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ADU remodeling and construction in Mountain View, CA

Have a permitted ADU? Start with a remodel scope. Have a garage? Compare conversion with a new detached ADU before you choose a builder.

Checked against the city's ADU pages on Oct 18, 2026.

Can I build one?
Yes, up to 1,000 sq ft 850 sq ft for a studio or 1 bedroom, 1,000 sq ft with 2 or more. You need a building permit only, no planning permit.[1]
What will the city charge?
$7,000 to $13,000 $7,000 to $13,000 in building permit fees, including inspections. See every fee[1]
Who builds here?
13 licensed builders Each lists Mountain View on its own site and holds an active CSLB license. See the list
See 13 builders Get quotes

Remodel an ADU, convert a garage or build new?

Use these scoping questions before requesting quotes in Mountain View. Your designer and the city need to confirm the permit path for your parcel.

Licensed ADU builders in Mountain View

Ranked by a public score anyone can check: license, years licensed, ADU types and cities shown on their own sites, a local office, and published prices. Nobody pays to move up. Quote requests go to our team with the builder you picked. How we rank

These companies name Mountain View in their service areas. That is not proof of a completed local ADU or experience remodeling an occupied unit. Use the type filters to compare advertised services, then ask for a similar permitted project.

Directory records checked Oct 18, 2026. Use each builder’s service-area and CSLB links below to recheck the records before you hire.

Before you hire a Mountain View ADU builder

  1. 1. Check the license and local project evidence

    Match the contract name and license number to the current CSLB record. Ask for a Mountain View permit number and a reference for your project type. A garage conversion does not establish experience remodeling an occupied ADU.

    Check the contractor on CSLB

  2. 2. Ask what the existing structure needs

    For an ADU remodel or garage conversion, ask the bidder to identify retained walls, foundation repairs, moisture issues and utility upgrades. Put allowances for concealed damage in the quote. Do not assume reusing a building makes it cheaper.

    Compare remodel, conversion and new build

  3. 3. Separate a plan package from work on your lot

    For a detached ADU, compare site-built and prefab bids with the same site work included. Ask who handles access, foundation, trenching, utility connections and permit corrections. Check a claimed preapproved plan against the city’s program.

    See Mountain View’s preapproved plan program

  4. 4. Price the same scope before choosing a builder

    Ask each bidder to separate design, permits, demolition, site work, construction and exclusions. For an occupied ADU, include the work schedule and any temporary move. Compare construction separately from city, school and utility charges.

    Review Mountain View ADU costs and fees

What Mountain View allows

  • Detached ADU, max size[1]

    850 sq ft for a studio or 1 bedroom; 1,000 sq ft with 2+ bedrooms

  • Attached ADU, max size[1]

    Same sizes, and no more than 50% of the main home's floor area

  • Junior ADU (inside the house)[1]

    Up to 500 sq ft, entirely inside the house

  • Height[1]

    28 ft for one or two stories, attached or detached. A basement counts as a story

  • Side and rear setbacks[1]

    4 ft side and rear; front setback follows the zone

  • Units on a single-family lot[2][3]

    1 ADU + 1 JADU, plus a detached new ADU with 4 ft setbacks

  • Parking[1][2][3]

    None with no bedroom. 1 space with 1+ bedrooms (garage, carport or driveway), unless an exemption applies, such as within 1/2 mile of transit, or the ADU replaces an uncovered space

  • Owner must live on site[1][3]

    No for an ADU. City rules require it for a JADU, with a deed restriction; since 2026 state law requires it only when the JADU shares a bathroom
  • The ADU needs its own side-hinged entrance. Detached ADU balconies are capped at 75 sq ft in total, with 10 ft rear and 7 ft side setbacks. Roof decks are not allowed.[1]
  • A site survey is required for any structure within 6 ft of a property line or setback, approved before the foundation pour. A sewer lateral inspection is also required.[1]
  • HCD told the city in May 2026 that its ADU ordinance on file dates from 2023 and may not match current state law.[4]
ADU rules in Mountain View drawn on a typical lot Detached ADU, city standards: up to 1,000 square feet, 4 feet from side and rear lot lines, 28 feet tall. Parking: 1 space if it has a bedroom, with exemptions. Rear lot line Street Main house ADU up to 1,000 sq ft 28 ft tall 4 ft 4 ft Parking: 1 space if it has a bedroom, with exemptions
Detached ADU, city standards. Not to scale.

City fees for an ADU in Mountain View

Fee lines for an ADU in Mountain View
Building permit, new ADU (city's typical range) $7,000 to $13,000[1] Based on a construction valuation of $100,000 to $300,000; includes inspections. Conversions run $3,000 to $5,000 and a JADU $4,000 to $6,000.
Excavation permit, if you need utility or sidewalk work Up to $12,000[1]
Land use document fee 0.24% of construction valuation[5] Collected on all projects at building permit.
Citywide transportation fee $6,273.15 per new single-family unit[5][3] The city's page has no ADU line. State law: no impact fees under 750 sq ft; above that, a share in proportion to the main home.
Park land in-lieu fee Based on land value: $160 to $210 per sq ft of land at low density[5][3] The page does not say how this applies to ADUs. State law bars it under 750 sq ft.
School fees Mountain View Whisman $3.45, Los Altos SD $3.58, MVLA high school $1.72 per sq ft[6][1][7][8][9] For 500 sq ft or more. You pay the districts directly and show the receipt before the permit is issued. MVLA rises to $1.79 on Nov 13, 2026.
Water capacity fee (City of Mountain View) $9,389.06 per single-family detached unit[5][3][1] No ADU line. State law limits capacity charges to a share based on the ADU's size or plumbing fixtures. Conversions that fix a code or zoning problem pay none unless new utility work is needed.
Sewer capacity fee (City of Mountain View) $7,922.69 per single-family detached unit[5][3] No ADU line. The same state proportionality rule applies.
School fee rates for districts in Mountain View (3)

