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 Bruno
A full home addition or detached ADU in San Bruno typically runs $45,000 to $130,000 depending on scope, lot slope, and whether your property falls inside the PG&E enhanced-locate corridor near Crestmoor. On a hillside lot, budget on the higher end. The good news is the work is done right, permitted, and backed by a written 90-Day Done Right Promise.
Barrett & Sons Construction has served San Bruno homeowners for years from our Bay Area office, and Tom Barrett’s sons run the crews that show up at your door. We know the wind-gap building requirements, the Crestmoor dig permit timelines, and the hillside retaining wall math that most contractors don’t price until it’s too late. Call (877) 610-1318 for a free, written estimate before you sign anything.
Why Barrett & Sons Construction Is San Bruno’s Preferred Home Additions & ADU Company
We’re not the cheapest bid in San Bruno. We’re not trying to be. Homeowners in the 94066 zip code call us because Tom Barrett puts his name, address, and license number on every contract, and when you call, a live person answers. Not a voicemail box. Not an out-of-state call center.
Our Home Additions & ADU team has done more than frame walls and pour footings in San Bruno. We’ve navigated the PG&E enhanced-locate process near Crestmoor while the previous contractor on the same project got a stop-work notice and walked away. We’ve submitted engineered wind-load calculations for second-story additions on properties buffeted by San Bruno Gap gusts that a standard Peninsula nailing schedule won’t pass. We know that in San Bruno, every scope change, every allowance, every price adjustment arrives as a written change order before a single nail moves. That’s how Tom has run the company since 1998.
Background-checked, uniformed crew members carry the Barrett & Sons name. If the permit inspector has questions, Tom answers them himself. Ask anyone on your street, or look up the license number yourself.
Our Home Additions & ADU Services in San Bruno
New Detached ADU
A detached accessory dwelling unit on a San Bruno hillside lot is not the same job as one in flatland Millbrae. San Bruno’s post-WWII ranch homes sit on sloped parcels where you’ll likely need retaining walls, engineered drainage, and in some cases a foundation system designed for wind uplift. We scope all of that before you sign. A new detached ADU in San Bruno generally starts around $90,000 and can reach $220,000 for a fully finished unit with premium fixtures. Our team handles the set of site challenges here better than anyone, because we’ve already built on these exact lots.
ADU Site Prep & Utilities
In San Bruno, site prep is not a line item you want priced with a guess. If your property falls within roughly a mile of the 2010 Crestmoor blast zone, any excavation or utility work triggers PG&E’s post-explosion enhanced locate and verification process. That routinely adds 3 to 5 business days versus a standard 811 call elsewhere on the Peninsula. We build that lead time into the schedule up front, so you’re not standing in your yard wondering why the dig crew hasn’t arrived.
Garage Conversion ADU
Converting a 1950s San Bruno garage into livable square footage usually runs $30,000 to $80,000. The big question on these older garages is whether the slab, the electrical, and the sewer tie-in will pass today’s code. In San Bruno, many of those original slabs were poured without rebar or vapor barriers. We test before we quote, and we put every allowance in writing.
Junior ADU & Interior Conversion
A junior ADU carved out of an existing San Bruno home is often the fastest path to rental income or a comfortable space for an aging parent. These projects run from the lower end of the $45,000-to-$130,000 range depending on whether you’re converting a finished bedroom suite or reworking plumbing in an unconditioned attic. San Bruno’s compact split-level layouts sometimes require creative access planning, but we’ve managed it on plenty of side streets across 94066.
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 San Bruno
When we build a detached ADU or a second-story addition in San Bruno, we install brands you can look up. We regularly work with Quikrete and Oldcastle products on the foundation and hardscape side, and when a paver patio or driveway accompanies a garage conversion, Techo-Bloc and Cambridge Pavers are go-to options for San Bruno’s exposed coastal conditions. We stock the parts and materials our San Bruno customers need locally, which means fewer delays when the weather window closes or the inspector schedules a next-day revisit.
