Convert Interior Space Into a JADU in Redwood City
Up to 500 sq ft inside your existing home, permitted under California AB 881.
What Is a JADU? A Plain-Language Answer for Redwood City Homeowners
A JADU is a small, self-contained apartment built entirely within your existing home.
A JADU — Junior Accessory Dwelling Unit — is a unit of up to 500 sq ft carved from space that already exists inside your primary residence. Think a large bedroom suite, an attached area with its own hallway, or an oversized room with an exterior wall where a door can be added. You're not building outward — you're reconfiguring inward.
California's AB 881 — the state law that governs JADU conversions — sets the rules: maximum size, kitchen requirements, entrance requirements, and the owner-occupancy condition. Most Redwood City homeowners don't realize they already have the right to do this. No variance. No neighborhood vote. If the space and the structure qualify, the law is on your side.
Bark and Build handles JADU conversion projects across Redwood City and San Mateo County — from the initial space review through permitted occupancy.
Licensed by the CSLB under CA #1119304 — active & publicly verifiable.
How AB 881 Changed What's Possible Inside San Mateo County Homes
Before AB 881 passed, converting interior space into a secondary unit was subject to local discretionary review — planning commission timelines and no guarantee of approval. AB 881 established a streamlined, ministerial permit path for JADUs, which means San Mateo County can't deny a qualifying application based on neighborhood character or design preferences. If the plans meet code, the permit has to be issued.
Here's what most homeowners don't realize: the law also allows a junior ADU to share utilities with the main residence. No separate meter is required — a meaningful cost difference compared to a full detached ADU, where utility separation is often required at the connection point.
Redwood City's older housing stock — much of it built between the 1950s and 1980s — often includes bedroom wings, attached in-law suites, and oversized master configurations that map cleanly onto the JADU format. The space is already there; AB 881 gives you the legal path to use it.
When a JADU Makes More Sense Than a Full ADU
Sometimes the right answer isn't building new — it's legalizing what you already have. Some lots are a strong fit for a detached ADU; others are constrained by setbacks, utility access, or existing coverage that leaves little room to build outward. A JADU conversion sidesteps most of those constraints: the unit stays inside the existing building envelope, so detached-structure setbacks don't apply. No new foundation, no roofline extension, no excavation for a utility trench.
We assessed a Redwood City property where the owner wanted to house an aging parent and generate rental income. The lot had under 900 sq ft of rear yard, and the setbacks made a standard detached ADU nearly impossible to size usefully. But the home had a 480-square-foot bedroom suite at the rear — private end of the floor plan, its own bathroom rough-in already in the wall, and an exterior wall facing the backyard.
We designed the JADU around the existing plumbing, added a proper exterior entry door through the exterior wall, and specified an efficiency kitchen with a compact cooktop, sink, and under-counter refrigerator. The permit set went in as a complete package — and came back approved without a correction letter. That's the outcome when the plan is built around the code from the first draft, not revised into compliance after plan check returns with comments.
We Build the Permit Set Around AB 881 From the First Drawing
A JADU conversion has three non-negotiable code requirements under AB 881: a separate entrance directly accessible from the exterior, an efficiency kitchen (compact cooking appliance, sink, and refrigeration), and a unit at or under 500 sq ft. San Mateo County's plan check reviews all three, plus a complete site plan, dimensioned floor plan, and entrance details. A set that's missing a dimension, mislabels an existing wall, or shows a non-compliant kitchen configuration comes back with a correction letter — and correction cycles take weeks.
What makes our approach different is that design and permitting are handled by the same in-house team. Our designers produce the plan set with direct knowledge of what San Mateo County reviewers flag on JADU submissions: the entrance is drawn correctly before submission, the efficiency kitchen is specified to meet habitability standards, and the floor-plan annotations match what reviewers expect.
Every phase of the JADU scope — design through final inspection — is covered under CA License #1119304, active and verifiable on the CSLB website. One submission, not three.
JADU Requirements: Entrance, Kitchen, Size & Occupancy
AB 881 sets four specific requirements every JADU must meet to qualify for a permit — here's what each one means in practice.
From Interior Layout to Permitted Occupancy
Diagnostics
We start with a site review of the interior space: confirming square footage against the 500 sq ft cap, assessing existing plumbing rough-ins for kitchen and bath, evaluating the exterior wall for entrance installation, and checking the separate-entrance requirement. We also cross-reference the parcel against San Mateo County zoning to confirm the property qualifies under current state law.
Implementation
Our in-house team produces the full plan set — site plan, dimensioned floor plan, entrance detail, efficiency kitchen layout, and Title 24 documentation where required — and submits it to San Mateo County. If a correction letter comes back, we respond to it; you don't interpret comments or coordinate professionals. After issuance we handle framing, the separate-entrance door, kitchen rough-in and install, electrical, and finishes.
Final Walk-Through & Close-Out
Before closing the permit, we walk the completed JADU against a checklist aligned to San Mateo County's final inspection: entrance configuration, smoke and CO detector placement, kitchen installation, and any egress window requirements. The goal is a clean final inspection — not a re-inspection cycle.
JADU Conversions Across Redwood City & San Mateo County
Many Peninsula homes built in the 1950s–1970s have oversized bedroom wings, rear suites, or attached spaces that map directly onto JADU eligibility — often a more practical path than new detached construction.
Weighing a full unit instead? Compare our ADU construction page.
Frequently Asked Questions
California law requires the property owner to live in either the primary residence or the JADU itself. You can rent out one unit, but you cannot rent out both simultaneously. This condition runs with the property as long as a JADU exists on the lot.
Yes. Unlike a full ADU, a JADU is not required to have a separate utility meter. Electricity, water, and gas connections can remain shared with the primary residence — one of the primary cost advantages of a JADU over a detached ADU on the same property.
Large bedroom suites, attached in-law areas, rear bedroom wings with exterior wall access, and oversized master configurations are the most common candidates. The space must be within the existing building footprint and cannot exceed 500 sq ft. Homes built in Redwood City between the 1950s and 1980s frequently have room configurations that meet these criteria.
Yes. AB 881 requires the JADU to have its own exterior entry point — either a modified existing opening or a new door installed through the exterior wall. Interior access to the main residence is permitted but does not substitute for the exterior entrance requirement.
A complete, code-compliant JADU submission through San Mateo County's ministerial review typically takes six to ten weeks from submission to issuance, assuming the plan set is complete on first submission. Missing documentation or inconsistent drawings extend that timeline. We prepare the full package in-house to minimize back-and-forth with the building department.
We manage the full scope: initial space review and eligibility confirmation, in-house plan set production, permit submission to San Mateo County, correction letter response if needed, and all construction phases — framing, entrance installation, efficiency kitchen rough-in and finish, electrical work, and final inspection coordination.
Confirm Whether Your Interior Space Qualifies
The fastest way to know if your space works is to have someone look at it. We'll review your interior space, confirm eligibility under AB 881, and tell you exactly what a conversion would involve — before you commit to anything.