Junior ADU & Interior Conversion Stopped Working
When a junior ADU or interior conversion “stops working,” it almost always means one of three things: a permitted system inside the unit has failed (electrical, plumbing, or HVAC), the conversion was never finished to the permitted drawings in the first place, or a structural or weatherproofing detail that was deferred is now causing visible damage. Any of these can make the space genuinely unlivable. The good news is that a design-build assessment – drawings in hand, permit history pulled – tells you exactly which category you’re in within a single site visit.
An interior conversion is different from a new detached ADU in one important way: it shares walls, a roof, and often utilities with the main house. That means a failure in one system can look like a failure in another. A bathroom that won’t drain properly might trace back to a venting detail that was never permitted correctly. A room that won’t hold temperature might be a framing air-seal issue, not an HVAC issue. Getting the diagnosis right before ordering parts or calling subcontractors separately is the part that saves money later.
Why It Happens
The Permitted Drawings and the Finished Unit Don’t Match
This is the most common root cause we find on interior conversion call-backs. The permit was pulled for one configuration – a specific wall location, a specific electrical panel circuit, a specific egress window – and somewhere during construction, a change was made without a revision permit. The unit works until it doesn’t, because the system that failed was never built the way the engineer designed it. You can spot this category if you have the original permit set: pull it from your local building department and walk the unit. Walls in the wrong place, missing outlets on a circuit that the drawings show, or an egress window that doesn’t match the spec are all tells.
A Shared Utility Was Tapped Incorrectly
Junior ADUs – what California’s code calls a JADU, though similar configurations exist under different names in other jurisdictions – are typically served by the main home’s water heater, electrical panel, and in some cases gas line. If the conversion was done by a contractor who split these systems informally rather than permitted, you may be seeing the upstream system struggle under added load. Signs: breakers tripping on the main panel that didn’t trip before the conversion, hot water pressure dropping when both units are running, or gas appliances in the ADU with a soft flame.
Weatherproofing or Moisture Has Worked Its Way In
Interior conversions – especially garage-to-JADU conversions – often involve a concrete slab floor and a wall that previously vented to outside. If the vapor barrier under the slab was skipped or the wall assembly wasn’t detailed for conditioned space, moisture shows up as a musty smell first, then efflorescence on the slab, then drywall damage at the base of walls. You’ll usually notice this in spring or after a heavy rain event. It’s not dramatic until it is, and the remediation gets more expensive the longer the framing stays damp.
The HVAC System Is Undersized, Improperly Vented, or Both
A junior ADU or interior conversion that can’t hold a set temperature in either direction – too hot in summer, too cold in winter – is often a duct layout or equipment sizing problem. Conversions that reuse an existing HVAC system without a load calculation for the new conditioned space frequently end up with a unit that runs constantly and still doesn’t hit setpoint. You’ll know this is the category if the thermostat is set correctly, the unit is running, and the room still isn’t within a few degrees of the target after an hour.
What to Do Right Now
- Stop using the system that has failed. If a circuit is tripping, a drain is backing up, or a gas appliance won’t stay lit, stop using that specific system and don’t reset it repeatedly. Repeated resets on a tripping breaker or a failing gas valve can mask a condition that needs a licensed technician – not a homeowner – to diagnose safely.
- Photograph everything you can see. Take dated photos of the symptom – the wet floor, the drywall damage, the stuck window, the non-working outlet. These become part of the documented record that your Ellery assessment will reference. You want before photos that you took, not just a technician’s after photos.
- Pull your permit history if you have access. Most jurisdictions post permit records online. Search for the address and pull the permit number, the inspection record, and the approved drawings if available. Knowing whether the conversion passed final inspection – or whether a final was never called for – changes the diagnosis entirely.
- Do not open an electrical panel, disturb a gas line connection, or attempt to re-vent an HVAC system yourself. These components carry real risk of shock, combustion, or carbon monoxide exposure. Describe what you see and stop there. A licensed technician working from the permitted drawings is the right next step, not a DIY fix on a system you didn’t design.
