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 Hermosa Beach
Home additions and ADU construction in Hermosa Beach run $45,000-$130,000 for a second-story addition and $30,000-$220,000 for garage conversions or detached ADUs, and almost every project in the city needs a Coastal Development Permit from the California Coastal Commission before any wall gets opened. That’s the part most contractors gloss over until it’s too late. We’re Barrett & Sons Construction, and we’ve been planning around Hermosa Beach’s coastal zoning, narrow alleys, and view-preservation rules long enough to tell you exactly what your project will trigger before demolition starts. Call (877) 610-1318 and we’ll walk your lot with you.
Why Barrett & Sons Construction Is Hermosa Beach’s Preferred Home Additions & ADU Company
Tom Barrett put his name on the truck in 1998, and his sons run the crews that work Hermosa Beach streets like The Strand, Pier Avenue, and the alleys behind 14th Street and 24th Street. You’ll see our teams moving materials by hand down those 10-foot-wide back alleys because we know a dumpster won’t fit, and we know the city’s encroachment permit process cold. Homeowners in the 90254 zip code call us because we hand them a written scope, written allowances, and written change orders before anything changes, not after.
Our Home Additions & ADU team has handled permit reviews with the California Coastal Commission, planned second-story builds around view corridors, and rescued projects other contractors abandoned at inspection. If something doesn’t pass, Tom comes back. That’s the 90-Day Done Right Promise, written on every contract. No fine print, no phone tag. You call, a live person answers, Tom shows up.
Our Home Additions & ADU Services in Hermosa Beach
ADU Design & Permitting
Every ADU in Hermosa Beach starts with two permission slips: the city’s planning review and the California Coastal Commission’s Coastal Development Permit. We run both. Our team documents your lot’s existing footprint, the alley access if you have one, and the height limits triggered by your street’s view corridor. You get a permit package that’s ready for review, not a folder of unanswered questions. A completed detached ADU in Hermosa Beach typically runs $90,000-$220,000 depending on the foundation work and the Coastal Commission’s conditions.
Garage Conversion ADU
Converting a detached garage into an ADU in Hermosa Beach runs $30,000-$80,000 and it’s the most common way to add rental income because the structure already exists. The catch here is the alley. If your garage only opens to a 12-foot alley off 14th or Manhattan Avenue, a concrete truck can’t park there without a temporary encroachment permit from the city, and sometimes not even then. We schedule the pour around city approval, and if a pump truck is required, that’s written in as a line-item before you sign anything.
New Detached ADU
Building a new detached ADU on a Hermosa Beach lot means engineering for the sandy coastal soils and the liquefaction zone the entire city sits in. A slab from the 1950s won’t support a new structure without reinforcement. We pour engineered foundations with the right rebar and tie-downs for the seismic requirements. Then we frame with materials that can take the marine layer: stainless fasteners, hot-dipped galvanized hardware, and exterior treatments specified for salt air. A new detached ADU runs $90,000-$220,000.
Junior ADU & Interior Conversion
A Junior ADU converts existing interior space, like a spare bedroom or a basement, into an independent living unit. In Hermosa Beach, the Coastal Commission still has a say if the conversion changes the exterior or adds a separate entrance. We plan Junior ADUs around the city’s interior square footage limits and the view-preservation rules that apply to any exterior modification. This service pairs well with a Home Additions & ADU in Hermosa Beach consultation because the feasibility depends on your specific floorplan and your lot’s coastal zone designation.
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 Hermosa Beach
We install brands you can look up, not materials off a random van. For Hermosa Beach projects, we frequently specify Schluter waterproofing systems because the marine layer and coastal humidity will find any gap in a shower or tub surround. Sterling fixtures and Grohe plumbing hold up better against the salt air than cheaper chrome finishes do. If you have a brand preference, we’ll write it into the scope and the allowance. You won’t get a mystery substitute at the rough-in stage.
Common Home Additions & ADU Problems We See in Hermosa Beach Homes
- Knob-and-tube wiring hiding behind 1920s lath and plaster. Once you open a wall for a second-story addition, the city’s current electrical code applies to the space you’re modifying, and the old wiring has to go. We write an allowance for rewiring in the original contract so it doesn’t blindside you at the rough-in inspection.
- Dry-rotted sill plates from decades of marine-layer moisture. The original beach cottages along The Strand and the avenues have wooden sills sitting inches above sandy soil. When we open the wall, that plate is often compromised, and the permit mandates a new tie-down to the foundation anyway.
- Alley-only access that kills crane and concrete truck access. Many Hermosa Beach parcels have no street frontage for a big truck. A second-story addition’s framing lumber or a new ADU’s concrete pour has to be staged on the street and hand-carried. We build encroachment permit time into the schedule from day one.
