Junior ADU & Interior Conversion Cost - Design, Permits and Build Under One Contract

How Much Does Junior ADU & Interior Conversion Cost in North Hollywood?

Our Junior ADU & Interior Conversion services in North Hollywood typically cost between $80,000 and $175,000 all-in, drawings through final inspection. That range reflects the actual bids we write for North Hollywood homeowners in 2026 – single-family lots in neighborhoods like Lankershim Flats, Valley Village, and near the NoHo Arts District, where older mid-century homes often have underused attached garages, bonus rooms, or large closeted spaces that convert cleanly into a legal JADU. The number you land on depends heavily on the condition of what’s already there: a finished interior with a functioning subpanel costs far less to convert than a raw storage space with zero plumbing rough-in.

Junior ADU & Interior Conversion Cost Breakdown (2026)

Junior ADUs in North Hollywood cost between $80,000 and $175,000 for a complete design-build project – permit drawings through city sign-off. The table below shows how that total breaks down by category. Every number reflects our written quotes for North Hollywood sites; none are national averages ported in from somewhere else.

The single biggest cost variable is plumbing. If the space being converted sits directly above or adjacent to existing drain lines, adding a bathroom costs $7,000-$12,000. If the drain lines need to be tunneled under a slab to reach the new location – something we see frequently in North Hollywood properties built in the 1950s and 1960s where the original garage slab was poured without any rough-in stubs – that number climbs to $15,000-$22,000 for the plumbing line alone. We document exactly what’s under the slab before we write a final number. That documentation is part of what you receive under Haven Standard Clause 1: a written price before any work begins, based on actual site conditions, not assumptions.

The second biggest variable is the electrical service. North Hollywood has a significant stock of post-war single-family homes with original 100-amp panels that were never upgraded. Adding a JADU to one of these – particularly in the Chandler Estates area or the blocks just south of Burbank Boulevard – almost always triggers a panel upgrade, which adds $4,500-$8,000 to the project before a single nail goes into the conversion itself. We flag this in writing during the estimate, not as a change order at rough-in.

What Affects Junior ADU & Interior Conversion Pricing in North Hollywood

• Starting condition of the space: A finished spare bedroom with existing drywall, a subpanel, and plumbing on an adjacent wall converts for $80,000-$105,000. A raw garage slab with no plumbing, no insulation, and a main-panel-only electrical setup typically runs $130,000-$175,000. The gap between those two numbers is almost entirely labor – not materials.
• Slab and foundation condition: North Hollywood sits in a seismically active zone; the 1994 Northridge earthquake left structural damage in a surprising number of garages and bonus rooms that was never fully addressed. Before we design anything, we assess whether the existing slab is structurally sound and whether any foundation repair is needed. A cracked stem wall or compromised slab edge can add $8,000-$20,000 to a project budget, and it’s better to know that before design than after demolition.
• Plumbing routing and drain location: California JADU law requires a minimum efficiency kitchen and allows (but doesn’t require) a private bathroom. Every foot of new drain line you have to run – especially under an existing slab – adds to the total. We measure and map this in the site assessment.
• LA City fire-separation requirements: LADBS enforces fire-separation between the JADU and the main dwelling – typically a 1-hour rated wall assembly and a solid-core rated door. If the existing wall between a garage and the house is an older drywall partition without proper fire rating, it has to be rebuilt to code. This is a North Hollywood-specific detail that surprises homeowners who got quotes from contractors who skipped the code review.
• Scope of kitchen and bathroom: State law allows a JADU to share the main home’s bathroom, which some homeowners on tighter budgets choose. Skipping the private bathroom drops the project cost by $12,000-$26,000 but also reduces the unit’s rental appeal and resale value. We’ll walk through both options in the written estimate so you can make an informed decision.
• HVAC system choice: North Hollywood’s San Fernando Valley climate is one of the harshest for interior comfort – summer temperatures regularly exceed 100°F, and winter nights occasionally drop below 40°F. A single-zone mini-split handles both directions efficiently. Some conversions try to tap into the main home’s existing HVAC duct system, which is almost always undersized for the added load and creates permit complications. We specify the mini-split by default and include it in the project price.
• Title 24 energy compliance scope: California’s Title 24 applies to JADU conversions. In North Hollywood, where many homes have minimal wall insulation and single-pane windows, the compliance scope can include wall insulation, attic air sealing, new windows, and lighting upgrades. We run the Title 24 calculation before we finalize the design, so the compliance costs are priced in, not discovered at plan check.

