Everything you need to build an ADU in Sunnyvale — lot eligibility, size limits, the 800 sqft streamlined vs. MPP permit tracks, E-OneStop submission guide, and a full cost breakdown. All sourced from official City records and Sunnyvale SMC Chapter 19.78.
Data verified 2026-08-18 · City of Sunnyvale · SMC Chapter 19.78 · CA HCD · CA Gov. Code §66310–66342
Lot Eligibility
ADUs are permitted on most residential lots in Sunnyvale under California state law. Select your ADU type and zone below — results use verified City rules as of 2026-08-18.
Instant eligibility check — Sunnyvale rules as of 2026-08-18
Sunnyvale's 800 sqft Threshold — Know Before You Design
Sunnyvale has a clear two-track permitting system based on the 800 sqft threshold. Choosing the right track upfront saves weeks.
ADUs ≤800 sqft — Streamlined Track
ADUs >800 sqft — Standard Track
ADUs are allowed in R-0, R-1, R-2, R-3 zones and mixed-use zones where residential use is permitted. No minimum lot size. Multi-family properties also qualify under state law.
California removed the owner-occupancy requirement in January 2020 (SB 13). You can build an ADU on a rental or investment property in Sunnyvale. ADUs approved after Jan 1, 2020 cannot be used for short-term rentals (min 30-day rental per AB 976).
ADUs are not permitted in portions of a lot that are within existing easements prohibiting permanent structures — verify easements before design. Contact Sunnyvale Planning at (408) 730-7440 or planning@sunnyvale.ca.gov before finalizing your design to confirm there are no deed restrictions or easements blocking your ADU footprint.
ADU Types & Sizes
Sunnyvale allows four ADU types under SMC Chapter 19.78. State law sets a floor of 800 sqft the city cannot go below. The key local rule: ADUs over 800 sqft require a Miscellaneous Plan Permit before the Building Permit.
| Rule | Sunnyvale | Source |
|---|---|---|
| Min. detached ADU size (state floor) | 800 sqft | CA Gov. Code §66321 |
| Side & rear setback (detached) | 4 ft minimum | CA Gov. Code §66332 |
| Separation from main building | 5 ft wall-to-wall | Sunnyvale SMC §19.78 |
| Streamlined review threshold | ≤800 sqft (Building Permit only) | Sunnyvale ADU Program |
| MPP required for | >800 sqft ADUs | Sunnyvale SMC §19.78 |
| Parking required | None | CA Gov. Code §66333 |
| TIF exemption | ADUs ≤750 sqft | SB 13 / CA Gov. Code §66324 |
| School fee threshold | 500+ sqft living area | Sunnyvale ADU Program |
Permit Process
Permits are submitted online through E-OneStop . Streamlined review (4–6 weeks) applies to ADUs ≤800 sqft — no planning approval needed. ADUs over 800 sqft require an MPP first, adding 2–4 weeks to the timeline.
Sunnyvale's 800 sqft Rule
ADUs ≤800 sqft: Building Permit only — streamlined 4–6 week review, no planning step. ADUs >800 sqft: Miscellaneous Plan Permit (MPP) required first from Planning Division, then Building Permit — total 6–12 weeks. The 60-day state clock applies from complete application submittal.
#1: ADU exceeds 800 sqft — MPP required first
Designing over the 800 sqft streamlined threshold adds a full planning review step (Miscellaneous Plan Permit) before the building permit can be submitted — adding weeks to the timeline.
#2: Utility capacity — water closet count
If the total number of water closets on the property exceeds 5, the building sewer must be upgraded to a 4-inch line. Verify utility capacity early before finalizing plans.
Feasibility & Zone Check
Confirm your zone (R-0, R-1, R-2, R-3), setbacks, lot coverage, and any easements that prohibit permanent structures. Check for HOA deed restrictions. Contact Sunnyvale Planning at (408) 730-7440 or email planning@sunnyvale.ca.gov before finalizing your design.
Choose Streamlined vs. Standard Track
ADUs ≤800 sqft: Building Permit only — fastest path, no planning review. ADUs >800 sqft: Miscellaneous Plan Permit (MPP) required first from the Planning Division, then Building Permit — adds approximately 2–4 weeks to the overall timeline. Staying at or under 800 sqft is the single most impactful design decision you can make for speed.
ADUs over 800 sqft incur the MPP planning review step AND Transportation Impact Fees above 750 sqft. Design to ≤800 sqft (ideally ≤749 sqft) to avoid both.
Design & Engineering
Full permit-ready plan set: architectural drawings, structural calculations, and Title 24 CF1R energy compliance. For streamlined ADUs (≤800 sqft), pre-reviewed designs from Sunnyvale's ADU Plan Gallery may reduce review time — zHeight evaluates whether a gallery plan fits your lot's setbacks and utilities, or whether a custom design is the faster path.
Submit via E-OneStop
Apply online at https://ecityhall.sunnyvale.ca.gov/cd/. Upload your complete plan set digitally — no office visit required. Verify utility capacity before submitting: if total water closets on the property exceed 5, the building sewer must be upgraded to a 4-inch line before permit issuance. In-person help available at the One-Stop Permit Center, One-Stop Permit Center, City Hall, 456 W. Olive Ave, Sunnyvale, CA 94086.
Check water closet count early: more than 5 total on the property triggers a mandatory sewer upgrade to 4-inch line — a cost and schedule item often discovered late.
