A few observations on density
Feb 16, 2021 (w/Feb 17 addition of S. Normandy Ave.) – Several years ago I was thinking about the past, present, and future of Central Square and decided to simply take a walk through the Square with a camera with as objective an eye as I could manage. The result of that walk was something I called "Completing the Square" – a little math joke tied to the main observation that regardless of any opinions about how tall or dense Central Square may be or should be, there were lots of missing teeth and locations which could be improved by the presence of some new or enhanced buildings. That was before the new Mass & Main complex (now Market Central) was built.
In a similar vein, a couple of days ago I had the notion to do something of a virtual walk (in my head) along some streets with which I am quite familiar just to imagine how they might change under the proposed "Missing Middle Housing" zoning proposal. In my opinion, most of these streets function pretty well as they are and many of them (in particular those now zoned as Res C-1) would be considered pretty dense by any reasonable standard. I downloaded the City’s Assessors Database (thank you Open Data Portal!) and painstakingly reassembled all the living area information from the many condominiums in order to recreate the total living area to go with the total land area for each respective lot. (This was like reassembling puzzle pieces in some cases.) I then calculated the FAR (floor-area-ratio) for all lots on 28 representative streets (somewhat alphabetically biased as I went through them).
Prior to calculating some statistics on each of these streets I decided to exclude a few anomalies such as parks (no housing will be going there under any zoning revisions), municipal parking lots, City buildings (like City Hall, the Annex, DPW, etc.) as well as some lots that are in zoning districts unaffected by the proposed "Missing Middle Housing" zoning proposal, e.g. the Central Square BB district.
[You can view the data for each of these streets here.]
The summary sheet is below. Since there are already some nonconforming lots with FAR even greater than what is proposed in the petition, the increases noted below actually understate the increases under full build-out. On the other hand, it’s not likely that anything close to full build-out would happen any time soon (if the petition were to prevail), so this should be viewed more as a measure of what could eventually happen as opposed to what will happen in the near future.
Note that even a relatively dense C-1 street like Cherry Street in The Port could see a 66% increase in density. Chalk Street (Res C) could see a 72% increase. Cornelius Way could have a 175% increase (that’s 2.75 times the current density). Near me, Antrim Street could go up 47%, Maple Ave. could go up 84%, and Lee Street could go up 50%. In the leafy western "suburbs", a Res B street like Appleton St. could go up 137% (2.37 times the current density) and Lakeview Ave. (a mix of Res A-1 and Res B) would nearly triple in density. In contrast, Berkshire St. in Wellington-Harrington might only rise 2%, so I suppose this is the ideal street by the "Missing Middle" standard.
It’s also worth noting that there’s really nothing in the petition that would in any way ensure that the chief beneficiaries would be middle class residents. The petition is primarily a vehicle for increasing densities and this could just as easily translate into larger homes for those who can afford them or the freedom to add on significant additions to existing homes. In other words, the "middle" part of the "missing middle" petition is missing.- RW
| Street | zoning on street | total land area |
total living area |
gross FAR |
median FAR |
max FAR |
