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 Morgan Hill
Adding square footage to a Morgan Hill home runs anywhere from $45,000 for a modest bump-out to $220,000 for a fully finished detached ADU. Most of our Morgan Hill work falls in the $90,000 to $130,000 range because the hillside parcels and tract-home lots here carry seismic and fire-code requirements that flatlanders don’t have to think about. If you’re planning a room addition, garage conversion, or ADU in Morgan Hill, call us at (877) 610-1318. Tom Barrett and his sons know exactly what the City of Morgan Hill building department will flag before you spend a dollar on plans.
We’re the Home Additions & ADU team that shows up in person, walks your lot, and tells you the truth about what your specific parcel will require. That matters here more than most places.
Why Barrett & Sons Construction Is Morgan Hill’s Preferred Home Additions & ADU Company
We’ve been owner-operated since 1998, and Tom Barrett’s name, address, and license number are published where anyone can look them up. No franchise dispatches strangers to your door. When a crew works on a Morgan Hill addition, Tom or one of his sons is on-site most days. The guy you shake hands with at the estimate is the guy who stands behind the work when it’s done. That’s not marketing. That’s how a family company runs.
Morgan Hill homeowners call us because the permit process here is genuinely unforgiving. The building department sits directly on the Calaveras Fault, and they review plans like it. Soils reports get flagged. Chapter 7A fire assemblies get required on hillside lots. HOAs in the master-planned communities along Cochrane Road and East Main Avenue reject detached ADUs that are visible from the street. We know these rules because we pull permits here every month, not once a year. Every eligible job gets permits pulled and inspections signed. No exceptions, no “you don’t really need one for this.”
Our 90-Day Done Right Promise is written on every contract. If something isn’t right, Tom comes back and makes it right. One call. We also answer our phone with a live person 24/7. Not a voicemail box, not an out-of-state call center.
Our Home Additions & ADU Services in Morgan Hill
Here’s what we handle most often in Morgan Hill, based on the housing stock and lot patterns we see in 95037 and 95038.
ADU Design & Permitting
A detached ADU on a flat 1990s tract lot in Morgan Hill is a different animal than one on a hillside parcel off Cochrane Road near the Diablo Range foothills. The hillside version sits in a CAL FIRE Very High Fire Hazard Severity Zone, which triggers Chapter 7A ignition-resistant construction assemblies. That’s roof sheathing and venting, plus exterior cladding requirements the tract-home version won’t face. We scope both correctly from the first site visit so your permit package doesn’t bounce back twice and cost you weeks. A typical Morgan Hill ADU permit package with soils report, structural calcs, and city submittal runs as part of a $90,000 to $220,000 project, depending on size and site conditions.
Garage Conversion ADU
Converting an attached garage into a Junior ADU is one of the fastest ways to add rentable square footage in Morgan Hill without touching your lot coverage. On a 1990s tract home off Cochrane Road, our crew converted a builder-grade attached garage into a Junior ADU, replacing the original slab-on-grade with an engineered foundation tied to the existing post-tension slab. The scope included a kitchenette rough-in with Kohler fixtures, a Moen shower valve, and Cambria countertops for the refinished bath. We pulled permits through the City of Morgan Hill and cleared inspection sign-off without a single change order. Garage conversions in Morgan Hill typically run $30,000 to $80,000.
New Detached ADU
A standalone ADU in Morgan Hill gives you the most flexibility, but the siting rules are strict. HOA communities near East Main Avenue frequently ban secondary units visible from the street, so placement on the lot matters before you file anything. We handle site prep, utilities, fire-rated separation, and the full structural package. If your parcel is east of 101 toward the Diablo Range, expect the dual seismic-plus-Chapter-7A review to add engineering time. That’s not a surprise cost if it’s scoped in writing before we start. Detached ADUs here run $90,000 to $220,000 depending on square footage, foundation type, and hillside grading.
Junior ADU & Interior Conversion
Junior ADUs in Morgan Hill work well for homes where a formal addition triggers setback or daylight-plane problems. Converting an existing interior space, like a large den or bonus room, into a JADU with its own entrance, kitchenette, and bath keeps the footprint the same. On 2000s homes with active builder warranties, we flag which modifications could void coverage before we touch a wall. That conversation happens at the estimate, in plain English, with the relevant warranty language reviewed. JADU conversions typically range from $45,000 upward within the broader home addition envelope.
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 Morgan Hill
We install materials you can look up, not mystery brands off a van. For Morgan Hill additions and ADUs, we regularly work with Simonton windows and PGT impact-rated exterior doors, plus Ply Gem siding, where hillside fire codes or wind exposure call for them. We order directly from regional supply houses that serve the South County market, so lead times are predictable and warranty claims are handled through established channels. If you’ve already got a brand preference, tell us and we’ll quote it. If you don’t, we’ll explain what lasts on a Morgan Hill hillside versus what’s fine on a flat tract lot.
