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 Orange
Home additions and ADU construction in Orange typically run $45,000-$130,000 for an addition and $90,000-$220,000 for a detached ADU, with permits and design shaping the final number more than any other single factor. That range reflects the reality of building in a city where Old Towne historic review, county permit zones on acreage, and hillside drainage each carry their own costs and timelines. If you’re planning a second story, a garage conversion, or a new detached unit off Cannon Street or Chapman Avenue, you’ll want a contractor who knows Orange’s specific rules before the first drawing leaves the table. Call (877) 610-1318 to schedule a free estimate. We’re Barrett & Sons Construction, and we’ve been answering our own phone since 1998.
Orange isn’t a single building environment. The Orange you live in might be a 1912 Craftsman in Old Towne, a 1960s ranch on a flat slab near Tustin Avenue, or a graded hillside lot off Cannon Street in the 92862 ZIP. Each one changes how we scope, permit, and price your Home Additions & ADU project. This page walks through the real numbers, the real rules, and the failure modes we’ve seen too many other contractors walk into, because we’d rather you know before you sign than after the first inspection.
Why Barrett & Sons Construction Is Orange’s Preferred Home Additions & ADU Company
Tom Barrett founded this company in 1998, and he’s on-site most days along with his sons, who run the crews. That’s not marketing language. Ask anyone who has watched a Barrett & Sons job in Old Towne or up in the hillside neighborhoods: the name on the truck is the name standing in your driveway. When an Orange homeowner calls, a live person answers, 24/7, every time. Not a voicemail box. Not an out-of-state call center.
We’ve worked in every ZIP code across Orange: 92859, 92862, 92863, and 92864. We know which parcels fall under county permitting and which fall under city review. We know what the Design Review Committee asks for on a second-story addition in Old Towne, because we’ve sat through those meetings. We know that an east-hillside lot near the 92862 ZIP needs a drainage survey before grading, because we’ve had to add French drains and retaining walls that other quotes never mentioned. We carry that local working knowledge into every estimate, so the price we quote is the price that holds.
And when the job is done, you get the 90-Day Done Right Promise in writing on your contract. If something isn’t right, one call brings Tom back. It’s that simple.
Our Home Additions & ADU Services in Orange
New Detached ADU
A new detached ADU in Orange starts with one question: city permit or county permit? On acreage parcels outside city jurisdiction, county health code governs septic and well setbacks, and those setbacks often dictate where the structure can sit. We scope the site, verify setbacks against county records, and position the ADU footprint before we ever quote a foundation price. For hillside lots, we include a pre-construction drainage survey so stormwater doesn’t end up running toward the new footing.
ADU Site Prep & Utilities
Site prep on an Orange acreage parcel costs more than site prep in a tract neighborhood, and it should. We’re running electrical service trenches, water lines, sometimes a new septic feed or a well-line tie-in, and on sloped lots, a retaining wall or re-grade. We pull permits for all of it, and every price change arrives as a written change order before a single scoop of dirt moves.
Second Story Additions
Adding a second story in Orange’s 1950s-1970s ranch neighborhoods is a different job than adding one in Old Towne. In the ranch tracts, we’re working on slab foundations with predictable framing. In Old Towne, second-story work triggers California Historic Building Code requirements on rooflines, exterior trim, and Windows & Doors - Orange placement, reviewed by the Design Review Committee. We factor those costs into the estimate before you sign, not as a change order halfway through.
Garage Conversion ADU
Converting an existing garage into an ADU in Orange can run $30,000-$80,000, depending on whether we’re working with a detached 1940s garage in Old Towne or an attached 1970s garage in the flatter neighborhoods. Old garages often need foundation assessment, new shear walls, and historic-appropriate exterior finishes. Modern attached garages convert faster and cheaper. Either way, we pull the permit, schedule the inspection, and stand behind the work.
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 Orange
We install materials you can look up, not mystery brands off a van. For ADU kitchens and bathrooms we remodel in Orange we use Schluter waterproofing systems, and for bathroom fixtures we regularly specify Grohe and Sterling. On any addition with roofing work, we’re installing GAF. These are brands with published specs and warranties, which matters when an Orange inspector is checking the work and when you’re selling the house later. We stock trim, flashing, and waterproofing materials for Orange jobs in advance, so a mid-project supply run doesn’t stall your schedule.
Common Home Additions & ADU Problems We See in Orange Homes
- Underbidding second-story additions in Old Towne. A contractor who doesn’t know the Historic Building Code quotes standard trim and windows, then hits the owner with a change order that doubles the finish cost when the Design Review Committee requires historically compatible materials. We price compliance from day one.
