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 Laguna Hills
A full home addition or ADU in Laguna Hills generally runs $45,000 to $130,000 for an attached addition and $90,000 to $220,000 for a detached ADU, with garage conversions landing between $30,000 and $80,000. That’s a wide band because opening up a 1970s hillside tract home almost always turns up something unexpected: undersized headers, settling slabs, or wiring that predates current code. Our Home Additions & ADU team has spent nearly three decades working exactly these homes, and we price the unknowns upfront with written allowances, so the number you sign is the number you can trust. If you’re planning a room addition, second story, or ADU in Laguna Hills, call us at (877) 610-1318 and we’ll walk the property with you before anything goes on paper.
Why Barrett & Sons Construction Is Laguna Hills’s Preferred Home Additions & ADU Company
Tom Barrett founded Barrett & Sons Construction in 1998, and his sons run the crews you’ll see in Laguna Hills. That’s not marketing copy. Tom answers his own phone, and the crew members who show up carry the Barrett name and wear the Barrett uniform. Homeowners in 92653 and 92654 have called us after a national outfit quoted one price on the phone and handed them another at the door, and the difference they notice first is simple: every scope, every allowance, every price change arrives as a written change order before a single nail moves.
We pull permits and get inspections signed on every eligible addition or ADU job in Laguna Hills. The permit inspector works for you, not for us. That’s why we schedule the inspection, walk it with the inspector, and don’t close a wall until the City of Laguna Hills signs off. Our 90-Day Done Right Promise is written on every contract: if something isn’t right, one call brings Tom back. We also publish Tom’s name, address, and license number. Look it up before you sign anything.
Our Home Additions & ADU Services in Laguna Hills
When you’re adding square footage in Laguna Hills, the house’s age and hillside setting shape the job as much as the floor plan does. These are the four services homeowners ask us about most.
ADU Design & Permitting
Laguna Hills sits within California’s High Fire Hazard Severity Zone, which means a detached ADU or garage conversion has to meet WUI (Wildland-Urban Interface) requirements: ember-resistant vents, Class A roofing, and specific exterior materials. We handle design, structural review, and the permit set so your ADU passes the City of Laguna Hills plan check and final inspection on the first pass. The cost of a permitted ADU in Laguna Hills typically runs $90,000 to $220,000, and that includes the soils report, structural engineering, and the fire-hardening upgrades the city requires.
Garage Conversion ADU
Converting an attached garage is usually the most cost-effective ADU route in Laguna Hills, running $30,000 to $80,000. The catch is that most 1970s garages weren’t built with habitable-space insulation, moisture barriers, or the ember-resistant venting the fire zone requires. We open the walls, confirm what’s actually there, and write the corrections into the scope before we touch the framing. You get a livable unit and a final inspection the city signs off on.
New Detached ADU
A detached ADU on a hillside lot in Laguna Hills starts with the soils question. Much of the city was graded as cut-and-fill during the 1970s and 80s, and fill sides were often compacted to looser standards than modern code allows. We order a soils report, design footings to match what the report shows, and build the ADU so it won’t settle away from the main house. Detached ADU construction in Laguna Hills typically runs $90,000 to $220,000.
Junior ADU & Interior Conversion
A junior ADU, or JADU, converts existing interior space, like a large bedroom or bonus room, into an independent living unit with its own entrance and kitchenette. These projects run tighter permit schedules than ground-up builds, and they’re a practical option for Laguna Hills homeowners who want rental income or multi-generational living without new foundation work. We handle the occupancy-triggered upgrades, including egress windows, smoke and CO detection, and the separate utility metering the city requires.
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 Laguna Hills
We install brands you can look up, not mystery materials off a van. For ADU kitchens and baths, we use Schluter waterproofing systems under tile and Sterling or Grohe fixtures where the spec calls for them. On ADU and addition roofs, we use GAF roofing systems rated for the High Fire Hazard Severity Zone. Because we stock common parts for these brands and work with local Laguna Hills suppliers, material delays are shorter than they’d be with a crew that doesn’t know the area.
Common Home Additions & ADU Problems We See in Laguna Hills Homes
- Uneven settlement on cut-and-fill pads. The original 1970s grading in parts of Laguna Hills left fill sides that weren’t fully compacted to modern standards. A new room or ADU added on the fill side can settle differently than the original house, cracking the slab and racking the framing. We order soils reports before we design footings.
- Undersized headers found when walls open. Many original Laguna Hills tract homes were framed with headers that met the minimums of their day but fall short of current Orange County building code. When we open a load-bearing wall for a room addition, we frequently find a header that needs to be replaced with a larger LVL before the wall can be closed.
- Original post-tension slabs with hairline cracks. Clay soils in Laguna Hills swell in wet winters and shrink in dry summers, which puts annual stress on the post-tension slabs under many 1970s homes. Adding a second story without evaluating the slab can overload it. We inspect, document, and write the repair scope into the contract as an allowance.
