Build your ADU
with the receipts
in hand.
The complete guide to planning, permitting, and building an Accessory Dwelling Unit — plus vetted builders, real cost data, and tools that pencil out your project before you call anyone.
No spam. Independent guidance. We may earn a referral fee when you connect with a builder — it never changes our editorial.
$284k–$382k
Mid-finish detached ADU, moderate site complexity.
- Design + permits
- 11%$36k
- Shell + framing
- 28%$91k
- MEP
- 16%$52k
- Finishes + utilities
- 29%$94k
- Sitework + soft
- 16%$52k
Architect, structural, city fees
Foundation, walls, roof
Electrical, plumbing, HVAC
Cabinets, floors, fixtures
Drainage, landscaping, contingency
The tools
Plan your project before you call a builder.
Each tool runs in your browser, takes under five minutes, and emails the results so you have them when you're ready.
ADU cost calculator
Low/mid/high estimate by state, type, size, and finish level.
Estimate costROI calculator
Cash flow, payback period, and property-value uplift.
See the mathLoan calculator
HELOC, cash-out refi, construction and renovation loans compared.
Compare loansFeasibility check
Seven questions to find out if you can actually build on your lot.
Check feasibilityThe ADU process
Six phases, from idea to occupancy.
Most homeowners spend 9–18 months from first sketch to move-in. Here's what happens and when.
- 012–6 wks
Planning
Test feasibility, set budget, pick a path.
Phase guide - 024–10 wks
Design
Floor plan, elevations, site layout.
Phase guide - 036–16 wks
Permits
Submittal, plan check, revisions.
Phase guide - 044–8 wks
Financing
HELOC, refi, or construction loan close.
Phase guide - 0516–28 wks
Construction
Foundation through final finishes.
Phase guide - 062–4 wks
Inspection
Final, occupancy permit, move-in.
Phase guide
● Typical timeline · 9–18 months end-to-end
See the complete process guideFeatured guides
Start with the questions everyone asks.
PRICE
How much does an ADU cost in 2026?
Breakdowns by state, ADU type, and finish level — with the line items that move the most money.
Read the guideBUILD
Garage conversion ADU guide
The fastest, cheapest path to an ADU — if your garage qualifies. Costs, permits, and pitfalls.
Read the guideCOMPARE
ADU vs. room addition
When an ADU outperforms a traditional addition — and the cases where it doesn't.
Read the guideFor buyers
Looking for a home that
already has an ADU?
We track active listings with permitted ADUs in California and expansion markets — plus the buying-guide essentials (financing, valuation, rent-ability) you need before you make an offer.
The free download
Get the 2026 ADU
Homeowner's Playbook.
A 27-page PDF covering process, costs, permits, financing, and the five most common ways homeowners overspend on an ADU. Plus monthly updates on what's changing in state ADU law.