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
Home additions and ADU construction in Laguna Hills typically run $45,000 to $130,000 for an addition and $90,000 to $220,000 for a new detached ADU, with garage conversions landing between $30,000 and $80,000. Those are real numbers for this market, and they shift based on what’s under your house more than what’s above it. If you’re planning a room addition or an ADU on a Laguna Hills lot, call Barrett & Sons Construction at (877) 610-1318 and we’ll talk through what your specific property actually needs. We’ve been opening walls in this city long enough to know what’s waiting behind them.
Key Takeaways:
- Expect code-triggered upgrades when working on 1970s-80s Laguna Hills tract homes - we document every one in writing before work proceeds.
- Downslope rear-yard ADUs on old fill may require helical piers or over-excavation - we’ll tell you before you spend a dollar.
- Free estimates for Home Additions & ADU in Laguna Hills - call us, Tom picks up.
Why Barrett & Sons Construction Is Laguna Hills’s Preferred Home Additions & ADU Company
Tom Barrett founded this company in 1998, and his name is still on the truck and the contract. That matters in Laguna Hills because so much of the work here requires judgment calls that a franchise estimator can’t make. When we walk a property off El Toro Road and see a tilted retaining wall at the rear lot line, we know what that means before we ever put a shovel in the ground. Our Home Additions & ADU team has opened enough Laguna Hills homes to recognize the framing patterns from that building era, and we plan for them from the first site visit.
We answer our own phone, day or night, at (877) 610-1318. When you call about an addition in 92653 or a garage conversion in 92654, you’ll talk to someone who has actually stood in those neighborhoods. Not a call center. We treat every permit as non-negotiable in Laguna Hills because the city’s building department will inspect what you opened, and retrofitting a non-strapped cripple wall after the fact costs three times what doing it right the first time does. We’d rather tell you that before you sign than after the inspector leaves.
Every contract we write includes our 90-Day Done Right Promise. If something isn’t right, one call brings Tom back. And every scope change, every allowance, and every price adjustment arrives as a written change order before a single nail moves. The owner’s sons run the crews on most Laguna Hills jobs, and that’s who shows up at your door with a background check and a Barrett & Sons uniform.
Our Home Additions & ADU Services in Laguna Hills
ADU Design & Permitting
The City of Laguna Hills wants to see plans, soils reports where the lot demands them, and compliance with current state ADU law. We handle the full design and permitting path for detached ADUs, garage ADUs, and Junior ADUs, including the High Fire Hazard Severity Zone requirements that add WUI-compliant materials and ember-resistant vents to your project. What most people don’t know is that a permit on a downslope lot off Paseo de Valencia often triggers a soils investigation the original 1970s builder never had to do. We’d rather know that before plans go in.
Garage Conversion ADU
Garage conversions are the most common way Laguna Hills homeowners add a rental unit without sacrificing yard space. They usually run $30,000 to $80,000, but a conversion in this city frequently uncovers original post-tension slab conditions that require structural evaluation before we can frame interior walls. Your 1980s garage wasn’t built as living space. When we convert it, we bring the electrical, insulation, ventilation, and egress up to current code, and we write every one of those upgrades into a change order before work starts.
New Detached ADU
A new detached ADU in Laguna Hills is a fresh build, but it’s still tied to the land it sits on. If your rear yard is on the fill side of a cut-and-fill pad, we may need to over-excavate or specify helical piers to keep the slab from cracking in five years. Those calls add real cost and we’ll tell you upfront. Our crews have built detached units from 400 to 1,200 square feet in neighborhoods across 92653 and 92654, including ones that required retaining wall replacement before the first form was set.
Junior ADU & Interior Conversion
A Junior ADU inside your existing floor plan is often the lowest-cost path to a legal second unit - and because it doesn’t add foundation area, it can avoid some of the soils issues that drive cost on hillside lots. But if the conversion touches load-bearing walls or opens original framed areas that predate modern Orange County seismic code, the inspector can require a strap-and-plywood upgrade on the existing cripple walls. We walk you through what triggers that and what doesn’t, before you commit. Interior conversions typically stay well under the six-figure mark while still producing a rent-ready unit.
