Creating a Home Building Machine
Zoning reforms, building code changes, and other rules to create a finer mix of densities and uses in currently single-unit zoned neighborhoods
Background
There has been recent movement to reduce the most extreme forms of exclusionary zoning in costly rental markets. California, Oregon, and other states and municipalities have rolled back “single-family” zoning, or development rules that restrict parcels to only one unit. California, for example, passed a series of ADU (accessory dwelling unit) laws that, when put together, have created a massive surge in permits for new in-law apartments.
The surge in permitting and inflow of capital into the newly legal and easily built ADUs has created a veritable machine of new housing construction. California also passed Senate Bill 9, which legalizes duplexes and lot splits in all currently single-family residential areas. However, there are some issues with the bill as Max lays out in the Twitter thread below that will have to be remedied to turn duplex construction into a similar machine to accessory dwelling units.
This article will detail the next step, from ADUs and duplexes to apartment buildings, from large lots on busy streets to small residential parcels, and from “stay or sell” to “mutual exchange.”
Zoning Reforms
Right now, in much of the cities of California, even if you have a house that is on a large enough lot and close enough location to support an apartment building, the maximum you can build on that lot is maybe 3–4 dwelling units. Cities should aim to go bolder in this regard by allowing upwards of 12–15 units on all currently single-family lots (how to fit 12–15 unit lots in a traditional single-family lot will be covered in the next section).
This doesn’t mean that the entirety of the city will become Manhattan or whatnot overnight. One of the central insights from Alain Bertaud’s Order Without Design is that land prices shape the feasible building and unit density in an urban area, not what the zoning allows.
To put it another way, if we allowed 12–15 unit apartment buildings on every parcel in California, they would not be built in far-flung exurbs such as Corona or Perris where land is cheap, but would be in well-connected transport hubs such as Miracle Mile or Santa Monica in the Los Angeles region where high land prices would force residents to economize and live in apartments or condos instead of in low density single unit buildings.
Similarly, in order to make these buildings viable, we need to eliminate mandatory parking minimums that drive up the cost of housing and, in this case specifically, make small lot apartment buildings less feasible due to the required parking taking up the lot instead of allowing more floor space.
Of course, allowing denser residential development is great, but denser residential development should also welcome commercial opportunities such as a convenience store or small restaurant or bar. Accessory Commercial Units, or ACUs, allow for small scale commercial enterprises in residential areas.
Rather than mandating ground-floor retail in large apartment developments as planners have traditionally done, legalizing ACUs allows for markets to respond to demand for commercial space in a much more fine-grained fashion compared to the current system of large commercial spaces with long leasing times. These kinds of small-scale commercial developments allow for an emergent order similar to that in Tokyo, creating a flexible private realm that more quickly responds to people’s changing preferences than large-scale apartment development.
So far, most land use intensification efforts have focused on commercial corridors or transit-oriented development, but in order to bring greater density and affordability to our most housing distressed regions, we need to understand that “single-family neighborhoods” should never be off limits to new development and change. Allowing accessory commercial units, apartment buildings with more units, and so on allow these traditionally off-limits-from-development neighborhoods to absorb the demand for new housing and commercial space.
Building Code Changes
The International Building Code governs building safety in the United States, including materials, accessibility, and most importantly for this section, requirements for egress (or escape in case of a fire). Requirements for multiple points of egress in the International Building Code were derived from New York’s 1901 Tenement House Act; insurance companies originally lobbied for egress requirements during the development of model building codes after World War 2 with the mistaken belief that the requirements were responsible for low levels of conflagration in NYC as opposed to the building materials.
However, construction techniques and fire safety have greatly evolved since 1901, implying that the International Building Code’s egress requirements are likely out of date. Building code reforms to align the United States with global best practices are in order, with the most crucial of these reforms being to remove second egress requirements in small apartment buildings. In other words, allow apartments to be built with one staircase (or staircase and elevator combination).
