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How Much Does an ADU / Granny Flat Cost in California 2024?


Building an Accessory Dwelling Unit (ADU) in California entails a multifaceted journey, rife with considerations that span design, cost, and contractor selection. As an urban designer specializing in ADUs, I've witnessed the intricacies that often surprise homeowners embarking on this path. Here's a comprehensive guide to demystify the process and avoid pitfalls along the way.




An ADU designed by NPB Design Studio

1. Defining the Scope of Work

Before diving into construction, defining the ADU's specifics is crucial. Location, size, features like jacuzzi or sustainability elements, and future expansion plans impact the overall cost and timeline significantly. Understanding these aspects is vital to crafting a realistic blueprint for your ADU. What type of ADU it is? quantity of bedrooms and bathrooms? Should it be wheelchair accessible? What’s the area and finish level?




A JADU designed by NPB Design Studio

2. Assessing Your Site

Location matters. A flat site might ease construction, but unseen constraints or the availability of contractors and materials nearby could be make-or-break factors. A site visit by professionals like NPB Design Studio can uncover crucial insights that influence the entire project.



Topographic showing the levels in the site

3. Timing Is Everything

A common misstep among my clients is starting contractor interviews before finalizing designs and permits. Each design varies in complexity and cost, leading to different project requirements. Clients often opt for a contractor prematurely based on initial impressions. However, upon obtaining permits, which can take up to a year, they realize cost discrepancies due to market fluctuations, leading to delays and potential scheduling conflicts. This predicament leaves clients with the choice of waiting or finding an alternative contractor to commence the project. Commencing construction prematurely can lead to financial and logistical setbacks. Completing designs and permits before engaging contractors is crucial. Rushing into contractor selection without a comprehensive plan might result in unexpected cost variations and delays.



An ADU designed by NPB Design Studio

4. Choosing the Right Contractor

It's not just about the lowest bid. Prioritize quality, reliability, and references over cost alone. Three key elements—time, money, and quality—demand equilibrium, making a medium-priced contractor who delivers quality within a reasonable timeframe the ideal choice. It is urgent to call the contractors’ references and ask about them.



The kitchen was designed by NPB Design Studio


5. Safeguarding Your Investment

Protect your interests with a robust contract, and insurance, and retain a portion of payment (30%) until project completion. Contractors' priorities might not align with your vision; thus, maintain a vigilant eye on project progress and decision-making. Embarking on an ADU journey necessitates informed decisions and safeguards. A contractor isn't your friend; consulting your architect or designer often remains pivotal. Remember, it's not just building an ADU; it's crafting a legacy that demands meticulous planning and execution.



An ADU designed by NPB Design Studio


While construction costs may be important, One common misconception is that clients believe they must have the entire sum of money up front to commence this ADU journey. However, construction can progress in stages, spanning nearly a year for completion. Don't let financial constraints deter you from initiating the process.


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Urban Design and Drafting Services- San Diego & OC 

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