearance problem; it’s a staging problem. We park our equipment where the neighbors can still get through, keep the site clean every evening, and schedule deliveries around narrow driveways in Golden Hill and Mission Hills. No blocked access, no stop-work orders.
Junior ADU & Interior Conversion
A junior ADU inside the existing envelope of a pre-WWII Craftsman bungalow avoids most hillside triggers. But old drain lines still matter. In San Diego’s 92102 through 92107 ZIP codes, we commonly replace aging galvanized or cast-iron lines while the walls are open, because a failed line behind a finished interior is a surprise with a date on it.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in San Diego
We install materials San Diego homeowners can look up by name. For hardscape that accompanies an ADU or room addition, we use Belgard and Techo-Bloc pavers, and we keep Quikrete products stocked on the truck for San Diego’s coastal conditions. Marine layer moisture a mile from the ocean in 92107 and 92109 eats cheap hardware. We spec fasteners and materials that hold up west of the 5.
Common Home Additions & ADU Problems We See in San Diego Homes
- Canyon-lot foundations poured on decomposed granite: Original 1920s and 1930s foundations in Mission Hills and South Park frequently sit directly on granite fill over steep slopes with no engineered drainage. Any permitted addition triggers a soils report and Hillside Review.
- Coastal Zone permits doubling timelines: If the property falls within the California Coastal Zone, covering Ocean Beach 92107, Pacific Beach 92109, and coastal Point Loma 92106, a separate Coastal Commission permit adds months and design restrictions Chula Vista contractors never see.
- Shared party walls in North Park: Adding a second story on a 1920s bungalow often means working against a wall you share with a neighbor. One wrong anchor or a damaged stucco edge becomes a dispute and a stop-work order.
- Unpermitted rough-in from previous owners: We find buried electrical and plumbing work in additions all over San Diego. If the city never signed it off, it fails a re-sale inspection later. We fix it before it bites.
Pricing for Home Additions & ADU in San Diego, CA
We publish our starting ranges because San Diego homeowners deserve a real number before they sign anything. The allowance that isn’t on paper is a surprise waiting for a date.
| Project Type | Typical San Diego Range |
|---|---|
| Home Addition | $53,100 - $153,400 |
| ADU Construction | $106,200 - $259,600 |
| Garage Conversion | $35,400 - $94,400 |
What moves the number: hillside engineering, retaining walls, Coastal Zone review, sewer line upgrades on old lots, and whether we’re working on a tight lot with limited staging. Free estimates are exactly that. Call (877) 610-1318 and we’ll walk the site, look at the slope, and give you a written line-item quote.
We Also Serve Cities Near San Diego
Our crews cover the neighborhoods of San Diego every day, and we work the surrounding areas too: Lemon Grove, La Mesa, Coronado, and National City. The canyon-lot rules change the moment you cross the city line, and we know which side of that line your project sits on.
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
Almost always, yes. If the original foundation sits on decomposed granite fill over a steep slope, which is common in Mission Hills 92103 and South Park 92104, the City of San Diego will require a soils report and Hillside Review before any structural work begins. This is not a Chula Vista problem, and it’s not optional. Call (877) 610-1318 and we’ll tell you early whether your lot triggers it.
We start with a party-wall notice to the neighbor and a structural assessment before the first anchor goes in. Most 1920s bungalows in North Park share a wall line, and drilling into it without care creates cracks, disputes, and stop-work orders. We shore and protect the shared wall on every second-story addition. Call (877) 610-1318 for a site walk.
San Diego’s residential noise ordinance generally prohibits construction noise outside standard daytime hours, typically 7 a.m. to 7 p.m. on weekdays with more restrictions on weekends. We schedule loud work inside those hours and keep the site quiet at the edges so the neighbors stay reasonable. Call (877) 610-1318 and we’ll walk you through the schedule before the crew arrives.
Ocean Beach 92107 sits inside the California Coastal Zone, which means a separate Coastal Commission permit on top of the city’s building review. That review adds months and can restrict rooflines, setbacks, and materials. A garage conversion in North Park 92104 skips that layer entirely. The lot line changes the permit timeline, and we’ll tell you which one applies before you design around it. For an exact timeline on your property, call (877) 610-1318.
If the home still runs on original galvanized or cast-iron lines, which most pre-WWII South Park homes do, the added plumbing load from an ADU will usually trigger a city requirement to upgrade. We check the lines during the site walk and tell you what the inspector will ask for before you’re mid-project. Call (877) 610-1318 for a free estimate that includes the line check.
Working a Tight San Diego Lot Without Making Enemies
In San Diego’s canyon-rim neighborhoods, the hardest part of a home addition isn’t the framing. It’s staging. Mission Hills, North Park, South Park, Golden Hill: these are cut-and-fill lots where the street is narrow, the driveway is shared, and the neighbor’s kitchen window is ten feet from your property line. We park our equipment where it doesn’t block anyone’s garage, we keep materials stacked tight against the house, and we clean the site every single evening. A neighbor who can still get to their car is a neighbor who doesn’t call the city. That matters when your project is already facing Hillside Review.
Access shapes the quote too. If we’re building an addition at the back of a Golden Hill lot where the only crane access is through a 12-foot easement, that changes the structural approach before the first engineer’s stamp. We’ve built on slopes where the concrete had to be pumped 80 feet from the truck to the pour. We’ll tell you all of it up front, in writing, so the number doesn’t move on you later.
One Mission Hills job stays with us. A detached 1920s garage on a steep canyon edge, being converted into a permitted ADU. Our crew started by cutting a test hole at the slab, and what we found was exactly what the neighborhood kept warning us about: the slab was poured directly onto decomposed granite fill with no drainage beneath it. We installed an engineered retaining wall, added a new subfloor with proper anchors, and coordinated with the city’s Hillside Review division to keep the project moving while the neighbors’ access stayed clear. That’s the San Diego job, every time.
What You’ll Know After Reading This Page
- Adding an ADU or room addition on a canyon-rim lot in San Diego usually triggers a City of San Diego Hillside Review before framing begins.
- Properties in Ocean Beach 92107, Pacific Beach 92109, and coastal Point Loma 92106 face a separate California Coastal Zone permit that adds months.
- Home additions in San Diego run $53,100 to $153,400; ADUs run $106,200 to $259,600; garage conversions run $35,400 to $94,400.
- Every Barrett & Sons job includes permits pulled, written change orders before any scope change, and the 90-Day Done Right Promise.
- Free estimates with a written line-item quote mean the number you sign is the number you pay. Call (877) 610-1318.
If you’re planning a home addition or ADU in San Diego, start with a real site walk. We’ll look at the slope, the soil, the shared wall, and the permit path before you spend a dollar on design. Call (877) 610-1318 to schedule your free estimate.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving San Diego since 1998.