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 Daly City
A home addition or ADU in Daly City typically runs $45,000 to $130,000 for a room addition and $90,000 to $220,000 for a detached ADU, depending on site conditions, foundation work, and whether you’re building on a sloped Westlake lot. Most Daly City projects move through permitting in 6 to 16 weeks given the city’s specific seismic and hillside requirements. Barrett & Sons Construction is Tom Barrett’s owner-operated crew, founded in 1998, and we know Daly City’s Doelger-era housing stock block by block. Call us at (877) 610-1318 and let’s talk about what’s actually inside your walls before we quote you a number.
We’ve worked the hillside streets of Westlake, the flats of 94014, and the fog-heavy western slopes of 94015 long enough to know what’s behind the stucco before we open it. That local knowledge changes what a quote should say, and it changes what a finished addition actually costs you. If you live in Daly City, Home Additions & ADU work here starts with someone who’s seen your exact house a hundred times. Not a website that assumes every California home is the same.
Why Barrett & Sons Construction Is Daly City’s Preferred Home Additions & ADU Company
Tom Barrett puts his name, his address, and his license number on every contract he signs. Look it up before you sign anything. He lives twenty minutes from Daly City, and his sons run the crews that show up in the 94015 and 94014 ZIPs most weeks. When a Daly City homeowner calls us about a second-story addition on a sloped lot off Southgate Avenue, the person who answers the phone knows what a cripple-wall foundation is and why it matters on that block.
We carry our 90-Day Done Right Promise in writing on every home addition and ADU contract. If something’s not right, Tom comes back and makes it right. One call. That matters in Daly City, where the fog keeps testing exterior work and the hills keep testing foundations. Our Daly City customers know we pull permits and get inspections signed on every eligible job. The permit inspector works for you, not for me, and that’s exactly why we want him on the site.
Calls are answered by a live person 24/7, not a voicemail box and not an out-of-state call center. For Daly City homeowners in their 50s, 60s, and 70s who’ve been burned by a national company before, that detail alone is usually enough to get us in the door. But it’s the written change orders and the named material brands that keep us on the job.
Our Home Additions & ADU Services in Daly City
Second Story Additions in Daly City
A second-story addition in Daly City is not a simple framing job, and anyone who quotes it like one is guessing. The Doelger-era homes that dominate Westlake and the 94015 corridor were built with original 2×4 exterior walls that were never sized to carry an added floor’s load. We see this on nearly every hillside block. Before we frame a second story, we confirm the wall condition, check the cripple-wall foundation below, and bring the load path up to current seismic code. On sloped lots, that often means adding plywood sheathing and anchor bolts to the existing foundation first.
Garage Conversion ADU in Daly City
Daly City’s mid-century homes often have the garage tucked under the living space, a classic Doelger configuration. Converting that garage to an ADU in the 94015 ZIP usually starts with the slab. The original concrete was poured on grade without a vapor barrier, and Daly City’s persistent fog moisture wicks right through it. Left unaddressed, that rots new subflooring and bottom plates within a few seasons. We address it before we frame, and we write the scope and the allowance into your contract in plain language.
New Detached ADU in Daly City
A new detached ADU on a sloped Westlake lot requires careful site prep. The existing home’s cripple-wall foundation may need bracing before you set a second structure into the same hillside. Different settlement rates between the old house and the new ADU create cracks, sticking doors, and water intrusion if the site prep ignores what’s already in the ground. Our team handles the full ADU Site Prep & Utilities scope, from foundation and drainage to sewer and electrical service upgrades, before the first wall goes up.
Junior ADU & Interior Conversion in Daly City
A junior ADU, or JADU, lets you convert existing interior space, like a large bedroom or a partially finished lower level, into a legal living unit. In Daly City, where many Doelger homes have under-house garage space with low ceilings, a JADU can be the fastest path to rental income, but it still requires a permit and a separate entrance. We handle JADU design and permitting through Daly City’s specific requirements, and we work the same written-change-order process on a $45,000 JADU as we do on a $220,000 detached ADU.
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.
Trusted Brands We Service in Daly City
We install materials with names you can look up. For Daly City ADUs and additions, that often means Schluter waterproofing systems in the wet areas, GAF roofing and underlayment on the new roof planes, and Grohe fixtures in the bathroom or kitchenette. Every brand we use is a premium brand we stock locally, which means faster turnaround for Daly City customers and no mystery-brand materials pulled off a van. If you’re building a second-story addition on a fog-exposed elevation, the waterproofing brand matters, and we’re happy to explain why when we walk the site with you.
