1 年前
As a result of favorable policies, more and more homeowners start to pay attention to ADU projects. How would you plan the initial ADU design as a non-architect? Could you build an ADU on your property? Is Detached ADU or Attached ADU better? We will do a case study for you today and hope it will help the readers in need.

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Project Parameters
Project Location Fremont CA
Project Type Addition + Detached ADU
Lot Size 9,963 sq. ft
Gross Floor Area 2,373 sq. ft
Existing House Area 1,061 sq. ft
Expansion Area 700 sq. ft
ADU Area 712 sq. ft
Cost $192,240 (ADU only, labor and raw materials)
$189,000 (Addition only, labor and raw materials)
Project Cycle
Design 6 Months
Construction 10 Months

Architectural Design Analysis

1. Understand the Owner’s Need

The owner of this project is in the Bay Area, this property is an investment property purchased may years ago. The construction this time is to increase the value of the property and for rent.

2. Property Location Analysis
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This project locates in the heart of Fremont, which is the heart of the East Bay. This location is in a great school district, with convenient transportation, adjacent to the 880 freeway, the economy is growing in the area, and it is surrounded by many businesses. It is one of the most valuable locations in the East Bay. Currently, the long-term rent is around $1,500 – $2,000 on the market. Considering the current labor cost, a comprehensive calculation shows that it is good for ADU. We suggest choosing quality guaranteed but inexpensive finish materials, for faster recovery from the cost.

3. Project Design Analysis

Code Requirements:

  • Land Property: The property of the project land is Single Family House, as low-density residential land. The code allows us to build either detached or attached ADU.
  • Maximum Area: The maximum area of the ADU shall be subject to the requirement that the gross floor area should not exceed FAR, green area ratio, and other architectural codes.
  • Parking: The bus station is within 1/2 mile from the property. A waiver for ADU parking space can be applied.
  • Setback:According to multiple codes, rear yard and side setbacks shall not be less than 5 feet of detached ADU; while the setback for attached ADU shall be satisfied by the requirement for a primary property

Note: This project was designed before 2020. It was subject to 2017 regulation and following advised versions.

Construction Options:

Based on the current situation of this project, there are the following options:
1)Detached ADU + Addition
2) Attached ADU + Addition

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Comparison Between the Two Options:
1)Attached ADU + Addition. It guarantees a relatively large green area in the back yard and keeps the entirety of the house. From the overall layout, it looks more like one house, and it follows more strict codes, for example in the setback.
2)Detached ADU + Addition. It is apparently more suitable for renting. Two independent units are physically completely separated with no interference with each other. But it cuts the backyard space significantly, and it almost makes the green area of the project several small pieces around the two units.

Considering the owner’s ideas, Detached ADU + Addition option was adopted, and the reasons as follow:
As shown in the picture, ADU and the main house are two independent living units, and they have completely realized the space division. Two units have separated water meters and electricity meters. Two independent living units increase the rental value of the house and the addition raises the value of the house again.

4. Site Plan Analysis

Considering the terrain, the addition area can be added to the left, rear and right side of the house, like section 1, 2, and 3 shown in the picture.

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Comparing the advantages and disadvantages to make a summary
Section 1: Considering both the garage and the kitchen are in the left of the house, so, making the addition to the left side of the house requires a big change to the existing house, and the construction cost would increase greatly. Moreover, the left side of the house is too close to the property line, and it does not leave enough space for the addition.
Section 2: To include the Detached ADU in the layout, as much space should be reserved in the backyard as possible. So, to make the addition in section 2 needs a second thought.
Section 3: 3 bedrooms locate the right of the existing house, and the right side is relatively farther from the property line. It is a more suitable plan and adds a larger area.

Therefore, considering the functional zoning and the constructional cost, the combination of 2 and 3 is the ideal plan. As shown in the picture below:

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Site plan

5. Architectural Details
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Floor plan

The ADU has a 2b2b layout on the first floor. The sharing space of the kitchen and the living room is in the center of the building, to save the floor area and the cost. Two bedrooms are on different sides of the kitchen, which make two independent personal spaces. An independent bedroom is set in each bedroom making them both master bedrooms.

This unit adopts separated air conditioning and heating system. The water heater is the most popular tankless type, hanging outside the wall to save the indoor space. The water meter and the electricity meter are also set independently.

Therefore, this plan fully takes cost-saving and space-saving into account. The ADU unit can be rented entirely or separately. It is independent physically and space-wise without affecting each other in use. Two master bedrooms also maximize the rental value.

adu fremont case study 5

Elevation plan

To ensure the adequate lighting of the ADU, build the ADU towards the backyard as much as possible and reserve a 15-feet transitioning space in between of two buildings. To take the cost into account, the roof is designed into sloped roof as the main house has. Choose consistent colors and materials with the main house to make two buildings look more coordinated.


(The project is unfinished)

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In interior design, the open kitchen connecting with the living is not the most spacious area, to make it look brighter and spacious, we choose white kitchen countertop and recessed ceiling light. As to the kitchen of a small ADU, finished cabinets are always the most affordable options for it. Installing finished cabinets can save time and cost for interior design.

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To save more space, the designer stack washing machine and dryer, and embed them in the kitchen. The compact design saves water and electricity, as well as the space.

In-Suite Bathroom and Closet
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The approval conditions of ADUs are becoming more and more relaxed due to encouraging city policies. Also, because of the increase in housing prices and low reserve of houses in the U.S., investing in ADU becomes an alternative great option in real estate. We hope a case study like this will help you with sorting out some ideas.


To see if your home is eligible for ADU in accordance with city code, please check out articles below:
Youtube Project Overview
$19,500 Fremont Project Video