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Alfred Twu @alfredtwu.com

#Berkeley Middle Housing upzoning takes effect on Nov. 1, 2025, allowing 8 homes on a typical lot in most of the previously low-density zones in the city, and more if state Accessory Dwelling Unit and Affordable Housing Density Bonus laws are used. Here's a look at some possibilities! 1/

Berkeley Middle Housing 柏克萊中型住宅 R-1, R-2, R-2A, MU-R Zones R-1, R-2, R-2A, MU-R 區 5,000 square foot lot 5,000 平方英尺地塊 3D drawing of a city block with various types of housing Picture: a 2-story house with a 3-story building in the backyard Backyard Apartment Existing House + 3-6 new apartments 後院公寓 現有房子 + 3 - 6 間公寓 Picture: Two 3-story buildings each with 2 doors Double Duplex 4 units, total of 20 bedroom suites 雙子雙拼住宅 4 間住房 一共 20 間套房 Picture: 5 three-story townhouses along a path perpendicular to the street Townhouses 4-6 townhouses 聯排屋 4-6 棟聯排屋 Picture: a 3-story apartment building with a 2-story building behind it. 8+8+2 8 apartments + 10 ADUs 八加八加二 8 間公寓 + 10 間附屬住宅 Picture: a skinny 6-story apartment building Density Bonus 16 apartments + 4 ADUs 密度獎勵 (兩塊地) 16 間公寓 + 4 間附屬住宅 Picture: a cube shaped a 6-story apartment building Density Bonus (2 lots) 32 apartments + 8 ADUs 密度獎勵 (兩塊地) 32 間公寓 + 8 間附屬住宅 Note: Restrictions apply to demolition of existing rental housing 註:法律有關於拆除現有租賃住宅的限制 CC-BY: Alfred Twu 姓名標示:涂顥曦 alfredtwu@gmail.com 2025.07.29
jul 30, 2025, 4:39 am • 168 28

Replies

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davidtaylor555.bsky.social @davidtaylor555.bsky.social

Can you show some construction cost and income pro formas for each type, including the land/teardown cost in lower and higher cost areas?

aug 1, 2025, 4:54 am • 1 0 • view
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Alfred Twu @alfredtwu.com

Good idea, will do!

aug 1, 2025, 6:12 am • 0 0 • view
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Spencer Heckwolf @spencerheckwolf.bsky.social

Are those townhomes subject to the same impact fees?

aug 1, 2025, 10:12 am • 0 0 • view
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Alfred Twu @alfredtwu.com

Yes, fees are same for all types of housing, however, the first 5,000 square feet is exempt from Berkeley's inclusionary housing fee. State law exempts ADUs under 750 sq ft each from all impact fees, and ADUs under 500 sq ft from school fees also - see page 22-23 of www.hcd.ca.gov/sites/defaul...

aug 1, 2025, 3:23 pm • 0 0 • view
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joshisposh.bsky.social @joshisposh.bsky.social

Alfred you are the absolute boss

aug 1, 2025, 4:02 pm • 1 0 • view
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Alfred Twu @alfredtwu.com

Thanks! 🏠

aug 1, 2025, 4:04 pm • 0 0 • view
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Coba Weel @weel.bsky.social

Does the single lot density bonus project have an elevator?

aug 1, 2025, 3:26 am • 1 0 • view
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Alfred Twu @alfredtwu.com

Yes

aug 1, 2025, 3:39 am • 2 0 • view
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Alfred Twu @alfredtwu.com

Here is a map of the parts of #Berkeley that the Middle Housing zoning change apply to - PDF is at berkeleyca.gov/sites/defaul... The full text of the Middle Housing ordinance is at berkeleyca.gov/sites/defaul... The new zoning allows 3 story buildings (this can be increased by Density Bonus). 2/

Berkeley Zoning Map, showing areas upzoned by Middle Housing highlighted. This includes most of the city west of Shattuck, as well as the area south of Dwight and west of Claremont. The zones are various shades of yellow and orange labeled R-1, R-1A, R-2, and R-2A, plus a thin strip of blue MUR at the west. The hills, commercial streets, downtown, and Southside, and industrial areas in west Berkeley are not shaded.
jul 30, 2025, 4:44 am • 18 0 • view
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Alfred Twu @alfredtwu.com

State laws that allow additional homes: Affordable Housing Density Bonus 🏠 Up to 100% more units if some are for low/middle income Accessory Dwelling Unit (ADU) law 🏠 Existing building can increase number of units by up to 25% by converting garages, storage, etc. 🏠 Can add up to 8 detached ADUs 3/

jul 30, 2025, 4:47 am • 11 0 • view
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Alfred Twu @alfredtwu.com

For details: California Density Bonus law leginfo.legislature.ca.gov/faces/codes_... California ADU handbook www.hcd.ca.gov/policy-and-r... 4/

jul 30, 2025, 4:49 am • 6 0 • view
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Alfred Twu @alfredtwu.com

Of course, not everyone will build to the maximum density. There's no requirement to do anything at all, people are free to keep their house as-is as a single family house. In other cases, a lower-density development may make more sense personally or financially. Let's look at some examples. 5/

jul 30, 2025, 4:51 am • 12 0 • view
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Alfred Twu @alfredtwu.com

Many Backyard Apartments already exist in Berkeley, built before the 1970s downzone. This design works well on deeper lots where the existing building already has someone living in it, whether it's a homeowner who wants to stay, or tenants, who have protections under Berkeley law. 6/