Common Home Additions & ADU Problems We See in Morgan Hill Homes
- Soils reports skipped on flat lots. A homeowner files for an ADU permit on a 1990s tract lot without a soils report, then has to add piers after the building department flags expansive clay under the proposed footprint. Morgan Hill’s shrink-swell clays are real, and the city checks. Budget for the report up front, not after plan check.
- HOA rejections after site prep starts. An HOA in a 2000s master-planned community near East Main Avenue rejects a detached ADU after the owner starts grading, citing architectural standards that ban secondary units visible from the street. We pull HOA design review feedback before you spend on site work.
- Roof sheathing fails rough-in on hillside parcels. A hillside addition off Cochrane Road gets framed with standard roof sheathing, but the inspector fails the rough-in because the parcel is in a Very High Fire Hazard Severity Zone requiring Chapter 7A-rated assemblies. That replacement cost could have been scoped from day one.
- Builder warranties voided by unpermitted work. A 2000s home with an active builder warranty gets a JADU conversion without permits, and the builder later denies a claim because the unpermitted work touched structural members. Permits protect your warranty position. We pull them on every eligible job.
Pricing for Home Additions & ADU in Morgan Hill, CA
Morgan Hill pricing reflects the cost of doing seismic and fire-code work correctly. You won’t get a discount for skipping it, because the inspector won’t let you occupy the space. Here’s what our Morgan Hill jobs actually cost, in writing:
| Project Type | Morgan Hill Price Range |
|---|---|
| Home Addition | $45,000-$130,000 |
| Garage Conversion ADU | $30,000-$80,000 |
| ADU Construction (detached) | $90,000-$220,000 |
Hillside grading, pier-and-beam foundations on expansive clay, Chapter 7A assemblies, and architectural committee fees all move the number. That’s why we give you a written line-item quote after walking your specific Morgan Hill parcel, not a phone estimate. Call (877) 610-1318 to schedule your free estimate. No trip charge inside the county.
We Also Serve Cities Near Morgan Hill
Our crews cover Morgan Hill plus the surrounding South County communities: San Martin, Gilroy, Communications Hill, and Interlaken. If you’re just over the line in one of those areas, the same Home Additions & ADU in Morgan Hill team can handle your project, and the same written-scope rules apply.
Serving Morgan Hill, CA - Our Local Coverage Area
We’re based in the Morgan Hill 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 Morgan Hill
Yes, in practice. The City of Morgan Hill has flagged expansive clay under multiple flat tract lots in 95037 and 95038, and the building department will not accept a detached ADU foundation design without a geotechnical review. Budget $2,500 to $5,000 for the report and any pier adjustments it triggers. Call (877) 610-1318 for an exact scope on your parcel.
Attached garage conversions are generally easier to get through HOA review than detached units because they don’t change lot coverage or street visibility. But every HOA differs, and some near Cochrane Road restrict exterior changes like added entries or window modifications. We pull the HOA’s architectural standards and review them with you before you pay for plans. Free second opinion on any written estimate.
Your structural engineer has to design for a magnitude-6-class fault, which means stronger shear walls, specific hold-down hardware, and often upgraded connections at the first-floor plate line. You can’t skip this. We scope the seismic package in writing so the engineering cost doesn’t arrive as a surprise line item after plan check. Estimates are free at (877) 610-1318.
Yes, if the parcel sits in a CAL FIRE Very High Fire Hazard Severity Zone. That covers much of the hillside land east toward the Diablo Range and west toward the Santa Cruz Mountains. Chapter 7A affects roof covering, vents, gutters, and exterior wall materials. We build sunrooms with rated assemblies from the first day so you don’t fail rough-in. Call for a written quote.
It can, if the work touches structural members, plumbing, or electrical systems that the original builder still warranties. The safe path is to review the warranty documents before starting and pull permits for everything. We walk you through that review at the estimate. Free estimates at (877) 610-1318.
Contact Barrett & Sons Construction in Morgan Hill
If you’re planning a room addition, garage conversion, or ADU in Morgan Hill, get a written line-item quote from a company that’s been doing this since 1998. Tom Barrett’s name, address, and license number are published and verifiable. Every scope, every allowance, every price change arrives as a written change order before work happens. Permits pulled and inspections signed on every eligible job. Call (877) 610-1318 to schedule your free estimate today.
Written by Tom Barrett, Owner of Barrett & Sons Construction, serving Morgan Hill and the South County area since 1998.