Success Story: Bay Area ADU Project

Accessory dwelling units (ADUs) should get a new lease on life in 2020 due to a heavy push for affordable housing perfectly timed with state regulation and advancements in construction technology.

2020 is the year of the ADU, especially for the Bay area. The Bay Area faces a severe housing crisis and people believe the ADU housing approach is a fast and creative way to address affordable housing. The number of ADU in California increased by more than 500% as a result of the 2017 law alone. Just in the Santa Clara Country, the number of ADU permit applications has skyrocketed to more than 200+ applications each month.

However, there are still some barriers for house owners to build an ADU. The most obvious one is the extremely high construction cost in the Bay Area. Some homeowners are thinking about using prefab modular as an option, but this approach is not applicable for most of the sites and has its own disadvantages, such as very limited customization and high cost of modification.

TechPrefab’s penalized system is a creative and hybrid approach of conventional stick-built and modular, making the ADU construction affordable and fully customizable. We are offering a turnkey solution, from design to construction, and is able to control the end-to-end cost around $300/sqft in the Bay Area (foundation included).

Our secret sauce is to make ADU construction quicker and less costly in the same way car or smartphone manufacturers save time and money by using assembly lines to make standard products and components. Tech Prefab is also outsourcing the actual manufacturing of building parts to our global manufacturers, the way technology companies often outsource manufacturing.

It is not an idea. TechPrefab has proved the concept with several ADU projects in the Bay Area, and one of them is today’s Hayward project.


A success project stems from a good design. Unlike the modular construction, your ADU is fully customizable using penalized walls. At this design stage, inefficient communication is always the largest soft cost for the client. Powered by BIMPort™ Platform, we created a seamless design communication and coordination environment for the owner and all professionals. Our manufacturer partners also contributed to the design process for free. In this case, we lower the design cost from 10%-12% to 7%, around $10K for the project.


We are not building a mobile home. The foundation work is the same as the conventional construction, so no need to worry about the quality once it passes the city inspections.

One important way we are saving time and money for the Hayward client is to produce building materials parallelly with the foundation. Once the foundation is done, all building materials are ready to ship to the site.


By moving labor upstream and offsite, fewer workers are required as compared with traditionally built structures. Also, under the plant environment, our ADU client is having more control over the quality and schedule.


To be surprised, ocean shipping is actually much cheaper than land transportation. In terms of time, it just takes 18-20 days from our Chinese Manufacturers to the site. For this Hayward project, the foundation has passed the city inspection and all building materials are on the way to the US. We are expecting to begin the onsite assembly in the next 2-3 weeks. Keep tuned.

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