Berkeley Middle Housing 柏克萊中型住宅 Picture: a 2-story house with a 3-story building in the backyard Backyard Apartment 後院公寓 Line pointing to house in front: Existing House 現有房子 Line point to 3-story building in back 3-6 new apartments 3 - 6 間公寓 Note: Restrictions apply to demolition of existing rental housing 註:法律有關於拆除現有租賃住宅的限制 CC-BY: Alfred Twu 姓名標示:涂顥曦 alfredtwu@gmail.com 2025.07.29
jul 30, 2025, 5:04 am • 15 0 • view
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Alfred Twu @alfredtwu.com

With 3 stories allowed under the Middle Housing zoning (which is also the maximum height allowed before 2 stairs are required by the building code), a backyard apartment building easily fit 3 two-bedroom homes, or up to 6 studio apartments. 7/

jul 30, 2025, 5:06 am • 11 0 • view
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Alfred Twu @alfredtwu.com

The Double Duplex is a type of housing in Los Angeles that could become common in Berkeley also. Popular with students and other singles, each bedroom suite has its own bath and is rented separately. Since each building only has two kitchens, it can be built using the simpler Residential Code. 8/

雙子雙拼住宅 Double Duplex Picture: Two 3-story buildings each with 2 doors Each one is labeled as: Duplex Each half has 5 suites 雙拼住宅 每半有 5 間套房 4 Units, total of 20 bedroom suites 4 間住房, 一共 20 間套房
jul 30, 2025, 5:19 am • 12 3 • view
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Matt da Silva @mdasilva.bsky.social

Why this and not a single 6-8 unit apartment building?

jul 30, 2025, 1:05 pm • 1 0 • view
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Stephen Jacob Smith @stephenjacobsmith.com

IRC vs. IBC, and all of the related threshold regulatory issues that crop up when you move from the land of single-family-ish houses to apartment buildings

jul 30, 2025, 1:06 pm • 5 0 • view
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Coba Weel @weel.bsky.social

So the threshold is two units per building? And units of course are defined by kitchens and kitchens by stoves and stoves by gas hookups or stove outlets? Are we gonna be seeing a lot of “wet bars”?

aug 1, 2025, 12:58 am • 6 0 • view
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Alfred Twu @alfredtwu.com

Many single-house examples already exist in Berkeley. A type of group living, they're also known as Co-Living, Mini-Dorms, or simply living in a house with roommates. I've written more about Double Duplexes here, with some example floorplans ordinaryhomes.blogspot.com/2023/07/doub... 9/

jul 30, 2025, 5:23 am • 15 0 • view
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Alfred Twu @alfredtwu.com

The latest on Double Duplexes in this article by @henrygrabar.bsky.social. They're common in Los Angeles, especially near the University of $outhern California, where most students live off-campus. bsky.app/profile/henr...

aug 1, 2025, 6:26 am • 6 0 • view
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javi 🏳️‍⚧️ @javi.beesky.social

thank you for spelling the school's name correctly

aug 1, 2025, 6:50 am • 1 0 • view
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Alfred Twu @alfredtwu.com

Another Double Duplex article, this one from @futureis.la bsky.app/profile/futu...

aug 1, 2025, 6:42 am • 11 3 • view
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Alfred Twu @alfredtwu.com

Since most new homes built in Berkeley are rental apartments, there's a shortage of homes for sale. As a result, townhouses are likely to be popular under Middle Housing. Using state law SB684/SB1123, a lot can be subdivided so that each townhouse is on its own piece of land. 10/

Berkeley Middle Housing 柏克萊中型住宅 Picture: 5 three-story townhouses along a path perpendicular to the street Townhouses 聯排屋 Arrows label the houses 1 through 5 Note: Restrictions apply to demolition of existing rental housing 註:法律有關於拆除現有租賃住宅的限制 CC-BY: Alfred Twu 姓名標示:涂顥曦 alfredtwu@gmail.com 2025.07.29
jul 30, 2025, 5:33 am • 12 0 • view
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Alfred Twu @alfredtwu.com

Known as Small Lot Subdivisions in Los Angeles, this type of townhouse project is becoming popular in Silicon Valley as well. Parking is hard to fit on a 50-foot wide lot, however, if two lots are combined, it's easier to do a shared driveway. ordinaryhomes.blogspot.com/2023/11/slot... 11/

jul 30, 2025, 5:38 am • 12 0 • view
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Geo NV @geonv.bsky.social

Any adjustment to the maximum lot coverage rules?

aug 1, 2025, 2:04 am • 2 0 • view
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Alfred Twu @alfredtwu.com

Lot coverage is 60% max, which is close to what's physically possible after subtracting the required yards. Both the lot coverage and yard regulations can be waived if a project provides low or middle income housing for a density bonus.

aug 1, 2025, 3:39 am • 2 0 • view
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Geo NV @geonv.bsky.social

is hardscape still included in lot coverage, or exempted now?

aug 1, 2025, 2:27 pm • 1 0 • view
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Alfred Twu @alfredtwu.com

Lot coverage only includes buildings. Outdoor walkways, patios, etc are excluded.

aug 1, 2025, 3:08 pm • 1 0 • view
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Geo NV @geonv.bsky.social

That's good to hear. Was pretty sure hardscape was included last time I read the code, but that was years ago.

aug 1, 2025, 3:17 pm • 1 0 • view
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Nathan McDermott @nathanmcdermott.bsky.social

Love your artwork!

jul 30, 2025, 1:10 pm • 3 0 • view
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Alfred Twu @alfredtwu.com

Thanks!

jul 30, 2025, 2:26 pm • 2 0 • view