How to Save on Junior ADU & Interior Conversion

The most effective cost reduction in a JADU project almost always comes from what’s already in the wall – not from squeezing unit costs out of the contractor. Here’s what we’ve seen work for North Hollywood homeowners.

Start with a space that already has plumbing adjacent. If you’re choosing between converting a room next to an existing bathroom versus a space on the far side of the house, choose the adjacent space. Shaving 20 feet off a drain run saves $4,000-$8,000 in labor and materials, and that’s before you account for slab penetration costs.

Use the shared bathroom option strategically. State JADU law in California explicitly allows the JADU to share the main home’s bathroom – this is not a variance or a special approval, it’s built into the statute. If your tenant will be a family member or a long-term trusted occupant, this option cuts $12,000-$26,000 from the project. If you’re planning to rent to an outside tenant, a private bath is worth the investment.

Don’t cut the permit set to save money. Unpermitted JADUs in North Hollywood cannot be rented legally, are not insurable as rental units, and create title problems when you sell. We’ve seen homeowners pay $40,000-$60,000 to retrofit a permitted compliant JADU after buying a house with an unpermitted conversion. The permit is the asset – the drawings are not optional overhead.

Get a second opinion before you sign. If you have a written estimate from another firm, bring it to us. We offer a free second opinion on any written estimate already in hand – we’ll go line by line and tell you what looks reasonable, what looks light, and what looks like it’s going to show up as a change order later. That review costs you nothing and can save you real money.

Lock your scope before design begins. Scope creep is the most common source of cost overruns in ADU projects. Under Haven Standard Clause 5 (No Surprises), your scope is locked at signing. Adding a second bathroom or upgrading finishes after the permit set is drawn generates real re-work costs – but those are changes you choose to make, not surprises we spring on you.

Time the project with your existing contractor schedule. We’re not going to push artificial urgency – there are no “permit slots” running out. But North Hollywood permit processing through LADBS does take time: plan check for a JADU typically runs 6-12 weeks under standard review. If your timeline matters, starting the design process earlier is worth more than any last-minute cost negotiation.

To get a written project cost for your specific North Hollywood property, call (424) 407-8266. The estimate is free. There is no “call for a quote” runaround – you get a written number, tied to your actual site conditions, before any work is authorized.

FAQs – Junior ADU & Interior Conversion Cost in North Hollywood

What does a Junior ADU cost in North Hollywood in 2026?

A Junior ADU in North Hollywood costs between $80,000 and $175,000 all-in, from permit drawings through final city inspection. The low end applies to spaces that already have adjacent plumbing, a sufficient electrical panel, and finished walls. The high end applies to raw garage conversions that need full plumbing rough-in, a panel upgrade, new insulation, and a new bathroom and kitchen built from scratch. Every estimate Ellery writes includes a line-by-line breakdown, not a single number with a note that says “may vary.” Call (424) 407-8266 for a written estimate on your specific property – no charge.

How much does a garage-to-JADU conversion cost compared to a bedroom conversion in North Hollywood?

A garage-to-JADU conversion in North Hollywood typically runs $120,000-$175,000 because of the work required to bring an unfinished garage shell up to habitable code: insulation, drywall, full plumbing rough-in, a heating and cooling system, egress windows or doors, and the fire-separation assembly between the garage and the main house. A bedroom or bonus-room conversion – where drywall, insulation, and HVAC may already exist – runs $80,000-$120,000, with most of the cost going toward the kitchen rough-in, bathroom addition, and electrical upgrades. The difference between the two is primarily labor hours and plumbing materials, not permit fees or design costs. Call (424) 407-8266 for an estimate tied to your actual space.

What permits are required for a JADU in North Hollywood, CA?