Plan Review & Corrections
Streamlined (≤800 sqft): 4–6 weeks. Standard (>800 sqft): 6–12 weeks including MPP step. The 60-day state approval clock applies from a complete application submittal (CA Gov. Code §66333). zHeight responds to all City correction letters until your permit is approved.
Permit Issued — Build
Pay permit fees online or at City Hall (One-Stop Permit Center, City Hall, 456 W. Olive Ave, Sunnyvale, CA 94086). Receive your building permit and schedule required inspections — foundation, framing, rough MEP, insulation, and final — through E-OneStop. Contact Building Division at (408) 730-7444 for inspection scheduling questions.
Cost Guide
ADU costs break into three buckets. City permit fees are valuation-based — verify current amounts with the Building Division at (408) 730-7444 before budgeting. Ranges below are Bay Area market estimates.
$7,000 – $16,000+
zHeight flat-fee or custom quote. Includes architectural plans, structural calculations, and Title 24 CF1R. ADUs requiring MPP (>800 sqft) may run higher due to additional planning documentation.
Valuation-based
Fees are valuation-based and set by the City. Impact fees: Transportation Impact Fee exempt for ADUs ≤750 sqft. School district fees apply to new-construction ADUs with 500+ sqft of living area. Call Building at (408) 730-7444 for current fee amounts before budgeting.
$300 – $500+ / sqft
Paid to your licensed general contractor — not zHeight. Detached ADUs typically run $200K–$500K+ total. Garage conversions cost less. Utility upgrades (e.g., sewer upsizing) add cost. Get contractor bids after permit approval.
Verify Permit Fees Before Budgeting
The City of Sunnyvale uses a valuation-based fee schedule. Key thresholds: Transportation Impact Fee exempt for ADUs ≤750 sqft (state law). School district fees apply to new-construction ADUs with 500+ sqft of living area. Incremental sewer and water connection fees are exempt for ADUs. Call Building at (408) 730-7444 or Planning at (408) 730-7440 for current amounts before finalizing your budget.
Want a cost estimate for your specific lot and ADU type?
Get a Free Project EstimateWhy zHeight
Sunnyvale's 800 sqft threshold is the most consequential early decision in your ADU project. Here's exactly what's included in a complete permit package — and why the track choice matters before design begins.
The fastest Sunnyvale ADU is ≤800 sqft. Sunnyvale's ADU Plan Gallery offers pre-reviewed designs that may further reduce review time for streamlined-track ADUs. zHeight evaluates whether a gallery plan fits your lot's setbacks, utilities, and easements — or whether a custom design is the faster, safer path. We handle E-OneStop submission and all City correction responses regardless of which track your ADU is on.
| What you need | DIY / Generic | zHeight Package |
|---|---|---|
| Plan drawings | Generic templates — may not match your lot's setbacks, easements, or utilities | Drawn specifically for your Sunnyvale lot, confirming 800 sqft track and setbacks upfront |
| Streamlined track analysis | You determine whether MPP is required — easy to miss the 800 sqft threshold | zHeight confirms your track (streamlined vs. MPP) before design begins — no surprises |
| Structural engineering | Generic calcs — may not match your soil, foundation, or Sunnyvale requirements | Site-specific structural calcs stamped by a licensed engineer |
| Title 24 CF1R | Not included — required separately before permit is issued | Included in every permit package |
| E-OneStop submission | You submit and monitor the portal yourself | zHeight handles submission and monitors E-OneStop for review status updates |
| Plan check corrections | You respond to City correction letters | zHeight responds to all corrections until permit is issued |
The #1 cause of permit delays is an incomplete plan set at intake. zHeight's organized, City-compliant submission — correct file formats, all required sheets, Title 24 CF1R included — avoids rejection before review even begins.
zHeight provides architectural drawings, structural engineering, Title 24 compliance, and permit processing. We coordinate with your chosen licensed General Contractor throughout — we do not perform construction or contracting.
FAQ
Common questions about ADU eligibility, zoning, setbacks, the E-OneStop portal, the 800 sqft streamlined track, and costs in Sunnyvale.
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Our Services
From a kitchen remodel to a full ADU build, zHeight handles the design, planning, and permitting. We work alongside your contractor — we are not the builder.
Design & permitting only. zHeight provides architectural drawings, structural engineering, Title 24 compliance, and permit processing. We do not provide construction or contracting services. We coordinate with your chosen builder throughout the process.
Detached ADU, attached ADU, JADU, and garage conversion plans — permit-ready and E-OneStop-compliant for Sunnyvale. Streamlined (≤800 sqft) and MPP-track packages available.
Layout changes, kitchen and bath redesigns, wall removals, and structural updates. We draw the plans — you hire the contractor.
New rooms, bedroom additions, second stories, and square footage expansions — fully permitted and code-compliant.
Ground-up home builds and whole-home designs. Full plan set from concept to permit approval.
zHeight — Sunnyvale
We handle the complete permit package — architectural drawings, structural, Title 24 CF1R, E-OneStop submission, and correction response — so your project moves from submission to permit. Streamlined (≤800 sqft) and MPP-track (>800 sqft) packages available.
All regulatory data verified 2026-08-18 against City of Sunnyvale ADU Program, Sunnyvale SMC Chapter 19.78, CA HCD, and CA Gov. Code §66310–66342. Fee amounts should be confirmed with Building Division at (408) 730-7444 before budgeting.