8-Week ADU Builds: The Weekly Schedule We Actually Run

The real 8-week ADU schedule

Langone Site Services completes most ADU builds — from the 384 sq ft Bean to the 981 sq ft Ellas Retreat — in 8 weeks on standard sites with utilities at the property line and permits in hand. Here's the exact weekly breakdown.

Week 1–2: Site prep and foundation

• Mobilize excavation crew and equipment (we own our fleet, no rental delays)
• Clear, strip topsoil, rough grade to plan
• Excavate foundation, prep gravel base
• Install under-slab utilities (water, sewer/septic, electrical conduit)
• Form and pour monolithic slab
• DEP erosion controls installed from day one

Week 3: Framing and roof system

• Pre-cut framing package delivered
• Walls stood and sheathed
• Roof trusses set, decked, and shingled (30-year architectural)
• ZIP wall and roof system tape and seal complete

Week 4: Exterior envelope

• Windows and doors installed (Matthew's Brothers)
• Vinyl siding hung
• Exterior trim complete
• Rough-in for exterior utilities

Week 5: Rough-in trades

• Electrical rough-in
• Plumbing rough-in
• Mini-split HVAC installation (Mitsubishi ductless system)
• Starlink wiring run
• Inspections scheduled and passed

Week 6: Insulation and drywall

• R23 wall and R49 ceiling insulation
• Sheetrock hung, taped, and primed
• First coat of paint on ceilings and walls

Week 7: Finish carpentry and fixtures

• Tongue-and-groove pine ceilings installed
• LVP flooring throughout
• Cabinets set, granite counters installed
• Delta plumbing fixtures installed
• Recessed LED lighting
• Interior doors hung and trimmed

Week 8: Paint, punch list, and handoff

• Final paint coat
• Full punch-list walk with client
• Appliance installation (if included in package)
• Final inspections + certificate of occupancy
• Handoff walkthrough

Why we hit this schedule

We own our site-work equipment, so our excavation timeline doesn't depend on rental availability or a sub's schedule. The specialty trades (plumbing, electrical) are contracted under our prime so we control the critical path. And we communicate weekly — clients get a Friday text with the week's progress + next week's plan.

What shifts the timeline

• Permits delayed. If the town sits on the application, Week 1 can't start.
• Major weather event. Nor'easters in November or May can shift excavation a week.
• Custom design changes. Requested after permits issue, add 1–3 weeks.
• Long utility runs. Properties without utilities at the line add a week of trenching.

Want an 8-week build on your lot? Compare all 7 ADU models, start with instant pricing, or book a free build consult.