Sub coordination + draw schedule for owner-builder ADUs: a working template
How to sequence the 8-12 subs on an ADU build, where the LADBS inspection gates sit, and a milestone-based payment schedule (deposit / frame pass / rough pass / final / retainage) that keeps leverage with the owner.
A general contractor's biggest hidden skill is sequencing. They know which sub goes first, what has to finish before the next can start, and when LADBS needs to inspect between stages. Owner-builders inherit that scheduling work. Done badly, it adds weeks of mutual sub waiting and racks up no-show fees.
This guide lays out the standard sequence for a detached ADU build, marks where the LADBS inspection gates sit, and presents a milestone-based draw schedule that keeps payment leverage with you until the work is actually done.
The standard ADU sub sequence
A typical 800-1,200 sqft detached ADU touches 8-12 subs across 4-6 months of build time. The order matters because each trade's work depends on the previous trade's completion AND a passing LADBS inspection at the gate.
Phase 1: Site prep and foundation
- Sitework / excavation. Grading, footings, utility trenches. Often the GC's own crew, but owner-builders typically hire a small earthwork sub.
- Foundation sub. Concrete forms, rebar, anchor bolts. Pours the slab or stem walls.
- Underground plumbing. Sewer lateral, water service, gas line stub-out, drain lines through the slab. This work happens BEFORE the foundation pour because some of it gets embedded in the slab.
Inspection gate 1: Pre-pour foundation inspection. Forms, rebar, anchor bolts, and underground plumbing are all inspected together (or close together) before any concrete pours. Failing this gate means tearing out wet concrete; nothing buried can advance.
Phase 2: Frame and dry-in
- Framer. Walls, roof, sheathing, structural ties. Sometimes the same sub as sitework, often a dedicated framer.
- Roofer. Underlayment, flashing, finished roof. After framing inspection.
Inspection gate 2: Frame inspection. Wall framing, roof framing, shear walls, hold-downs all checked. After this passes, the building is "dried-in" and protected from weather.
Phase 3: Rough trades
- C-10 Electrical sub. Service from main panel, ADU subpanel, all branch circuits, light boxes, switch boxes, outlet boxes. No fixtures yet.
- C-36 Plumbing sub. All in-wall plumbing, water lines, drain-waste-vent, gas lines, water heater location prepped.
- C-20 HVAC sub. Ductwork (or mini-split lineset routing), condensate drain, gas line for furnace if applicable.
- C-46 Solar sub. Conduit run from the future panel location to the main panel. Solar PV install often happens later, but the conduit/wire-pull is during rough.
Inspection gate 3: Rough trades inspection. Often called the "rough-in inspection," typically a single combined LADBS visit covering electrical, plumbing, mechanical, and any low-voltage prewiring. Sometimes broken into separate visits depending on inspector workload.
Phase 4: Insulation
- Insulation sub. Walls, ceiling, often a single visit. Air-sealing and weatherstripping happen in this phase.
Inspection gate 4: Insulation inspection. Inspector confirms R-values match Title 24 and there are no compression issues. Once passed, drywall can begin.
Phase 5: Drywall and finish
- Drywall sub. Hang, mud, tape, texture. Usually 2-3 visits across a week.
- Finish carpentry. Trim, baseboards, door/window casing, cabinets. Sometimes the same as framer, sometimes dedicated.
- Tile / flooring sub. Bathroom tile, kitchen tile, floor finish.
- Painter. Prime and finish coats.
- Final electrical / plumbing / HVAC. Fixtures, faucets, light switches, thermostats. The same C-10/C-36/C-20 subs from rough come back for this trim-out.
- C-46 Solar sub. PV panels installed and connected to the panel.
- Appliance install. Range, refrigerator, dishwasher, washer/dryer connected.
Inspection gate 5: Final inspections. A series of separate inspections (final electrical, final plumbing, final mechanical, final solar, final building). Each trade's final must pass before the next can.
Phase 6: Certificate of occupancy
- No new subs. LADBS issues the C of O. LA Bureau of Engineering assigns the permanent ADU address. LADWP finalizes the utility hookups.
Why sequencing matters
A sub who shows up before their predecessor is finished bills you for the wasted trip (typically $200-500). A sub who finishes work that wasn't inspected first may have to tear it out. A sub whose work depends on another sub being done can't bid time accurately, which inflates the project budget.