Common Home Additions & ADU Problems We See in San Bruno Homes
- Stop-work notices on dig permits near Crestmoor. Contractors who assume a standard 811 locate will clear any excavation within a mile of the 2010 blast zone learn otherwise fast. We pre-file the enhanced PG&E verification paperwork before the first shovel hits the ground.
- Wind-load failures on second-story additions. San Bruno sits in the San Bruno Gap, a natural wind channel through the Coast Range. Sustained winds here are measurably stronger than in Millbrae or Burlingame, and second-story framing that passes inspection elsewhere won’t pass in 94066 without engineered wind-load calculations.
- Hillside retaining wall and drainage overruns. A lot that looks flat from the street can drop six feet in the back. On San Bruno’s sloped post-WWII lots, a detached ADU without a retaining wall and drainage allowance can end up with a change order that equals the original framing budget.
- Legacy gas lines nobody knows about. The Crestmoor rebuild created an unusual patchwork of 60-year-old originals next to code-current homes. We’ve hit abandoned gas service stubs on properties that had no record of them. That’s exactly why we dig after the enhanced locate, not before.
Pricing for Home Additions & ADU in San Bruno, CA
| Project | Typical San Bruno Range |
|---|---|
| Home Addition | $45,000 - $130,000 |
| ADU Construction | $90,000 - $220,000 |
| Garage Conversion | $30,000 - $80,000 |
Every price we quote in San Bruno includes permits pulled and inspections signed, written change orders before any scope change, and the 90-Day Done Right Promise written on the contract. Call (877) 610-1318 for a free line-item estimate.
We Also Serve Cities Near San Bruno
We work across the northern Peninsula from San Bruno out to Millbrae, South San Francisco, Pacifica, and Burlingame. If you’re a few minutes up El Camino Real or over the hill toward the coast, the same crew, the same written pricing, and the same owner-operated standard applies.
Serving San Bruno, CA - Our Local Coverage Area
We’re based in the San Bruno 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 Bruno
Any excavation within roughly a mile of the Crestmoor blast zone triggers PG&E’s enhanced locate and verification process, which typically adds 3 to 5 business days to the dig permit timeline versus a standard 811 call elsewhere in San Mateo County. We build that lead time into the schedule before you sign, so the crew isn’t standing around while the clock runs. Call (877) 610-1318 for a timeline specific to your San Bruno property.
Plan for retaining walls, engineered drainage, and a foundation designed for slope stability. On San Bruno’s post-WWII hillside lots, a detached ADU without those allowances can produce a change order that equals the original framing budget. We write the grading and subfloor allowances into your contract before the first stake goes in the ground, and every allowance arrives in writing.
San Bruno sits in the San Bruno Gap, a wind channel that produces sustained winds measurably higher than Millbrae or Burlingame. A second-story addition here requires engineered wind-load calculations and a different fastening schedule than the standard Peninsula detail. That’s an engineering cost, not a markup. Call (877) 610-1318 and we’ll show you exactly where the money goes.
Only if the garage conversion involves no excavation or utility tie-in within about a mile of the Crestmoor blast zone. In practice, most San Bruno garage conversions need a sewer tie-in or electrical trench, which is excavation and likely does trigger the enhanced process. We check the map before we quote, so you know what you’re facing in writing.
Put the scope, the price, the line-item allowances, the permit status, and the change order process in writing before you sign. Every San Bruno project we quote includes a written line-item estimate, permits pulled and inspections signed, and a written change order before any scope change touches the job. The allowance that isn’t on paper is a surprise waiting for a date. Call (877) 610-1318 for a free estimate and we’ll walk you through it.
Ready to get a number you can hold us to? Call Barrett & Sons Construction at (877) 610-1318 to schedule your free estimate for a home addition or ADU in San Bruno. Tom or one of his sons will answer.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving San Bruno since day one.