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 stock and install materials that carry names you can look up. For ADU bathroom and wet-area waterproofing we use Schluter systems, and for plumbing fixtures we lean on Grohe and Sterling - brands designed to survive the wet-dry cycle that punishes cheap hardware on a hillside. On ADU roofs and tie-ins to existing structures we use GAF underlayment and shingles, which matters in a High Fire Hazard Severity Zone where the city requires Class A materials. When a Laguna Hills homeowner asks what we’re putting in their home, we can hand them a spec sheet with a real brand name on it, not a mystery off a van.
Common Home Additions & ADU Problems We See in Laguna Hills Homes
- Settled fill beneath rear-yard additions and ADUs. Original 1970s grading along the Paseo de Valencia and El Toro Road corridors often left downslope fill that was never compacted to modern standards. We’ve watched patios drop inches from the house foundation over a few rainy seasons, and any addition that ties into that area has to account for movement.
- Non-earthquake-strapped cripple walls on original tract framing. Homes built before current seismic codes often have cripple walls with no plywood shear. Opening a wall for a room addition triggers an inspection, and the inspector will flag it. We plan for that retrofit in our original quote, not as a surprise.
- Undersized headers on load-bearing walls. We commonly find original 1980s headers sized by standards that no longer pass. When your new addition’s roofline meets the old one, the existing header often has to come out and get replaced. We document it, price it, and get your signature before saws come out.
- Expansive clay swelling and shrinking through wet winters and dry summers. Laguna Hills sits on clay that changes volume with moisture. Poor drainage on the cut side of a lot can saturate that clay and heave a new ADU slab in a single winter. Our drainage plans route water away from the foundation, not toward it.
Pricing for Home Additions & ADU in Laguna Hills, CA
No amount of national averaging tells you what your project costs. In Laguna Hills, your real number depends on slope, fill condition, fire-zone requirements, and what code inspectors find when the walls come open. Here are line-item ranges from jobs we’ve built in this city:
| Project | Typical Laguna Hills Range |
|---|---|
| Home Addition | $45,000 - $130,000 |
| ADU Construction | $90,000 - $220,000 |
| Garage Conversion | $30,000 - $80,000 |
Those ranges narrow once we see your lot. A flat interior addition on a home without seismic flags will sit at the lower end. A detached ADU on a settling rear yard with a required retaining wall will push toward the top. We give you a written, line-by-line estimate, and if something changes during the job, you get a written change order with a number on it before we proceed. Call (877) 610-1318 for a free estimate and we’ll come walk your property.
We Also Serve Cities Near Laguna Hills
Barrett & Sons Construction serves homeowners across Laguna Hills and the surrounding communities - Laguna Woods, Lake Forest, Mission Viejo, and Coto De Caza. If you live just across the city line and have the same 1970s tract construction, the same cut-and-fill pads, and the same inspector questions, we know your area too. Give us a call and we’ll come take a look.
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
They change because the home was built before current code, and the inspector requires upgrades once those walls are exposed. A typical 1980s tract home in Laguna Hills has a non-strapped cripple wall and undersized headers in load-bearing locations. Our quotes include an inspection allowance, and any code-triggered upgrade arrives as a written change order with a specific price before we touch it. Call (877) 610-1318 and we’ll explain what to expect on your specific house.
Yes. Downslope yards along Paseo de Valencia and El Toro Road often sit on poorly compacted 1970s fill, and the city frequently requires a soils report before issuing an ADU permit. If the report shows settlement-active soil, you may need helical piers, over-excavation, or both - which changes the foundation budget significantly compared to a flat Mission Viejo lot. We’ll walk the yard with you and tell you what we see before you commit.
It mandates Class A roofing, ember-resistant venting, and WUI-compliant construction materials on any new structure or re-roofed area. Those materials cost more and sometimes carry longer lead times than what’s allowed in lower-risk adjacent cities. We factor fire-zone compliance into our original estimate so you’re not surprised when the plans come back from review.
Expect the inspector to look at the electrical rough-in, framing, insulation clearance, and most importantly the slab and cripple wall conditions in a converted garage. If the original post-tension slab shows cracks from fill movement or the walls lack shear, the inspector can stop work until those items are addressed and re-inspected. We walk each rough-in inspection with you, and any correction gets priced in writing before we proceed.
Often yes, because a JADU inside the existing envelope doesn’t add foundation area and may not trigger a soils report. But if the conversion opens load-bearing areas with original unstrapped framing, the inspector can still require a cripple wall retrofit in that section. We’ll tell you honestly whether your JADU stays simple or triggers more, and we’ll put it in writing either way. Call (877) 610-1318 for a free assessment.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Laguna Hills since 1998.