Common sequencing mistakes:
- Insulation before the rough-trades inspection. You can't bury rough work in insulation before inspection passes.
- Drywall before the insulation inspection. Same problem; drywall covers the insulation before the inspector can check R-values.
- Solar PV install before final electrical. Solar interconnection needs the rest of the electrical system in place.
- Painting before final mechanical. Finish painting after HVAC vents are installed; otherwise you paint over them.
The milestone-based draw schedule
The principle: tie sub payments to inspection passes, not calendar dates or invoice dates. Inspection passes are objective, verifiable, and aligned with project value.
A standard ADU sub contract uses this draw structure:
| Milestone | Payment % | When triggered |
|---|---|---|
| Contract signed / deposit | 10-20% | Sub commits, materials ordered, schedule held |
| Mobilization / materials on site | 10-15% | Materials delivered, work started on site |
| Rough inspection passed (sub-specific) | 30-40% | LADBS inspector signs off on sub's rough work |
| Substantial completion | 20-25% | Sub's work is functionally done |
| Final inspection passed | 10-15% | LADBS final inspection passes for this trade |
| Retainage (held back) | 10% | Released 30-60 days after final passes |
The retainage is the most important line. Withholding the final 10% for 30-60 days after final inspection passes is your only leverage if a sub leaves a punch-list item incomplete, if a defect appears in the first weeks of use, or if a lien claim surfaces from a supplier. Don't release retainage until you have an unconditional final lien release in hand and you've had a chance to use the work.
Concrete example for an electrical sub
For a C-10 electrical sub on a $20,000 ADU electrical scope:
| Milestone | Payment |
|---|---|
| Contract signed | $2,000 |
| Materials on site | $2,000 |
| Rough electrical inspection pass | $7,000 |
| Drywall closed, finishes started | $4,000 |
| Final electrical inspection pass | $3,000 |
| Retainage (60-day hold) | $2,000 |
| Total | $20,000 |
Same structure scales for plumbing, HVAC, framing, drywall. Adjust percentages to match the sub's typical work pattern (e.g., a roofer's mobilization is a bigger fraction because the materials cost is high and the work is fast).
What to put in a sub contract
Even owner-builders should use written sub contracts for any sub over $500. Standard clauses:
- Scope of work (specific, line-by-line, with reference to plans by sheet number)
- Total contract price
- Milestone draw schedule (see table above)
- Lien release requirements at each payment (conditional with payment, unconditional after clearance)
- Workers comp certificate of insurance attached, valid for the work period
- License # (CSLB) and proof of liability insurance
- Change-order process (no verbal change orders; written + signed only)
- Termination clause
- Dispute resolution (typically arbitration in CA construction)
Templates are available through the AIA (American Institute of Architects) and the AGC (Associated General Contractors of California). For ADU-scale work, a 2-3 page contract is enough.
Coordinating overlap
Sometimes two subs need to overlap. The C-10 and C-36 subs often run their rough work simultaneously through the same walls. Roofers and framers may overlap on the same day. Coordination tips:
- Daily standup at the trailer. 10-minute morning sync. Each sub reports what they're doing today and what they need from others.
- Shared schedule. Google Sheets or a project-management app (Buildertrend, CoConstruct, JobNimbus) with the next 2 weeks visible to all subs.
- Single point of contact. You're the GC. Subs talk to you, not to each other through informal channels. Reduces miscommunication.
The honest tradeoff
A GC does all this scheduling intuitively after years of experience. As an owner-builder you'll do it from scratch, with one project's worth of learning. Expect to lose 1-3 weeks of total project time to scheduling friction in the first half of the build before you find your rhythm.
That lost time is part of the price of saving GC margin. If your owner-builder savings are $50K on a $300K project, and you lose 3 weeks of holding costs (mortgage interest + ADU rental income forgone), the net savings are smaller than the gross. Plan accordingly.
Sources
- LADBS inspection sequencing: ladbs.org/inspection
- AIA standard sub contract templates: aiacontracts.com
- AGC California construction industry resources: agc-ca.org
Related guides
- Owner-builder declaration in LA: what CSLB §7044 actually requires
- Workers comp for owner-builders in California
- Mechanic's lien releases for owner-builders
If you're at the rough-trades stage and want a wizard that tracks every inspection alongside your sub payments, the PermitPathLA wizard keeps both threads in sync so you don't pay a sub for work that hasn't passed yet.