Common Home Additions & ADU Problems We See in Daly City Homes
- Soft-story cripple-wall foundations. Doelger-era homes in Westlake and the broader 94015 ZIP were built with garages under living space on sloped lots, creating the same under-floor geometry on block after block. These foundations were never engineered for seismic loads, and any addition that doesn’t address them first is adding load to a weak base.
- Fog-driven stucco delamination. Daly City sits in one of the densest fog belts in the Bay Area, and west-facing elevations take persistent marine moisture year-round. Stucco over lath delaminates, eave soffits rot, and mold moves into wall cavities faster than homeowners expect. Opening up a wall for an addition almost always reveals some of this.
- Original slab-on-grade garage floors without vapor barriers. Doelger garages were poured directly on the ground. Daly City’s fog keeps the soil beneath damp, and that moisture migrates up through the concrete. Any garage conversion that ignores this will fail at the subfloor and bottom plates.
- Undersized original framing on 2×4 exterior walls. The original walls of these mid-century tract homes were never meant to carry a second story. Framing an addition onto them without first verifying the load capacity causes sagging in the existing roof and cracked plaster in the living space below.
Pricing for Home Additions & ADU in Daly City, CA
You should know what the market actually costs before you sign anything. Here’s where Daly City lands for common addition and ADU scopes.
| Service | Typical Daly City Range |
|---|---|
| ADU Construction | $90,000 - $220,000 |
| Home Addition | $45,000 - $130,000 |
| Garage Conversion | $30,000 - $80,000 |
The spread exists for a reason. A ground-floor room addition on a flat 94014 lot is a different animal than a second-story addition on a sloped Westlake hillside with a soft-story cripple-wall foundation that needs bracing before the first framing nail goes in. Your allowance, your scope, and every price change arrives as a written change order before any work happens. That’s not a policy we put in a binder; it’s how Tom has run every job since 1998. Call (877) 610-1318 for a free estimate and we’ll give you a written line-item quote.
On a hillside block in the 94015 ZIP, our crew opened up a Doelger-era home for a second-story addition and found the original cripple-wall stem foundation had zero anchor bolts, and the T1-11 siding was delaminating from decades of fog-driven moisture. We wrote a change order for full cripple-wall bracing using the same plywood sheathing spec and anchor pattern we’ve installed hundreds of times across Westlake, then re-flashed the entire west-facing elevation before we framed the addition. That’s the difference between a quote prepared over the phone and a quote prepared by a contractor who’s been inside your neighbor’s house.
We Also Serve Cities Near Daly City
If you’re just over the border in Home Additions & ADU in Daly City or a neighboring community, we work the same owner-operated way. Barrett & Sons regularly serves homes across Visitacion Valley, South San Francisco, Noe Valley, and the Mission District. Same phone number, same crews, same written change orders. Call us and we’ll talk through your project.
Serving Daly City, CA - Our Local Coverage Area
We’re based in the Daly City 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 Daly City
The two we find most are missing or corroded anchor bolts in the cripple-wall foundation and fog-driven moisture damage at the eave soffits and west-facing stucco. We also routinely find original plaster that’s loose at the keys and wiring that predates current load requirements. When we open a wall and find something that changes the scope, you get a written change order with a price before we proceed. Call (877) 610-1318 if you’re planning to open yours up.
We price it in two parts: a fixed written scope for the known framing and finish work, and a written allowance for the foundation and seismic upgrades we may uncover once the walls are open. On a sloped Westlake lot, you should expect at least some cripple-wall bracing and anchor bolt work before we add a second story. That work gets priced and approved in writing before it begins, never as a surprise invoice at the end.
Yes, and the original slab is exactly why you want a contractor who’s done this in Daly City before. The slab was poured on grade without a vapor barrier, and Daly City’s fog keeps the soil beneath damp. We address that before we frame, with a vapor barrier and drainage plan that keeps moisture out of the new subfloor and bottom plates. The permit and the written change order cover it.
Yes. A JADU still requires a permit and a separate entrance, even when you’re converting existing interior space. Daly City’s permitting process for JADUs is specific, and we handle the filing and the inspection. We don’t do unpermitted work, and we won’t tell you a permit is optional because a previous contractor did. Call (877) 610-1318 for a free estimate on your JADU.
We spec the waterproofing and flashing for Daly City’s specific moisture load, not for an inland California climate. That means full re-flashing on west-facing elevations, proper drainage planes behind the cladding, and materials like GAF underlayment that stand up to persistent marine moisture. The fog doesn’t stop, so neither does the water management. That’s built into the written scope, not left to hope.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Daly City and the Bay Area since 1998.