HAWTHORNE ADU TOUR
GARAGE CONVERSION | 2 ADUS | 1 BED, 1 BATH EACH
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Turns out 40 sq ft IS a big difference. Check out how a 400 sq ft ADU compares to a 440 sq ft ADU. Both are different, but equally functional, comfortable, and effective.
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Unit A - 440 Sq Ft 1 Bed, 1 Bath
Unit B - 400 Sq Ft 1 Bed, 1 Bath
400 sq ft vs 440 sq ft ADU: How 40 Square Feet Changes the Layout - Real World Example
1 BED | 1 BATH
If you’ve ever heard me talk about ADUs, you know I get fired up about smart design, especially when we’re working with tight square footage. In this project, I’m walking you through two near-identical ADUs on the same property, built side by side, with just a 40 square foot difference: one is 400 sq ft, the other 440 sq ft. Same lot, same conditions, same goals… but noticeably different layouts once you get inside.
These units came from the conversion of an existing 4-car garage on a property that already had a duplex. Thanks to the SB9 duplex provision, we were able to add these two ADUs, bringing the property to four total units.
In this walkthrough, I break down why certain design choices were made and how every single square foot had to earn its keep. These are the exact design tradeoffs we think about on every ADU we build, and I’m excited to show you how small changes in size can lead to very different (and very intentional) results.
Hawthorne ADU Project Overview
Before we get into the layout details, here’s a quick snapshot of the project so you can understand the full context, because this setup is a big part of what made these designs possible.
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Existing Property: Duplex (2 existing units)
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Original Structure: 4-car garage
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Project Type: Garage conversion into two separate ADUs
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Planning Path: SB1211 2 existing units + 2 ADUs
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Final Property Count: 4 total units
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Unit A: 400 sq ft, 1 bed / 1 bath
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Unit B: 440 sq ft, 1 bed / 1 bath
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Location: Same property, same footprint, same constraints
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Use Case: Long-term rental
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Designed and Built By: Joseph Peretz of NeoBuilders
What makes this project especially interesting is that both ADUs came from the same 4-car garage structure. No ground-up build, no extra square footage added, just smart planning, careful design, and a deep understanding of what SB9 allows. With only a 40 sq ft difference between the two units, this setup creates the perfect real-world comparison of how small shifts in square footage can dramatically impact layout, flow, and functionality.
Kitchen Layout: Single-Wall vs L-Shape
When I design a kitchen, especially in an ADU, there are three things I look at first, every single time:
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Overall kitchen layout
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Location of the sink
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Washer/dryer placement
Those three decisions drive everything else. Cabinets, appliances, cost, flow; it all starts there.
Kitchen A: 440 sq ft ADU – Linear Kitchen with Peninsula
In the 400 sq ft unit, we went with a linear (single-wall) kitchen, and that decision was very intentional.
All the plumbing is located on one wall, which immediately:
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Keeps construction costs down
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Makes the kitchen more efficient
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Simplifies future maintenance
Everything in this kitchen is easy to access, but because a straight-line kitchen can feel a little exposed, we added a peninsula. That peninsula does a lot of heavy lifting:
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It creates a clear separation from the living room
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Adds seating for two
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Provides extra storage without closing the space off
The sink is centered on the wall, directly under a slightly wider window, which brings in more light and makes the kitchen feel bigger than it actually is. We used an undermount sink to keep the look clean and seamless.
For washer/dryer placement, this is pretty typical in a linear kitchen: it sits next to the refrigerator, keeping all the larger appliances consolidated in one efficient run.
Kitchen B: 400 sq ft ADU – L-Shaped Kitchen
This is where things get interesting.
Even though Unit B is smaller at 400 sq ft, we opted for an L-shaped kitchen. Why? Because the layout allowed us to be more strategic with how the space was divided.
The L-shape:
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Feels more compact and intentional
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Provides more storage than a straight-line kitchen
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Makes better use of the corner
One of the biggest wins in this unit is the hidden washer/dryer. Instead of being out in the open, it’s tucked away between the bathroom and bedroom and enclosed on three sides, making it almost disappear. Something that’s harder to pull off in a linear layout.
Two different kitchen strategies, each designed to make the most of the space available.
Bathroom Design: Same Footprint, Very Different Experience
Bathrooms are another place where small dimensional changes make a big difference. When I’m designing a bathroom for an ADU, I always focus on three core factors:
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Bathroom layout
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Overall bathroom size
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Shower design
These decisions determine how open the bathroom feels, how much storage you get, and whether the space feels functional or tight, especially at this scale.
Bathroom A: 440 sq ft ADU – 5' x 8' Bathroom
Bathroom A measures 5 feet by 8 feet, making it half a foot smaller than the bathroom in Unit B. Because of that, everything here had to be extremely intentional.
When you enter, the door opens directly toward the vanity and toilet. That means slightly less privacy, but the tradeoff is that the room feels more open and usable overall.
Key design choices in Bathroom A:
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30-inch vanity, which directly correlates to the smaller bathroom size
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Shower and toilet sized at the minimum dimensions we’re comfortable with
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Built-in shower bench, which adds functionality but takes up visual space
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Chevron tile to add movement and visual interest
Even with the tighter dimensions, this bathroom doesn’t feel cheap or cramped. That’s where details matter.
Bathroom B: 400 sq ft ADU – 5' x 8.5' Bathroom
Bathroom B is just six inches larger, at 5 feet by 8.5 feet, but that extra half foot completely changes how the space works.
Here, the door opens directly in the direction of the shower, which immediately makes the shower the jewel of the room. The toilet is tucked off to the side, providing slightly more privacy than in Bathroom A.
Key design differences in Bathroom B:
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36-inch vanity, made possible by the additional depth
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Vertical subway-style design using the same tile as Bathroom A, just installed differently
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No shower bench, which makes the shower feel noticeably more open
Even though both showers are the exact same size, the shower in Bathroom B feels larger simply because there’s no bench breaking up the space.
Shared Features in Both Bathrooms
To keep quality consistent across both units, we used the same core upgrades in each bathroom:
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Mirror and medicine cabinet
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Linear shower drain
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⅝-inch custom shower glass
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Brush brass plumbing fixtures
These are two bathrooms that feel very different because of how the space was allocated and prioritized, but they still deliver efficient usability and a high-end feel.
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