Engineered for your exact lot, permitted through the City of Mountain View. Studios to full 3-bedroom homes, designed around the shape of your property and the house already standing on it.
Custom ADUs from $165,000
Our 1,000 sq ft 3-bedroom model — the largest ADU permitted on a Mountain View single-family lot.
Every custom ADU in Mountain View is governed by size ceilings the city sets on top of state law — and they are tighter than most homeowners expect. Knowing them before anything is drawn is the difference between a permit that clears and a set of plans you pay for twice.
Mountain View allows detached, attached, and junior accessory dwelling units on residential lots, with no minimum lot size. What changes from one property to the next is how much square footage you can put on it, where it can sit, and how tall it can go. Here is the current standard for a single-family property.
| Standard | Mountain View Requirement |
|---|---|
| Maximum size — studio or 1 bedroom | 850 sq ft |
| Maximum size — 2 bedrooms or more | 1,000 sq ft |
| Attached unit | Cannot exceed 50% of the primary home's floor area |
| Side and rear setbacks | 4 feet minimum |
| Maximum height | 28 feet, 1 or 2 stories — a basement counts as a story |
| Parking — no bedrooms | None required |
| Parking — 1 or more bedrooms | One space, with waivers available under City Code 36.12.95 |
| Minimum lot area | No minimum |
| Junior ADU (JADU) | 500 sq ft maximum, entirely within the walls of the existing home |
| Planning permit | Not required — building permit only |
Source: City of Mountain View — Accessory Dwelling Units. Standards are current as of this writing and set by the City; we confirm what applies to your parcel before design begins.
The one that catches peopleA detached ADU up to 1,200 sq ft is only permitted on lots with an existing multi-family dwelling. On a standard Mountain View single-family lot, 1,000 sq ft is the ceiling — and only if the unit has two or more bedrooms. A 1,000 sq ft studio is not permitted. A 1,000 sq ft three-bedroom is.
This is where an ADU builder who works in Mountain View regularly saves you real money. Setbacks, height, and floor area interact with your lot's shape, its slope, and the house already standing on it — and a design that ignores any one of them gets rejected at plan check. We run the zoning review and the setback evaluation before anything is drawn, so the first set of plans submitted is the set built to be approved.
Every custom ADU model we build comes in two exterior styles with the identical floor plan inside. Which one belongs on your property usually comes down to your existing home — a Mountain View Eichler and a 1940s bungalow call for very different treatments, and the ADU should read as part of the property rather than something dropped behind it.
Modern Farmhouse
Pitched rooflines, board siding, warmer detailing
Modern Contemporary
Clean lines, flat planes, larger glazing
We walk your lot, confirm what the City of Mountain View allows on it, and tell you honestly which models fit before you spend a dollar on design. Book a free consultation or see our full design-build services.
Six floor plans, each one a starting point we customize to your lot. Every model comes in Modern or Farmhouse. Every price below is a real starting number — not a teaser rate that climbs once you are committed.
Studio · 1 Bath
$165,000
Starting from
Our most efficient unit, and the fastest route to rental income on a tight Mountain View lot. Well under the 850 sq ft studio ceiling.
Floor Plan & Details
1 Bed · 1 Bath
$235,000
Starting from
A true one-bedroom with French doors to the yard. Deliberately held under 500 sq ft, which keeps it clear of Mountain View's school impact fee threshold.
Floor Plan & Details
2 Bed · 1 Bath
$300,000
Starting from
Two bedrooms without going full size. Stays under 750 sq ft, so it clears the state impact fee exemption while still renting as a two-bedroom.
Floor Plan & Details
2 Bed · 2 Bath
$372,000
Starting from
Two bedrooms, two full baths, one ensuite. Enough room to live in long term rather than pass through. A favorite for multigenerational households.
Floor Plan & Details
3 Bed · 2 Bath
$450,000
Starting from
The largest ADU permitted on a Mountain View single-family lot, and it qualifies because it has three bedrooms. This one lives like a house, not an add-on.
Floor Plan & Details
3 Bed · 2 Bath
$540,000
Starting from
Our largest model, with a primary suite and private patio. In Mountain View this size is permitted on lots with an existing multi-family dwelling, not on standard single-family parcels.
Floor Plan & DetailsWant a size that is not on this list? We draw it custom. These plans exist because they cover what most Mountain View lots need, not because they are the only thing we build. For the full regional picture, see our ADU builder Bay Area page and the complete ADU cost breakdown.
Straight talk on pricing. Our starting-from numbers cover far more than the build itself — and everything outside them is named here, before you sign, rather than discovered in month four.