- Missing ember-resistant venting and WUI upgrades. Homes built before current fire-zone requirements often have vents and exterior details that don’t meet the Wildland-Urban Interface standards the City of Laguna Hills now enforces. On additions and ADUs, the permit triggers those upgrades, and we include them in the written scope so they don’t show up as an end-of-job surprise.
Pricing for Home Additions & ADU in Laguna Hills, CA
Here’s the honest breakdown for Laguna Hills. The table below reflects what we see across the city’s hillside tract stock, including the structural and fire-zone upgrades that most jobs trigger.
| Project Type | Typical Price Range in Laguna Hills |
|---|---|
| Home Addition | $45,000 - $130,000 |
| ADU Construction | $90,000 - $220,000 |
| Garage Conversion | $30,000 - $80,000 |
The biggest cost drivers in Laguna Hills are the soils report and foundation work on cut-and-fill pads, the fire-hardening upgrades the High Fire Hazard Severity Zone requires, and the structural corrections that come to light when walls open. That’s exactly why we write allowances into every contract. If we open a wall along Paseo de Valencia and find a cracked slab or an undersized header, the repair is priced and approved in writing before we proceed. Call (877) 610-1318 for a free estimate with line-item pricing. We also offer a free second opinion on any written estimate, no trip charge inside the county, and a permanent 10% senior and veteran discount.
We Also Serve Cities Near Laguna Hills
Our crews work throughout south Orange County, including Laguna Hills and the surrounding communities. Neighboring cities we serve include Laguna Woods, Lake Forest, Mission Viejo, and Coto De Caza. Many of our Laguna Hills clients call us first and then refer us to family across these nearby cities. Same ownership, same written change orders, same 90-Day Done Right Promise.
Serving Laguna Hills, CA - Our Local Coverage Area
We’re based in the Laguna Hills 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 Laguna Hills
Opening a load-bearing wall in a 1970s Laguna Hills home triggers current Orange County structural code, which usually means replacing the original undersized header with a larger engineered LVL, adding hold-downs and strapping if they’re missing, and upgrading any non-conforming electrical, insulation, or fire-blocking inside the opened cavity. On an exterior wall, the permit also triggers the ember-resistant venting and WUI exterior requirements tied to the city’s High Fire Hazard Severity Zone. We walk you through every triggered upgrade before the wall is opened, then price each one as a written line item. Call (877) 610-1318 to schedule a free walkthrough of your addition.
Laguna Hills lots were largely graded as cut-and-fill during the 1970s and 80s, and the fill sides were often compacted to looser standards than modern code allows, which means decades of clay-soil heave and uneven settlement have left hidden damage behind the drywall. When we open framing on a hillside tract home, we regularly find hairline post-tension slab cracks, undersized headers, and non-strapped cripple walls that a flatter city doesn’t see as often. That’s why we write allowances into every contract: the unknown is priced and approved in writing before we spend your money on it, so the final number never shows up as a surprise invoice.
Downslope rear yards along the El Toro Road corridor often sit on fill that was never fully compacted to modern standards, which means the new ADU’s roof drainage has to be designed carefully to avoid concentrating water against the existing fill-side retaining wall. If water sheeting off a new roof is allowed to pool against that wall, it tilts further and floods the crawl space within a season or two. We grade the ADU’s drainage away from the fill side, install proper surface drainage, and rebuild or reinforce the retaining wall if it’s already leaning. A soils report drives those decisions, not guesswork.
A detached ADU in Laguna Hills requires a full foundation design with a soils report, while a garage conversion works within the existing slab, so the detached build triggers a longer plan-check and structural review at the City of Laguna Hills Community Development counter. Both trigger the High Fire Hazard Severity Zone upgrades, but a detached ADU also requires Class A roofing, ember-resistant vents, and defensible-space-compliant exterior materials from the ground up. A garage conversion typically costs $30,000 to $80,000, while a detached ADU runs $90,000 to $220,000. We handle the full permit set for both. Call (877) 610-1318 for a free estimate.
Yes, but the post-tension slab has to be evaluated before any second-story framing starts, because the clay soils under many Laguna Hills homes have already stressed those slabs through decades of wet-dry cycling. A second story adds concentrated load to the existing footings and slab, and cut-and-fill pads can settle unevenly under that new weight, cracking the slab and racking the original framing. We order an inspection and often a soils report, then reinforce or add footings where the report tells us to. The structural work gets written into the contract as an allowance and signed off by the city inspector before we close anything.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Laguna Hills and the surrounding communities.
Planning a home addition or ADU in Laguna Hills? Call (877) 610-1318 today to schedule your free estimate. We’ll walk the property, explain what the permit will trigger, and put every dollar in writing before we start.