min FAR |
MM factor |
MM increase |
| Amory St. | C-1 | 166187 | 146798 | 0.88 | 0.89 | 2.25 | 0.00 | 1.40 | 40% |
| Andrew St. | C-1 | 39671 | 36841 | 0.93 | 0.94 | 1.46 | 0.44 | 1.33 | 33% |
| Antrim St. | C-1 | 215140 | 182351 | 0.85 | 0.85 | 1.59 | 0.45 | 1.47 | 47% |
| Appleton St. | B | 362349 | 167623 | 0.46 | 0.53 | 1.11 | 0.00 | 2.37 | 137% |
| Arlington St. | A-2,B,C-2 | 162551 | 82694 | 0.51 | 0.51 | 0.94 | 0.31 | 2.45 | 145% |
| Avon Hill St. | A-2,B | 159726 | 86824 | 0.54 | 0.64 | 1.04 | 0.25 | 1.95 | 95% |
| Bellis Circle | B,C-1A | 134257 | 86705 | 0.65 | 0.69 | 1.24 | 0.36 | 1.80 | 80% |
| Berkeley St. & Pl. | A-2 | 335663 | 147702 | 0.44 | 0.44 | 1.08 | 0.18 | 2.87 | 187% |
| Berkshire St. & Pl. | C-1 | 142900 | 162073 | 1.13 | 1.22 | 2.42 | 0.00 | 1.02 | 2% |
| Bigelow St. | C-1 | 98544 | 99178 | 1.68 | 0.99 | 2.48 | 0.55 | 1.27 | 27% |
| Bristol St. | C-1 | 105743 | 98448 | 0.93 | 0.89 | 2.09 | 0.34 | 1.40 | 40% |
| Brookline St. | B,C,BA-1,C-1,BB,SD9 | 462788 | 420848 | 0.91 | 0.88 | 2.59 | 0.00 | 1.41 | 41% |
| Buena Vista Pk. | C-1 | 58147 | 42787 | 0.74 | 0.75 | 1.05 | 0.46 | 1.67 | 67% |
| Centre St. | C-1 | 112030 | 118881 | 1.06 | 0.86 | 1.81 | 0.58 | 1.46 | 46% |
| Chalk St. | C-1 | 59707 | 40178 | 0.67 | 0.73 | 1.35 | 0.30 | 1.72 | 72% |
| Chatham St. | C-1 | 45415 | 43055 | 0.95 | 0.87 | 1.73 | 0.61 | 1.44 | 44% |
| Cherry St. | C-1 | 140624 | 83033 | 0.59 | 0.75 | 1.26 | 0.00 | 1.66 | 66% |
| Columbia St. | C1,BA,BB-CSQ | 419529 | 435148 | 1.04 | 1.01 | 3.33 | 0.00 | 1.24 | 24% |
| Coolidge Hill Rd. | A-2,A-1 | 155629 | 65633 | 0.42 | 0.55 | 1.85 | 0.00 | 2.26 | 126% |
| Cornelius Way | C-1 | 67640 | 31196 | 0.46 | 0.45 | 0.83 | 0.30 | 2.75 | 175% |
| Dudley St. | B | 162444 | 135259 | 0.83 | 0.83 | 1.48 | 0.24 | 1.51 | 51% |
| Hurley St. | C-1 | 185549 | 196004 | 1.06 | 1.09 | 2.45 | 0.42 | 1.15 | 15% |
| Inman St. | C-1 | 386571 | 347610 | 0.90 | 0.88 | 2.36 | 0.34 | 1.41 | 41% |
| Lakeview Ave. | A-1,B | 717287 | 299854 | 0.42 | 0.42 | 1.07 | 0.15 | 2.99 | 199% |
| Lee St. | C-1 | 184726 | 167663 | 0.91 | 0.83 | 2.17 | 0.48 | 1.50 | 50% |
| Maple Ave. | B,C-1 | 198500 | 132455 | 0.67 | 0.68 | 1.57 | 0.36 | 1.84 | 84% |
| Norfolk St. | C-1,B,BA | 445240 | 445634 | 1.00 | 0.88 | 3.31 | 0.00 | 1.41 | 41% |
| Pleasant St. | C,C-1,BA-3 | 387351 | 425992 | 1.10 | 0.93 | 2.27 | 0.36 | 1.34 | 34% |
| S. Normandy Ave. | B | 69538 | 24909 | 0.36 | 0.38 | 0.51 | 0.19 | 3.26 | 226% |
| all sample streets | 6181446 | 4753376 | 0.77 |
gross FAR = total living area divided by total land area
median FAR = median FAR of all lots on the street
max FAR = largest FAR for all lots on the street
min FAR = smallest FAR for all lots on the street (note that there may be vacant lots with FAR of 0)
MM factor = ratio of proposed "Missing Middle" FAR of 1.25 to current median FAR for street
MM increase = percent increase in FAR from current median FAR under full build-out
Well said, Robert. The only way that the MMH petition results in more mid-sized, middle-income housing is if it sets limits on maximum GFA per unit, while simultaneously allowing more GFA per lot. It does the latter but not the former, with the result being that it is more likely to generate larger existing homes than an increasing number of new homes. In the end, this will further escalate land values per unit, the lowering of which was one of the stated goals of the petition. In the end, the MMH will make it more expensive both to rent and also to own. At least in that sense it is a fairer petition than the AHO, which attempted to lower rental costs but also made home ownership even more challenging.
Comment by Doug Brown — February 16, 2021 @ 6:57 pm
In a market like Cambridge, if you want affordable housing, you have to build affordable housing.