Covered by the number you were quoted
Named up front, never a surprise
You are never on your own for finishesThrough our showroom partners across the Bay Area, we help you select every finish material — flooring, cabinets, countertops, tile, and fixtures — and have it delivered directly to your project on our construction schedule. All the choice, none of the logistics.
Every item above is broken out in a line-item proposal before you sign anything. You will know exactly what you are paying for and where it goes — in writing, before a single wall goes up.
Most Mountain View homeowners financing an ADU hit the same wall: a standard home equity loan lends against what your property is worth today, not what it will be worth with a second permitted dwelling on it. That gap is what stops good projects before they start.
We partner with RenoFi, which lends against your home's after-renovation value — so your borrowing power reflects the finished property, not the current one. It works across everything we build, from a Mountain View kitchen remodel to a bathroom remodel to a full whole home remodel or custom ADU.
Check If You QualifyBuilding more than one space? See our kitchen remodel, bathroom remodel and whole home remodeling pages for Mountain View, or browse the full range of design-build services.
Permit fees go directly to the City of Mountain View. We never mark them up and we never take a cut. Most builders quote you a vague range for the whole Bay Area — here are the City's own published figures for Mountain View.
If your project requires a new or upgraded utility connection, or any work in the public right-of-way — the sidewalk, the driveway approach — Mountain View charges an excavation permit fee of up to $12,000 on top of the building permit. It applies to new construction, conversions, and JADUs alike. This is the single most common reason an ADU budget moves after the homeowner thought it was settled, and it is the first thing we check when we walk your lot.
State law exempts ADUs under 750 square feet from city impact fees. School impact fees are different, and Mountain View applies them to any new residential square footage over 500 square feet. They are paid directly to the school district, not the city, and Mountain View requires proof of payment before it will issue your building permit.
In practice that means our 499 sq ft one-bedroom clears the threshold entirely, while the 650 and 800 sq ft models owe school fees even though the 650 sits under the state exemption. If you are weighing one size against another, this belongs in the conversation before you decide — not after.
Source: City of Mountain View — Accessory Dwelling Units. Fee ranges are published by the City and are based on construction valuation, so the number for your project depends on scope, size, and site conditions. School impact fees are set by the school district, not the City.
Add it up honestly. A new construction ADU in Mountain View carries roughly $7,000 to $13,000 in building permit fees, plus school impact fees if the unit exceeds 500 sq ft, plus up to $12,000 in excavation permits if your utilities require right-of-way work. That is a real spread, and it is why we never fold permits into a headline price — you would have no way to tell what you were actually paying for.
What we do instead is pull the current fee schedule for your specific address during the free consultation, so the number in your proposal is the number the City will actually charge. For how Mountain View fees compare to the rest of the region, see our ADU builder Bay Area page and the Bay Area ADU cost guide.
This is the whole reason most Mountain View homeowners build. An ADU is not extra space — it is an income-producing asset on land you already own, in one of the strongest rental markets in the country.
These are planning ranges, not guarantees. A detached ADU typically rents below a comparable Mountain View apartment — no gym, no pool, no parking structure, and a shared lot — while still commanding a premium over most of the South Bay because of where it sits. Actual rent depends on your unit size, finish level, parking, privacy, and the block you are on. We pull live comps for your specific address during the consultation.
Read that honestly. That figure is gross yield on the build cost alone. It does not account for permit fees, financing costs, property tax reassessment on the new square footage, vacancy, or maintenance — all of which are real. Net returns land meaningfully lower. What the number does show is the scale: roughly $44,000 a year against land you already own, which is why an ADU competes with almost any other use of the same capital.
A legal, inspected ADU adds documented living area to your property. That is square footage an appraiser counts and a buyer pays for. Unpermitted work does the opposite — it can block a sale outright.
Monthly rent while you hold it, and a higher number when you sell it. Most improvements give you one or the other. An ADU is among the few that reliably gives you both in a market like Mountain View.
Not every homeowner builds for a tenant. Plenty of the ADUs we build in Mountain View house a parent who wants to stay close, or an adult child priced out of the local market. The financial case still holds — you are housing family at zero rent instead of paying Mountain View rates elsewhere, and the property value is there either way.
Every model we build is delivered turnkey: design, engineering, permits, construction, and a professional final clean, handed over ready to occupy or list. You are not left coordinating a punch list between four trades to get a certificate of occupancy.
