Build Your ADU with Confidence
From cost calculators and city regulations to a complete glossary of construction terms.
Popular Tools
City Cost Guides
Portland
$90K–$380K
Los Angeles
$150K–$350K
San Diego
$200K–$400K
Seattle
$80K–$475K
Scottsdale
$150K–$300K
Sacramento
$200K–$300K
Bay Area
$150K–$475K
Denver
$165K–$340K
Austin
$80K–$360K
Raleigh
$100K–$250K
Miami
$90K–$375K
Houston
$150K–$300K
Dallas
$90K–$235K
Atlanta
$80K–$260K
Charlotte
$95K–$240K
Minneapolis
$85K–$295K
Tampa
$80K–$285K
Resources for ADU Owners
Featured Glossary Terms
ADU Meaning
What is an Accessory Dwelling Unit?
Read MoreJADU Guide
Junior ADU rules, costs & benefits
Read MoreSetback Requirements
How close can you build?
Read MoreGranny Flat
Definition, costs & ADU comparison
Read MoreDetached vs Attached
Costs, pros & cons compared
Read MoreBy-Right Approval
No hearings, 60-day mandate
Read MoreDeed Restrictions
Owner-occupancy & sale rules
Read MoreMinisterial Review
Faster permits explained
Read MoreADU Construction Glossary
Master the language of construction. Use the search below to find definitions for over 200 common ADU terms.
Core Concepts
ADU (Accessory Dwelling Unit)
A secondary housing unit on a single-family residential lot. Often called granny flats, in-law suites, or backyard cottages.
Read full guideJADU (Junior Accessory Dwelling Unit)
A smaller unit (max 500 sq ft) created within the walls of an existing single-family residence.
Read full guideDetached ADU
A stand-alone structure that is physically separate from the primary dwelling.
Read full guideGranny Flat
An informal term for an ADU — a secondary living space originally built for aging family members.
Read full guidePermitting & Zoning
Building Permit
Official authorization issued by a local government agency to allow a construction project to proceed. Look up your local building permit office for specific regional requirements.
Setback
The minimum distance a building or other structure must be set back from a street, road, river, or other boundary.
Read full guideBy-Right Approval
A zoning designation allowing ADU construction without discretionary review, public hearings, or neighbor notification.
Read full guideMinisterial Review
A non-discretionary permit review where applications are evaluated against objective standards only.
Read full guideDeed Restriction
A legal limitation on property use that can affect ADU construction, rental, or sale.
Read full guideLot Coverage
The percentage of a total lot area that is covered by buildings or structures.
Construction Elements
Slab-on-Grade
A type of foundation consisting of a concrete slab poured directly onto the ground.
MEP (Mechanical, Electrical, Plumbing)
The three technical disciplines that encompass the systems that make buildings suitable for habitation.
Load-Bearing Wall
A wall that supports the weight of the floor or roof above it.
Financial Terms
HELOC (Home Equity Line of Credit)
A flexible loan that uses the equity in your home as collateral, often used to fund ADU construction.
Hard Costs
Direct construction costs, including labor and materials.
Soft Costs
Indirect costs such as architectural fees, permits, and engineering reports.
Down Payment (California ADU Contracts)
The payment a builder can ask for before work starts. In California it can't be more than $1,000 or 10% of the contract price, whichever is less (Bus. & Prof. Code § 7159.5).
Read full guideDraw Schedule (Progress Payments)
The list of payments due as each stage of the work is finished. In California, apart from the down payment, a contractor can't collect more than the value of work done or materials delivered (Bus. & Prof. Code § 7159.5).
Read full guideMechanics Lien
A claim recorded against your property by someone who helped improve it and wasn't paid, such as a subcontractor or supplier. CSLB warns it can happen even if you paid your builder in full.
Read full guideLien Release (Waiver and Release)
A signed form in which a contractor, subcontractor, or supplier gives up lien rights for work they've been paid for. California uses four statutory forms (Civil Code §§ 8132–8138).
Read full guideReady to Start Your ADU Project?
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