- Write down the timeline. When did the problem start? Did anything change before it started – a new appliance, a heavy rain, a repair in the main house? A clear timeline helps the assessment technician separate a new failure from a condition that’s been building since the conversion was finished.
How We Fix It
When your local Ellery ADU Studio team arrives, the first thing they do is pull the permit record and compare it to the finished unit. That document-first step is what separates a design-build assessment from a trade contractor showing up with a single specialty. If the drawings and the unit don’t match, that gap is the diagnosis – and fixing it means either pulling a revision permit or, in some cases, rebuilding what was done incorrectly.
The two services that cover almost every interior conversion failure are Junior ADU & Interior Conversion and ADU Site Prep & Utilities – the latter when the issue traces to a shared utility connection, a slab moisture problem, or a utility tie-in that was never permitted correctly.
Every assessment produces a written scope and a written price before any work starts – that’s Haven Standard Clause 1, not a sales promise. The 365-Day Done Right Promise applies: if the finished work doesn’t match the permitted drawings, Ellery makes it right. Typical assessment visits take two to three hours. Remediation timelines depend on what the permit record shows, but you’ll know the scope and the price in writing before the crew touches anything. Call (971) 497-2402 to get your written estimate scheduled.
Frequently Asked Questions
It depends on which system failed. An electrical fault, a gas appliance that won’t stay lit, or a carbon monoxide reading from an improperly vented system are situations where you should vacate the unit and call a licensed professional immediately – not tomorrow. A moisture problem or a temperature control failure is uncomfortable and will cause more damage over time, but it’s not an immediate safety evacuation. If there’s any doubt about gas or electrical, treat it as urgent. Call (971) 497-2402 and describe what you’re seeing; the person who answers can help you determine the right response.
Moisture and structural issues get significantly worse if left alone – a damp wall assembly that costs a few thousand dollars to remediate today can cost several times that if the framing rots. Electrical and gas issues don’t get better on their own and carry safety risk. Permitting gaps – an unconverted unit that never passed final inspection – become harder to correct the longer the as-built condition drifts from the approved drawings. The short answer: none of these get cheaper with time. Call (971) 497-2402 to schedule a written assessment before the scope grows.
Your local Ellery ADU Studio team schedules assessments based on current availability in your area, and a live person answers at (971) 497-2402 around the clock – so you’re not leaving a voicemail and waiting. Interior conversion assessments are planned visits, not emergency dispatches; the technician needs the permit record and the drawings to do the job correctly, so a same-day appointment isn’t always the fastest path to a real answer. Call (971) 497-2402 and whoever picks up will tell you the actual next available window, not a vague “as soon as possible.”
No – not without your written approval of a written change. Haven Standard Clause 1 means you receive a flat written price before any work begins. If the assessment uncovers something that changes the scope – a permit gap that requires additional drawings, a utility condition that wasn’t visible until the wall was opened – that becomes a new written scope with a new written price, presented to you before the crew proceeds. There are no door upsells and no “while we’re in here” additions. The price you sign is the price you pay unless you authorize a change in writing first.
Get It Fixed
Call (971) 497-2402 – a live person picks up, any time. Your local Ellery ADU Studio team will pull the permit record, assess what’s there, and give you a written price before anything starts. Book online if you prefer; either way, the estimate is free and the price is in writing.
Written by Nadia Ellery, Principal at Ellery ADU Studio, designing and building ADUs nationwide since 2015.
What Our Customers Say
"Every allowance was itemised at the start, so the finish selections did not turn into a surprise at the end."
- Benedict H."Handled the whole planning process. We went to one hearing and that was it."
- Rowena C."Garage conversion finished on the drawings and close to the schedule. They were honest that the sewer connection was the unknown, and it was."
- Arjun D.