To start, let us address fire safety worries under this reform. One might think that the lack of a second stair would make the building unsafe in the case of a fire, but fire safety techniques have evolved past designing for tenants to escape in case of a fire. Architect Michael Eliason lays out some of these techniques and mitigations in a TreeHugger article:
Compartmentalization techniques in buildings attempt to keep fires from spreading past the room source.
Buildings can come with sprinklers that are highly effective at stopping fires.
Stairwells are pressurized to prevent fire and smoke from entering the egress route.
Apartment building materials are generally fire rated for 2–4 hours.
There are fewer units per floor (2–4) in a single stair apartment than in a typical apartment with so-called “double loaded corridors” (with units on both sides of a corridor and upwards of 15 units per floor).
Since these apartment buildings are smaller, the distance to the stairs and exit is lower than in a typical large-scale apartment building. German building code regulations specify a maximum distance from an apartment’s door to the stairwell.
These buildings can come with balconies that modern fire trucks can reach up to help people escape.
On the flip side, mandating multiple staircases in apartment buildings comes with many costs. These apartment buildings must have large floor plates, making smaller lot development less feasible — as the most exclusionary neighborhoods in large cities such as Los Angeles are those with lots between 5–6K square feet in a central location, lot assembly is hard if not impossible even in the absence of zoning barriers. By contrast, single stair apartment buildings can easily fit on a lot designated for single family houses, as seen by the picture below.
Not only are the floor plates large in these double loaded apartments, they are also inefficient. According to a report by Larch Lab, double loaded corridors require about 13% of their floor plate dedicated to “circulation” (or moving people around in hallways or stairwells), compared to a single stair “point access block” apartment with only 6.5% of the floor plate dedicated to circulation.
Point access apartments are not only cheaper per square foot of apartment than double loaded corridor buildings, but they can support floor plans with larger units such as 3 or 4 bedroom family-size apartments.
With all of these advantages in mind, it’s about time we legalized single stair apartments in the building code. With safety contingencies such as compartmentalization, fire sprinklers, and pressurized stairwells, it’s assurable that single stair apartments will keep their inhabitants safe.
Fees and Funding
Of course, simply legalizing single stair apartment construction through zoning reforms and building code changes will not be enough. To maximize the benefit of the single stair apartment reform in high demand urban areas and obtain buy-in from incumbent landowners, the government should encourage and facilitate land-for-condo swaps.
In Greece, after the adoption of the horizontal ownership law in 1929, a system known as antiparochi (approximately translated to “mutual exchange,” henceforth “land-for-condos”) developed where a landowner would to turn over their plot to a contractor in exchange for receiving an agreed-upon number of condos in the finished product; the apartment complexes became known as polykatoikia (“condominiums”) and form a central part of the urban landscape in Athens.
According to Cohabit Athens, one of the main advantages of the land-for-condos system was that it was very heavily tax-incentivized relative to other forms of development; the government charged a high tax on real estate transfers (reducing the return to purchasing a building without the intent to develop) while simultaneously allowing these redevelopments to commence nearly tax-free aside from a small payment.
Paired with liberal land use and building regulations, polykatoikia bloomed throughout the city, allowing the Athens metro area to absorb a doubling of population between 1951 and 1981. These apartments weren’t shoddily-built either, they were often respectable buildings with at-the-time modern amenities such as central heating and a diverse mix of incomes among apartment block residents.
In order to see success from an American land-for-condo system, we can learn these two major lessons:
Assessing high fees on new apartment construction while letting existing owner-occupied stock be nearly tax free will handicap such a system. In Greece, after the government started assessing an 18% tax on the received apartments, the number of apartment constructions fell sharply.
Facilitating this type of construction requires liberal, transparent rules from the municipal government rather than the current discretionary processes for apartments; this can be solved by taking inspiration from California’s ADU laws.