A JADU in North Hollywood requires a building permit through LADBS (Los Angeles Department of Building and Safety), including a full permit drawing set with a site plan, floor plan, electrical plan, plumbing plan, and Title 24 energy compliance report. You do not need a conditional use permit or zoning variance in most North Hollywood single-family zones – AB 68 and subsequent state ADU legislation removed most discretionary approval requirements for JADUs. LADBS plan check for a JADU typically takes 6-12 weeks under standard review, or 4-6 weeks with an expedited over-the-counter submittal if the drawings qualify. Permit fees run approximately $3,500-$7,500 depending on project valuation. Our permit set is the core product – it’s designed for clean plan check, not just for construction guidance. Call (424) 407-8266 for a written project estimate that includes permit fees.

Is a JADU cheaper than a detached ADU in North Hollywood?

Yes – a JADU in North Hollywood typically costs $60,000-$120,000 less than a new detached ADU on the same property. A new detached ADU in North Hollywood runs $225,000-$400,000+ because it requires a separate foundation, new exterior framing, an entirely new utility connection (water, sewer, electrical), and a full set of structural drawings. A JADU uses the existing building envelope, shares the main home’s utility connections, and doesn’t require a new foundation. That said, a JADU is capped at 500 square feet under state law, while a detached ADU can be larger. For homeowners who want a legal rental unit without the cost of a new structure, a JADU is often the right first step. Call (424) 407-8266 to walk through both options with a written price for each.

How long does a Junior ADU conversion take in North Hollywood from start to finish?

A Junior ADU conversion in North Hollywood typically takes 8-14 months from the start of design to final city inspection sign-off. Design and permit drawings take 4-6 weeks. LADBS plan check runs 6-12 weeks under standard review. Construction, once permits are issued, runs 10-16 weeks for most conversions – longer when structural or plumbing work is complex. The most common timeline delays we see in North Hollywood are plan check corrections (usually avoided with a tight permit set) and electrical utility coordination with LADWP, which can add 3-6 weeks to projects that need a new service upgrade. We track the permit status on every project and notify you at each milestone – no wondering where things stand. Call (424) 407-8266 for a project-specific timeline alongside your written cost estimate.

Key Takeaways

• Junior ADU and interior conversions in North Hollywood cost $80,000-$175,000 all-in, drawings through final inspection, in 2026.
• The biggest cost drivers are plumbing routing (especially under existing slabs), electrical panel condition, and whether a private bathroom is included.
• Older North Hollywood homes – particularly those built before 1970 in neighborhoods like Chandler Estates and Lankershim Flats – frequently need panel upgrades and slab plumbing work that adds $12,000-$30,000 to base conversion costs.
• California JADU law caps unit size at 500 sq ft and requires an efficiency kitchen; a private bathroom is allowed but not legally required.
• Unpermitted conversions cannot be legally rented, are not insurable as rental units, and create title problems. The permit is the asset.
• Every Ellery project includes a written price before work starts (Haven Standard Clause 1), a 365-Day Done Right Promise, and a documented photo record.
• A free second opinion is available on any written estimate already in hand – call (424) 407-8266.

Ready to Get a Written Price for Your North Hollywood JADU?

Nadia Ellery and the Ellery ADU Studio team have designed, permitted, and built more than 900 ADUs across the Los Angeles area since 2015 – every one under a single written price that covered drawings and construction together. If you’re weighing a Junior ADU or interior conversion in North Hollywood, the first step is a site assessment and a written estimate, not a ballpark figure over the phone.

We’ll assess your existing space, document what we find, run the Title 24 numbers, and give you a written line-item price tied to your actual property – before any contract is signed. That’s Haven Standard Clause 1, and it applies to every project we take on, including yours.

You can learn more about our full range of design-build services on our home page, or call us directly at (424) 407-8266. A live person answers – no voicemail queue, no callback that doesn’t come. The estimate costs you nothing.

Pricing reflects the North Hollywood market as of 2026. Ellery ADU Studio North Hollywood offers free estimates – call (424) 407-8266.

Written by Nadia Ellery, Owner at Ellery ADU Studio, serving North Hollywood since 2015.