- Starting a detached ADU without verifying septic and well setbacks. On acreage parcels in the 92862 and 92859 ZIPs, county health code can force the structure 15 feet or more from where the owner assumed it would go. That’s a full re-scope, new permits, and weeks lost. We verify setbacks before the first drawing is finalized.
- Skipping a pre-construction drainage survey on hillside lots. East of the city, stormwater runs downhill. Once you grade, water that used to sheet across the lot can channel toward the new foundation. We had one job off Cannon Street where a French drain and retaining wall were added after the fact on someone else’s project, and it was never in their draw schedule. On our projects, it’s in the original quote.
- Treating every Orange parcel like a standard city lot. Orange has city-permit zones and county-permit zones, sometimes adjacent to each other on the same street. The wrong assumption about jurisdiction can cost you weeks and a re-file fee. We check the parcel status before we quote.
Pricing for Home Additions & ADU in Orange, CA
Here’s what you can expect to budget for the three most common Home Additions & ADU projects in Orange:
| Project Type | Orange Price Range |
|---|---|
| Home Addition | $45,000 - $130,000 |
| ADU Construction | $90,000 - $220,000 |
| Garage Conversion | $30,000 - $80,000 |
What moves the price inside those ranges? A second-story addition in Old Towne lands at the high end because historic review adds material costs, approval time, and compliance work. A detached ADU on flat, city-permitted ground in the 92864 ZIP lands lower than the same ADU on a hillside acreage parcel needing septic relocation, a retaining wall, and a drainage plan. We price all of that in writing, line by line, before you sign. Every allowance is written down. Every change order comes in writing. No surprise invoices at the end. Call (877) 610-1318 for a free estimate, and we’ll walk the site with you.
We Also Serve Cities Near Orange
Our crews regularly work in Villa Park, North Tustin, Tustin, and Anaheim, handling the same range of Home Additions & ADU projects we do in Orange. If you’re just outside the city line and wondering whether we cover your street, call us. If we don’t, we’ll tell you straight, and we’ll point you to someone who does.
Serving Orange, CA - Our Local Coverage Area
We’re based in the Orange 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 Orange
It depends on the parcel’s jurisdiction, and Orange has both. Many acreage parcels in the 92862 and 92859 ZIPs fall under county authority, meaning the county health department reviews septic and well setbacks and the county building department issues the permit. If your parcel is in city jurisdiction, the City of Orange issues the permit. We verify jurisdiction before we quote, because it changes timelines, fees, and what the inspector will ask for. Call (877) 610-1318 and we’ll check your parcel.
Setbacks dictate where the structure can physically sit. If your planned ADU footprint is within 50 to 100 feet of a septic leach field or a potable well, depending on county health code, it has to move. That changes the foundation layout, utility trenching, and sometimes the orientation of the entire build. We verify these setbacks against county records before we draw the site plan. On one hillside lot off Cannon Street, a septic setback pushed the ADU 15 feet farther from the house than the owner expected, which also meant a longer electrical run and a new drainage path. We absorbed that into the re-scope before permits were filed. Call (877) 610-1318 for an exact quote on your lot.
Because Old Towne properties fall under the California Historic Building Code and Design Review Committee approval. Exterior trim, rooflines, window proportions, and sometimes the roof material itself must match the historic character of the original structure. True-divided-light wood windows cost several times what standard vinyl windows cost, and the approval timeline can add weeks before construction even starts. Contractors who don’t work in the district regularly underbid this work, then hand the owner a change order. We price historic compliance in the original estimate. For a written, line-item quote, call (877) 610-1318.
A pre-construction drainage survey, a re-grade plan that directs stormwater away from the new foundation, and if the slope is steep enough, a retaining wall. East-hillside lots in Orange see more intense runoff during Santa Ana rain events, and once you grade, water that used to sheet across the lot can channel toward the new structure. We include a French drain in our punch list when the survey shows water concentrating near the foundation. If your quote doesn’t mention drainage, ask why. Then call (877) 610-1318 for a second opinion, free.
Yes, in Old Towne they do. A detached garage from the 1920s or 1930s sits within the National Register Historic District, and any conversion that changes the exterior, roofline, or window openings goes to the Design Review Committee. Interior conversions face fewer restrictions, but the moment you touch the outside shell, historic review kicks in. That means historically compatible materials, which cost more than modern equivalents. We’ve navigated those reviews on multiple Orange properties and can walk your project through it. For a free estimate on your garage, call (877) 610-1318.
When you’re ready to talk, call (877) 610-1318. We’ll come out, walk the site, and give you a written estimate with every allowance, every permit, and every drainage plan spelled out. Free second opinion on any written estimate you’ve already received, and no trip charge inside Orange County.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Orange since the company’s founding in 1998.