For Investors & Real Estate Professionals
Plenty of the Mountain View ADUs we build are investments first. If you are buying a property and need to know what it will actually support before you close, or planning more than one build, we handle that differently than a single-family project — lot feasibility reviewed before you commit, written scope and cost you can put in front of a lender, and turnkey delivery ready to rent on handover.
Agents working a client through the same question are welcome to call us in early. A real answer on what a lot allows is worth more to your buyer than a guess.
Most builders quote you the number that sounds best. Here is the number the City of Mountain View publishes, and the reason it is different from what you have probably been told.
California law requires a city to review a complete ADU application within 60 days. That is real, and it is where the 40 to 60 day figure on most contractor websites comes from. It is also not the number that matters.
Sixty days is the clock on one review cycle. Mountain View's initial review runs two weeks. If anything comes back incomplete or non-compliant, you revise, resubmit, and wait another two weeks — and every additional cycle after that is two weeks again. The City's own published figure for the typical time to actually receive an ADU permit is four to six months.
We publish the four to six months because that is what a Mountain View homeowner should budget around. A builder quoting you sixty days is either quoting the statute or has not pulled a permit in this city.
3D design, full blueprints and elevations, Title 24 energy calculations, structural engineering, property survey, and setback evaluation against your specific parcel. We also review preliminary plans with Mountain View's Planning Division before the detailed set is drawn — the City encourages it, and it is the cheapest way to catch a zoning problem.
Submitted through Mountain View's online permit portal. Initial review takes two weeks, then the City returns comments. Each resubmittal cycle is another two weeks. This is where projects gain or lose months, and it is the part we are paid to get right the first time. No Planning permit is required for an ADU in Mountain View — building permit only.
Privacy fencing, portable restroom, dumpster, and a walk of the property with you first to see what landscaping is worth saving. Any excavation permit for utility work in the right-of-way is pulled in tandem with the building permit, not after.
Foundation through finishes, with a City Building Inspector signing off at every stage. If your project requires fire sprinklers or a Public Works permit, those inspections are run separately by each department. Your dedicated project manager coordinates all of it.
The building permit is finaled and occupancy granted once construction is complete and the City's final inspection passes. We bring in a professional crew for a full clean inside and out, then walk the finished ADU with you. Turnkey — ready to move into or list.
From first consultation to keys, for a new construction ADU in Mountain View. A conversion of existing space runs shorter. We give you a schedule built on these numbers during your consultation, not an optimistic one designed to win the job.
Permit timeline and review cycle figures published by the City of Mountain View. The 60-day statutory review requirement is set in California Government Code §66317, which replaced the former §65852.2. Actual timelines vary with project scope, site conditions, and how many review cycles an application requires.
The variable you control is the number of review cycles. A plan set that goes in complete, code-compliant, and correctly dimensioned against Mountain View's setback and floor area rules can clear in one or two. A set drawn by someone unfamiliar with this city routinely takes four or five — which is two extra months, sometimes three, entirely self-inflicted.
That is why the setback evaluation and the Planning Division review happen before we draw anything, and why our architect and engineer visit your site in person rather than working from a satellite image. Getting through plan check quickly is not luck. It is the whole job. Every city runs a different process, which is why our ADU builder in San Jose page publishes an entirely different set of numbers. See the full ADU process across the Bay Area, or our design-build services.
Prefab is a real option and it suits some properties. It does not suit most Mountain View lots, and the reasons are specific rather than a matter of taste. Here is the honest comparison.
| Prefab / Modular ADU | Custom Built On-Site | |
|---|---|---|
| How it is made | Built in a factory to a fixed catalog plan, trucked in, and craned onto a prepared foundation | Designed for your parcel, then framed and finished on your property by one team |
| Fitting your lot | The plan is fixed. Your lot has to accommodate the unit, including crane access and a clear delivery path | The design responds to your setbacks, slope, mature trees, and where your existing home sits |
| Matching your house | Limited exterior options within the manufacturer's catalog | Modern or Farmhouse elevations, finishes chosen to read as part of the property |
| Mountain View size limits | You choose from what the factory offers and hope a size fits under 850 or 1,000 sq ft | Drawn to the ceiling that applies to your unit — using the square footage rather than leaving it on the table |
| Site work | Foundation, utilities, grading, and permits are usually yours to arrange separately | Design, engineering, permits, site work, and construction under one contract |
| Crane and access | Needs street width, overhead clearance, and staging room. Many Mountain View lots cannot take delivery | No crane, no delivery constraint. Materials come in through the side yard |
| Changes mid-project | Effectively locked once the unit is in production | Possible, priced in writing before we proceed, with the cost in days and dollars stated up front |
| Who is accountable | Manufacturer, site contractor, and permit expediter are often three separate parties | One licensed general contractor, one project manager, one point of accountability |
| Where it is faster | Factory build runs parallel to site prep, which can compress the construction window | Plan check is the real bottleneck in Mountain View, and a complete first submittal saves more time than a factory ever will |
On a flat, wide, easily accessed lot where the homeowner wants a standard studio and does not care whether it matches the main house, prefab can be quicker and occasionally cheaper. If that describes your property and your goals, it is a reasonable choice and we will tell you so. What we will not do is pretend a factory unit solves the part of a Mountain View ADU that actually takes time — getting through the City's plan check.