Additionally, the state government of California must reform construction defect law, which as written creates an excess of litigation (as California laws often do), increases construction insurance rates, and reduces the rate of new entrants into condo construction (keeping prices high). A public developer similar to one proposed in Alex Lee’s AB 2053 could not only further facilitate land-for-condos construction, but also take over projects from contractors or developers who may have gone out of business while in the process of construction.
In order to dig our country out of the staggering housing shortage, protect against pullbacks in case of increased interest rates, and reduce the dizzyingly high rents that are commonplace in high productivity cities, we need to go above and beyond the current strategy of duplexes and fourplexes and embrace single-stair apartment building in suburbs and underdeveloped urban residential areas.
While your other ideas (antiparochi/"Seattle Swap" and straight-up zoning reform) are good and necessary, there are some issues with the idea that single stair apartment buildings are a required or even important ingredient in densifying our cities, at least here in the USA. (Canada is in a subtly different position, as their building codes are even more restrictive than the US IBC is on this front.)
First and foremost, we have the issue that single stair buildings of 5+ stories require aerial fire apparatus as an integral part of their egress operations concept. This is something that's handled through per-building site plan analysis in Europe (Germany in particular), but with the less maneuverable stock of aerial apparatus we have right now in the US (adopting European bucket-style aerial units would indeed help somewhat, but that's a whole another kettle of fish), this requirement imposes rather undesirable spatial constraints on the site planning of neighborhoods. It also requires undergrounding of power lines, which while desirable, is a cost adder to infill construction, and interacts badly with overhead-powered transit lines. (I wonder if the Europeans use insulated booms/buckets on their aerial fire apparatus to work around this, similar to how power company bucket trucks are built?) Aerial apparatus may also not be widely available enough to be part of a "first due" rescue company response in suburban jurisdictions that only have a limited number of extant buildings that require its use.
With that piece of site planning out of the way, we get to the issues with the building itself. First off, while the Seattle single-stair amendment to the IBC in particular represents a strong effort to provide compensating controls for the lack of a second stair, it is unclear how they'd perform in a fire situation since I know of neither tests nor detailed modeling that substantiate them, just the relatively "back of the napkin" justifications provided so far.
This is something a local permitting authority (AHJ) could resolve fairly simply, though, as NFPA 101 (the Life Safety Code) provides a *performance-based option* the AHJ can use as a basis for plan review, where the architects are required to submit a set of fire scenarios and corresponding model results to the AHJ along with the building plans. In particular, NFPA 101 5.5.3.2 requires an analysis to be performed for a scenario that involves an extremely fast-growing fire that by its nature, blocks an egress means from the building (such as a car crashing into the main entrance to the building at a high rate of speed then immediately erupting into a fireball, or a bucket of solvent getting accidentally kicked off the roof and down the stairs, then igniting) while assuming that all interior doors are open at the start of the scenario. If a maximum-permitted-height single-stair building built to (say) the Seattle amendment package was able to provide a "no casualties from smoke or flames not intimate to ignition" performance in a well-validated whole-building smoke/fire model exposed to this scenario, that would be a major step forward in establishing that pushing this needle is indeed reasonable to do, at least in places where the problem I'm about to mention doesn't rear its head. This methodology also provides an evaluation path for the legacy NYC single stair amendments (which, while requiring the building structure to not be combustible, don't provide any compensating life safety controls for the occupants).
That other issue is the problem of safeguarding that single stair from smoke, which is a key compensating control in the Seattle single stair concept. To that end, the amendments provide two options: either an outdoor stair, or pressurization of the stair similar to how it's done in high-rises. However, neither of these options are all that practical outside of climates that are mild to warm year-round (namely the Southern US, the West Coast, and our various tropical islands). Outdoor stairs represent a significant snow and ice clearance difficulty in cold, snowy climates atop the hazard of abruptly having to egress into subfreezing weather (ask anyone who's lived in a Montreal plex or maintained a building with exterior corridors in a cold place before), while pressurization's devil is in the (mechanical) details.
