The ADU You Already Own Most Of
Every detached ADU starts with the expensive parts: foundation, framing, roof. An interior conversion skips them. If your Van Nuys home has more house than you use — a sprawling rear wing, an oversized bonus room, an attached garage with rooms beside it — that square footage can become a fully self-contained rental unit with its own entrance, kitchen, and bath.
AUTHORITY LINK TODO: adu-interior-conversionCalifornia ADU law goes out of its way to protect conversions of existing space, which is why they're often the smoothest path through LADBS. And unlike a JADU, a conversion ADU is a full ADU: no 500-square-foot ceiling, a real kitchen, and no owner-occupancy string attached for most projects.
The post-war floor plans across Lake Balboa and Valley Glen are full of candidates — long ranch houses whose back thirds live their lives as underused dens.
Conversion ADU vs. JADU: Pick the Right Tool
These two get confused constantly, and the difference decides what you can do with the unit. A junior ADU is capped at 500 square feet inside a single-family home, allows an efficiency kitchen only, and requires the owner to live on site. It's the right tool for a compact in-home suite when you're staying put.
An interior-conversion ADU has no 500-square-foot cap, gets a full kitchen, and — like most standard ADUs — carries no owner-occupancy requirement. Rent it, house family in it, or rent the main house and live in it yourself. If the space you're eyeing is bigger than 500 square feet, or you ever want the whole property tenant-occupied, the conversion ADU is almost always the answer.
We walk both options with the actual floor plan at the estimate, because the right choice falls out of the square footage and your five-year plan — not a brochure.
What the Conversion Actually Involves
Turning interior space into a legal dwelling is real construction hiding inside existing walls. The unit gets separated from the main house with fire-rated assemblies and sound insulation. A full kitchen and bath get plumbed and wired — often the largest single scope, especially where the new kitchen lands far from existing drain lines. Its own exterior entrance goes in, egress windows get sized to code, and heating and cooling arrive via a dedicated system, usually a mini-split.
Behind that, the unglamorous checks that make it legal: panel capacity for a second kitchen and laundry (older 100-amp services usually upgrade), sewer tie-in capacity, insulation brought up to current Title 24 in altered assemblies, and smoke and CO protection throughout. It's the same discipline as our garage conversion builds, applied to living space instead of a parking box.
Permits, Timeline, and the Payoff
Conversion plans move through LADBS under state ADU timelines, and because the footprint already exists, setback and lot-coverage fights mostly don't happen — the walls are where they are. The plan-check attention lands on fire separation, egress, and energy details, which is where we've learned to make drawings airtight the first time.
Construction typically runs faster than a ground-up unit since there's no foundation or framing phase — most conversions finish in a few months once permits are in hand. At the end you hold a certificate of occupancy for a legal, insurable, rentable unit that added a second income stream without touching your yard.
Not sure whether your floor plan has an ADU hiding in it? That's exactly what the free walk-through answers — and if a detached unit or a multifamily ADU package fits your property better, we'll tell you that instead.
Get a free conversion estimate
Tell us about your home and our licensed team will walk the floor plan, confirm what qualifies, and write you a free estimate. CSLB License #1160251. No cost, no obligation.
Van Nuys General Contractor ADU & Remodeling LLC is a licensed California contractor — CSLB License #1160251. We build ADUs, additions and remodels across Van Nuys and the San Fernando Valley, and every project is permitted and inspected through the city.
Frequently Asked Questions
What's the difference between an interior-conversion ADU and a JADU?
Size and rules. A JADU is capped at 500 square feet, must sit inside a single-family home, allows only an efficiency kitchen, and carries an owner-occupancy requirement. An interior-conversion ADU is a full ADU — full kitchen, no 500-square-foot cap, and no owner-occupancy requirement for most ADUs — created from existing space in your home or an accessory structure. Bigger space, fewer strings.
What existing spaces can become a conversion ADU?
Any legally built space you can carve a self-contained unit from: an oversized family-room wing, an attached garage plus adjacent rooms, a rear section of the house with its own access, or an existing accessory structure. The unit needs its own exterior entrance, a full kitchen and bath, and code-level light, ventilation, and ceiling heights — which is exactly what the conversion work creates.
Is a conversion cheaper than building a detached ADU?
Usually, substantially. The foundation, roof, and most of the shell already exist, so your budget goes into systems and finishes instead of structure. The trade-off is that you're giving up part of your existing home rather than adding new square footage — which is the honest first question we talk through at the estimate.
Do conversion ADUs get easier permitting?
They're often the smoothest ADU path through LADBS. State law strongly protects converting existing space — conversions typically face reduced setback issues (the walls are already where they are) and no parking-replacement requirement in most cases. Plans still have to be right the first time: fire separation, egress, and energy details are where conversion plans usually bounce.
Will the ADU need its own utilities?
It needs its own service capacity, though not always separate meters. Most Van Nuys conversions tie into the main house's panel and sewer if capacity checks out; older 100-amp panels often need an upgrade to carry a second kitchen and laundry. We run those checks during design so the utility answer is in the plan, not a mid-build surprise.
Can I rent out an interior-conversion ADU?
Yes — once it passes final inspection and gets its certificate of occupancy, it's a legal rental unit (rentals of 30 days or longer). Unlike a JADU, most conversion ADUs carry no owner-occupancy requirement, so the property can be fully tenant-occupied. That difference alone decides the JADU-versus-ADU question for many Van Nuys investors.