The size ceilings are tight. Mountain View caps a studio or one-bedroom at 850 sq ft and anything with two or more bedrooms at 1,000. A catalog unit that comes in at 900 sq ft as a one-bedroom is not buildable here. A custom plan is drawn to the limit that applies to your configuration, which means you use the square footage you are entitled to instead of losing 150 feet to a factory's standard sizing.
The lots are older and tighter. Much of Mountain View's single-family housing stock sits on parcels with mature trees, narrow side yards, and existing structures placed decades before anyone was thinking about a second dwelling. Four-foot setbacks leave very little room for error, and crane access is genuinely not available on a lot of these properties.
The homes have character worth matching. An Eichler, a postwar ranch, and a 1920s bungalow each call for a different treatment. An ADU that reads as a shipping container behind a period home costs you at resale, whatever it saved you at purchase. See how we handle that in our Mountain View kitchen and bathroom work as well.
We build custom because on the lots we actually work — in Mountain View, across the Peninsula, and throughout the South Bay — it produces a better result for close to the same money. Every one of our six ADU models is a starting point rather than a fixed product, and every one gets adjusted to the property it is going on.
A boutique, owner-led design-build firm. You work directly with the people responsible for your ADU, from the first walk of your lot to the day we hand you the keys.
You deal directly with the owners — the same people from your first conversation to your final walkthrough. No handoff to a crew you have never met, no salesperson who disappears once the contract is signed.
One point of contact who knows your project inside out, from first sketch to final punch list. No call centers, no getting bounced between a scheduler and a foreman, no explaining your job to a stranger every time you call.
Architect, engineer, permit submittal, and construction all in-house. When something needs solving there is nobody to point at — and nobody charging you twice for a redesign that came back over budget.
We design and build on your lot, around your existing home. Every model is a starting point adjusted to your parcel, your setbacks, and Mountain View's size limits — not a factory box dropped in the yard.
Mountain View's fee schedule, its two-week review cycles, its 850 and 1,000 sq ft ceilings, its school impact fee threshold. The reason those numbers are published on this page is that we work with them.
A detailed proposal before you sign anything, with every item priced. The only thing that moves the number is a change you request or something genuinely unexpected behind a wall — and either way you get a written change order first.
Your payment schedule follows completed construction, not our cash flow. California law caps what a contractor can collect before work begins and we follow it. Any builder asking for a large percentage up front is telling you something.
Professional clean inside and out, final City inspection passed, occupancy granted, then we walk the finished ADU with you. You get keys to a completed home — not a punch list to chase across four trades.
Real reviews from Bay Area homeowners, pulled live. Read them yourself rather than taking a number on a contractor's website at face value.
A fully licensed California general contractor. We are happy to provide our license and insurance documentation before you sign anything, and frankly you should ask that of every contractor you are considering. An ADU is permanent construction on your property — the paperwork matters as much as the craftsmanship.
See the work rather than the claims. Our completed projects include ADUs, kitchens, bathrooms, and whole-home renovations across the South Bay and Peninsula, and our homeowner testimonials come from the people who lived through the build. If you want to know who you would actually be working with, start with our story.
The questions Mountain View homeowners actually ask us, answered with the City's real numbers rather than a range that covers the whole Bay Area.
Our custom ADU models in Mountain View start at $165,000 for a 350 sq ft studio and run to $450,000 for a 1,000 sq ft three-bedroom, which is the largest unit permitted on a single-family lot here. A 650 sq ft two-bedroom starts at $300,000 and an 800 sq ft two-bedroom at $372,000.
City permit fees are separate and paid directly to Mountain View. The City publishes $7,000 to $13,000 in building permit fees for a new construction ADU, $3,000 to $5,000 for converting existing space, and $4,000 to $6,000 for a JADU. If your project needs new utility connections or work in the public right-of-way, add an excavation permit of up to $12,000. School impact fees apply to any new square footage over 500 sq ft and are paid to the school district.