In particular, to avoid building damage (frozen sprinkler lines and risers or even frozen plumbing pipes) or stairwell pressurization system malfunction (due to unwanted air flows) in cold climates, you need to *temper* the incoming pressurization air, something that imposes an exorbitant heat load on the building HVAC system. Even reaching a 50F air temperature in 0F outdoor conditions (roughly 99% winter design conditions where I live) requires massive BTU capacity, to the point where the heater for stairwell pressurization tempering is over twice as large as the heating plant for *all common areas of the building* under normal circumstances, based on my own "back of napkin" work. A heat exchanger could be employed to reduce this load, but could also pose controllability issues in situations where the system is actively exhausting elevated temperature air from the stairwell, and I haven't been able to find any use of such in my admittedly limited research.
This massive HVAC load translates directly into a massive *standby power* load on the building, which since we want to avoid a fossil fuel generator set (what good is it to build a Passivhaus and then stick a diesel engine on it?), means we need massive batteries. Massive enough, even, to trigger the IFC requirements for energy storage system fire control and suppression, which include sensitive (hinged panel -- rupture panels aren't sensitive enough to prevent building damage here) deflagration venting for the battery room, as well as a sprinkler system built to the equivalent of NFPA 13 Extra Hazard water delivery requirements (or in other words, six times the GPM per square foot that residential fire sprinkler systems put out). And we have to have enough water supply (flow and pressure) coming from the utility to feed that sprinkler system, wherever it is in the building, _without_ recourse to a fire pump, as that fire pump would mandate we need a generator _anyway_, defeating the point of the exercise.
Of course, all of this presumes that the stair pressurization system is correctly designed and the building as a whole is correctly maintained so that the stair pressurization system performs precisely as designed. Stair pressurization systems in their natural habitat (the high-rise building) are notoriously sensitive to building and environmental conditions, as well as to alterations to the building that increase air leakage rates into the stairwell or change the functionality of other air handling components.
However, even though single stair reform isn't a panacea, there are ways to arrange our buildings to provide many of its benefits while still meeting North American egress requirements. In particular, Brynn Davidson @Lanefab has done good work in this space, designing apartment buildings that fit on to 50' wide lots (or even narrower) while providing two egress paths from and two visible aspects to all units, using an approach that has units opening to two stairwells: one centered at the front, the other in the middle of the building's rear. It's also possible to build the equivalent of single-loaded buildings using a multi-stair strategy that feeds adjacent stairs directly from the units instead of relying on corridors to connect many units to a small number of stairs.
P.S. I'm posting this here since I haven't been able to find a way to reach folks involved in the single stair discourse without tangling with Twitter, which I have no desire to do.
The NIMBY problem is inevitable when a freehold of a title id made available for a parcel of land. This negates the idea that the land, as a resource, like the minerals beneath it, are a 'common', that should be enjoyed by the current generation. Inheritance laws allow the inequity to be carried forward from one generation to the next. Secondly, it arises as soon as planners insist on consulting neighbours before planning approval is provided, institutionalizing dog in the manger privilege. Thirdly, once one has this sort of segmentation it extremely difficult to change it. Your draw the map, you are stuck with it. Given this structure, there is always going to be an underclass, no matter how hard they work or how meritorious they might be. They can aspire to enjoy what they see others have, but they will never get it. All of the reforms recommended here need to be vigorously implemented plus some. Sad to say though, it amounts to tinkering at the edges. Its like pushing the brown stuff up the hill with a pointy stick.
Fortunately, those who are powerless and often victimized, both intentionally and unintentionally, by members of dominant groups have ‘‘adopted the dominant] group’s ideology and accept their subordinate status as deserved, natural, and inevitable, at least on the surface and until they decide to riot.
Its interesting to reflect on the fact that 90% of urban Chinese own their residence and that subsidizing rent for those occupying smaller residences is seen as a viable way of moving the economy towards a situation where local consumption drives production.
Its going to take a lot of Yimbyism to turn this around.