- View-preservation height limits that change your roofline. The Coastal Commission’s height caps on 25-30-foot-wide lots often mean a second-story addition has to step back or pitch a certain way. We submit drawings that account for this before you pay for engineering.
Pricing for Home Additions & ADU in Hermosa Beach, CA
We quote real numbers, in writing, before any work starts. Hermosa Beach’s permit process is the single biggest variable most contractors leave out of their estimate, and we won’t do that to you. Here’s what our customers in this market actually pay:
| Project Type | Typical Range in Hermosa Beach |
|---|---|
| Second Story Addition (Home Addition) | $45,000-$130,000 |
| Detached ADU Construction | $90,000-$220,000 |
| Garage Conversion ADU | $30,000-$80,000 |
The biggest cost drivers are the Coastal Development Permit timeline, foundation work in the liquefaction zone, and the aluminum, stainless, or hot-dipped galvanized hardware required to survive salt air. Every allowance is on paper. Every change order is in writing before it happens. Call (877) 610-1318 for a free estimate with actual line-items, not a phone quote that changes at the door.
What a Hermosa Beach Coastal Development Permit Triggers Once You Open the Wall
Virtually every Home Addition & ADU project in Hermosa Beach sits within the California Coastal Zone, which means the California Coastal Commission reviews your project in addition to city planning. That’s a dual-approval process that adds months to the timeline and imposes view-preservation height limits on the city’s narrow 25-30-foot lots. Here’s what that means in practice: a second-story addition doesn’t just need to clear city building and safety. It needs to satisfy a Coastal Commission reviewer looking at your roofline’s impact on your neighbors’ ocean views. We prepare the drawings, the view-corridor analysis, and the permit package knowing the reviewer’s questions before they ask them. That’s the difference between a project that stalls for eight months and one that moves.
On a 1920s beach cottage off the 14th Street alley, our crew opened the wall for a second-story addition and found knob-and-tube wiring and dry-rotted load-bearing sill plates from decades of marine-layer moisture. We stopped the rough-in, wrote a change order with allowances for new subfloor and Simpson ties, and after inspection sign-off, rebuilt the framing with hot-dipped galvanized hardware before closing the wall. The homeowner never got a surprise invoice. He got a written change order with a price, a reason, and his signature on it before we touched anything.
We Also Serve Cities Near Hermosa Beach
Our crews work all over the South Bay. You’ll find us on projects in Redondo Beach, Marina del Rey, Palos Verdes Estates, and Lawndale, where the permit rules and lot geometry are a little different but the standard is the same. If you’re in one of those cities, call (877) 610-1318 and ask for Tom’s team directly.
Serving Hermosa Beach, CA - Our Local Coverage Area
We’re based in the Hermosa Beach 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 Hermosa Beach
Yes. Almost every second-story addition in Hermosa Beach requires a Coastal Development Permit from the California Coastal Commission because the city sits almost entirely within the Coastal Zone. The review runs in parallel with city permits and adds months to the timeline. We handle both applications and submit the drawings in the format the Coastal Commission expects.
Usually not without a city-issued temporary encroachment permit, and sometimes not even with one. For a 12-foot alley, we often specify a pump truck or stage the pour from street access if your lot has it. We write the access plan and the encroachment permit timeline into the contract before the first day of work. Call (877) 610-1318 and we’ll walk your alley with you.
We stop work, document the extent of it, and write a change order with the allowance for rewiring that was already in your contract. The city’s current electrical code requires the old wiring be removed from any space we’re modifying. You approve the change order in writing before we proceed. You’ll never get a bill for work you didn’t approve.
The Coastal Commission enforces view-corridor rules that limit the roofline’s height and pitch on many Hermosa Beach streets. Your design may need to step back from the ocean-facing side or use a lower-pitch roof than you originally planned. We design within those limits from the start, so you’re not paying for engineering drawings that get rejected at review.
Almost always, yes. Hermosa Beach sits in a seismic liquefaction hazard zone with sandy coastal soils, and a slab from the 1950s won’t support the added load of a second story. We engineer a new foundation or a substantial retrofit with tie-downs and reinforcement specified for the soil conditions. It’s written into the scope and the price before work starts. For an exact quote on your specific lot, call (877) 610-1318.
Get Your Free Hermosa Beach Home Addition Estimate
Tom Barrett’s name, his address, and his license number are public, and he’ll give them to you before you sign anything. You’ll get a written scope, written allowances, and written change orders before work proceeds. No surprise invoices at the end. No permits skipped. No mystery brands off the back of a van. Call (877) 610-1318 today for a free estimate, or ask for Tom’s second opinion on any written estimate you’ve already received from another contractor.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Hermosa Beach and the South Bay.