You pay one elementary district (Mountain View Whisman or Los Altos) and the high school district (MVLA).[6]

  • Mountain View Whisman School District[7]Applies at 500 sq ft or more. $3.45/sq ft
  • Los Altos School District[8][10] $3.58/sq ft
  • Mountain View-Los Altos Union High School District[9] $1.72/sq ft
Total cost in Mountain View, fees plus building

How the permit works

  1. 1

    Review your design with Planning

    The city encourages a preliminary review before detailed plans: 650-903-6306 or planning.division@mountainview.gov.[1]

  2. 2

    Submit online

    Upload one PDF plan set with the Green Building worksheet, structural and energy calculations, and a title report or grant deed.[1]

  3. 3

    Pay the fee after prescreen

    Staff send the fee amount after prescreen. Review starts once you pay.[1]

  4. 4

    Plan review in 2-week rounds

    Each review of your plans or resubmittal takes 2 weeks. Pay school fees before the permit is issued.[1][6]

  5. 5

    Build and pass inspections

    Your contractor schedules inspections online. Final inspection grants occupancy.[1]

Review time: 2 weeks for each review round. The typical time to get a permit is 4 to 6 months.[1]

State deadline: State law gives the city 15 business days to say if your application is complete and 60 days to approve or deny a complete one.[3]

Apply at: ePermitsMV

Preapproved plans

Preapproved detached designs get a permit in about 30 days, with 7-business-day reviews, compared with 60 to 90 days for a standard ADU. Typical permit fees are the same $7,000 to $13,000.[11]

Who qualifies: New detached ADUs on single-family or multifamily lots. Only site, zoning and utility details are reviewed.

  • Mountain View ADU Plans Gallery Designs listed on the city's ADU Accelerator site

We could not read the designer list on the gallery site. You buy plans from the designer.

Common questions

How big can an ADU be in Mountain View?

850 sq ft for a studio or 1 bedroom and 1,000 sq ft with 2 or more bedrooms. An attached ADU also can't exceed 50% of the main home. A junior ADU is up to 500 sq ft.[1]

Do I need parking for an ADU in Mountain View?

Not for a studio. With 1 or more bedrooms you need 1 space, which can be in the driveway, unless an exemption applies, such as being within 1/2 mile of transit.[1][3]

How much are ADU permit fees in Mountain View?

The city says building permit fees for a new ADU typically run $7,000 to $13,000. An excavation permit can add up to $12,000, and school fees apply at 500 sq ft or more.[1]

How long does an ADU permit take in Mountain View?

Typically 4 to 6 months, in 2-week review rounds. A preapproved design takes about 30 days.[1][11]

How tall can an ADU be in Mountain View?

28 ft for a one- or two-story ADU. A basement counts as a story.[1]

Nearby cities

What we couldn't confirm

  • The building valuation table in the FY 2026-27 master fee schedule was not read; permit fees use the city's typical range.
  • The city does not say how the transportation, park land and utility capacity fees apply to ADUs over 750 sq ft.
  • Preapproved ADU designer list could not be read.
  • Unit count and parking exemptions come from a third-party mirror of the city code (S76), checked against state law.

Sources

Every fact on this page links to one of these. We read each one on the date shown.

  1. 1. City of Mountain View ADU page: single-family ADU zoning table (850 sq ft studio/1 bedroom, 1,000 sq ft 2+ bedrooms, attached max 50 Checked Oct 18, 2026
  2. 2. GoCodebook (third-party mirror) §§36.12.60-36.12.115 standards Checked Oct 18, 2026
  3. 3. California Department of Housing and Community Development (HCD) All state ADU/JADU rules used in state_baseline.md (sizes, heights, setbacks, parking, owner-occupancy, JADU, Checked Oct 18, 2026
  4. 4. California HCD Ordinance on file from 2023 may be out of compliance Checked Oct 18, 2026
  5. 5. City of Mountain View Development fees effective Aug 22, 2026: water capacity $9,389.06 and sewer capacity $7,922.69 per single-fami Checked Oct 18, 2026
  6. 6. City of Mountain View School impact fees for new construction, conversion or additions of 500 sq ft or more Checked Oct 18, 2026
  7. 7. Mountain View Whisman SD $3.45/sf residential effective July 1, 2024 Checked Oct 18, 2026
  8. 8. Los Altos School District $3.58/sf residential Checked Oct 18, 2026
  9. 9. Mountain View-Los Altos Union HSD MVLA share $1.72/sf Checked Oct 18, 2026
  10. 10. Los Altos School District Adopted Dec 15, 2025 Checked Oct 18, 2026
  11. 11. City of Mountain View Preapproved ADU program: detached new construction Checked Oct 18, 2026