Every price includes design, blueprints, Title 24, structural engineering, property survey, setback evaluation, and utility trenching to 20 feet. Finish materials, appliances, and site-specific work are priced separately and broken out line by line before you sign.
The City of Mountain View publishes a typical time to receive an ADU permit of four to six months. Initial plan review takes two weeks, and every resubmittal cycle after that is another two weeks.
You will see other builders quote 40 to 60 days. That figure comes from California law, which requires a city to review a complete application within 60 days. It is the clock on one review cycle, not the total time to permit. Most applications go through several cycles, which is how a 60-day statutory review becomes a four to six month reality.
No Planning permit is required for an ADU in Mountain View — a building permit only. Counting design and engineering up front and construction afterward, a full new-construction ADU runs roughly 11 to 15 months end to end. The variable you control is how many review cycles your plan set needs, which is why we run the zoning and setback review before anything is drawn.
On a single-family property in Mountain View, a studio or one-bedroom ADU is capped at 850 square feet, and a unit with two or more bedrooms is capped at 1,000 square feet. An attached ADU cannot exceed 50% of the primary home's floor area. A Junior ADU is limited to 500 sq ft and must sit entirely within the walls of the existing house.
A detached ADU of up to 1,200 sq ft is permitted only on lots with an existing multi-family dwelling, not on standard single-family parcels.
Other standards that shape what fits: four-foot minimum side and rear setbacks, a 28-foot height limit for one or two stories, and no minimum lot size. Parking is not required for a studio. One space is required for a unit with one or more bedrooms, with waivers available under City Code 36.12.95. You do not need a variance for a compliant ADU. State law requires ministerial review, meaning no public hearing and no subjective design review.
Typical Mountain View ADU rents run roughly $2,200 to $2,500 a month for a studio, $2,600 to $2,900 for a one-bedroom, $3,200 to $3,500 for a two-bedroom, and $3,700 to $4,100 for a three-bedroom.
These are planning ranges rather than guarantees. A detached ADU generally rents below a comparable Mountain View apartment because there is no gym, no pool, no parking structure, and it sits on a shared lot. It still commands a premium over most of the South Bay. Actual rent depends on unit size, finish level, parking, privacy, and the block you are on.
Run the math on a three-bedroom: $450,000 to build, $3,700 a month at the conservative end, roughly $44,400 a year in gross rent. That is a gross yield of about 9.9% on build cost, before permits, financing, property tax reassessment, vacancy, and maintenance.
California Bay Builders & Remodeling is a licensed, owner-led design-build general contractor (CSLB #1130783) building custom ADUs in Mountain View and across the South Bay and Peninsula. Design, structural engineering, permit submittal, and construction are handled in-house by one team, with one dedicated project manager and one point of accountability from your first site walk to final inspection.
What separates us in this city specifically: we build custom rather than prefab, designed around your lot's setbacks, slope, and existing home. We work to Mountain View's actual published fee schedule and review timelines rather than generic Bay Area ranges. And we deliver turnkey, with the final City inspection passed and a professional clean before handover.
The credentials are checkable. Five-star ratings on Houzz and Google, three Best of Houzz Service awards, verified NKBA membership, BBB accredited, and fully licensed, bonded and insured. We provide license and insurance documentation before you sign anything, and you should ask that of every contractor you consider.
Every lot is different, and the best answers come from standing on the property. We will walk your parcel, confirm what the City of Mountain View allows, and give you real numbers before you spend a dollar.
Book a Free ConsultationIf you have the lot, we can build the ADU. Designed around your property, permitted through the City of Mountain View, and delivered turnkey by one owner-led team.
The consultation is free and there is no obligation. We walk your lot, confirm what the City actually allows on your parcel, and tell you honestly what it will cost before you spend a dollar on design.
California Bay Builders & Remodeling
2150 N 1st Street, Suite 400, San Jose, CA 95131
(800) 209-0051 · info@californiabaybuildersandremodeling.com
Licensed, Bonded & Insured · CSLB #1130783
Also Serving Mountain View
Beyond custom ADUs, we handle kitchen remodels and bathroom remodels throughout Mountain View, plus room additions and whole-home renovations across the South Bay and Peninsula. See our full range of design-build services or browse the Bay Area ADU program.
Building accessory dwelling units across Mountain View and the wider Bay Area. If your city has its own ADU page, you can open it below for local permit information, project details, and what to expect.
Do not see your city linked yet? We may still serve your area. Tell us where the property is and we will let you know what your city requires.
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