Thanks for including my street, Hurley Street, in your calculations. I did a little calculation for my lot, which is dragging down your overall existing FAR, by the way. I live on an original East Cambridge lot of 5000 square feet. Under current zoning, I could have three dwelling units (only have one) and 3750 s.f. GFA, which would give average unit sizes of 1250 s.f. minus necessary common areas, like hallways and stairways. My current GFA is somewhere around 2100 s.f., which leaves enough open space to host the Hurley Street Neighborhood Farm, which grows an amazing amount of food, much of which is donated to food pantries (we are the hosts, not the people who do the work; those are fabulous Green Cambridge volunteers).
Under this proposal, we could have ten dwelling units and a total of 6250 s.f., which would give average unit sizes of 625 s.f., minus necessary common areas, like hallways and stairways. Those ten units would trigger the inclusionary zoning provisions, which would mean they could add three more dwelling units and 1875 s.f. GFA, for a total of 13 dwelling units and 8125 s.f. GFA, which would give, again, average unit sizes of 625 s.f., minus necessary common areas. Goodbye, farm. We would get inclusionary units totaling 1625 s.f. GFA, however they want to parcel that out. Does anyone think the ten other units would be cheap?
Comment by Heather Hoffman — February 16, 2021 @ 8:57 pm
Thanks for the very helpful analysis. Sadly, I’m even more pessimistic than Doug. The market price for new construction in a large amount of the city is flirting with $1,000 per square foot. This puts even moderately sized units well beyond the reach of middle income residents. This may create a powerful incentive for the replacement of modest multifamily buildings with larger more luxurious structures, thus fueling the replacement of those buildings’ current residents.
Comment by Peter Glick — February 16, 2021 @ 9:13 pm
Thanks Robert & others, this does seem like an important change to visualize in advance. Another symptom of density is how hard it is to find a parking space on the street, though at that point it’s usually too late. That symptom has become more noticeable in North Cambridge over the last few years as more backyard houses are built and a majority of small developments all across the city include garage removal with residential unit replacement. Where the symptom is noticeably absent is on streets like Lexington and Lakeview south of Huron, which are dominated by large singles on large lots with large garages in back. In a certain sense, the entire community benefits from these ‘luxurious’ properties. Please keep me in mind if you want some simple maps as worksheets or graphic displays.
Comment by george stylianopoulos — February 17, 2021 @ 10:48 am
I added South Normandy Street just to have a sample point in Cambridge Highlands.
(I also know several people who live on that street.)
Comment by Robert Winters — February 17, 2021 @ 11:25 am
These numbers are interesting, thanks. Three comments:
(1) Would it be easy for you to add a comparison of what “full buildout” would mean under current zoning? Likely for some streets (especially in Res B) that would be less than what currently exists, but for others it might be more than what currently exists.
(2) Since your FAR numbers are based on living area, rather than gross floor area, does that mean you are underestimating what is currently built / overestimating how much of an increase would be allowed?
(3) There’s a lot of examples of recent developments maximizing unit count wherever possible, which means I think we can forecast that these developments would likely produce more units rather than large new units. I haven’t personally checked this list that Chris gave me, but I’m posting for consideration:
“””
– 196 Pearl St
– 238 Pearl St
– 19 Florence St
– 24 Kelly Rd (slightly older)
– 300 Putnam Ave (built 16 out of 16 units allowed under base zoning)
– 226 River St redevelopment (which I believe still intends to be 3 units after redevelopment, though I could be misunderstanding the planning document); this was almost a complete interior rebuild, and could have gone for a single family interior, but elected not to.
On the other hand, existing zoning leaves the “creating a bigger house on the current lot” on the table on a regular basis: 384 Broadway (converted from 2 units to 1), 15 Gurney St. (which is going for a complete demo, having bought a $6M lot as a teardown, apparently).
“””
Comment by Allan Sadun — February 17, 2021 @ 12:27 pm
As unfinished areas are converted to actual living space, e.g. finished basements, those numbers are included.
As for multi-family homes becoming single-family homes, that’s the discretion of the property owner and it’s not so common that it should be a great concern – unless, of course, this is really all about control of property. It’s worth noting that many people who lived through the City’s rent control era understood that our laws were always more about controlling property than about controlling rents.
Specifically in the case of 384 Broadway up the street from me, that was a single-family home that became a school which then became multi-family and has now come full circle back to a single-family home. I don’t see this as a problem. It may have had other incarnations along the way. I hope nobody is suggesting that number of units should be ruled like entropy which can only increase.
Comment by Robert Winters — February 17, 2021 @ 1:21 pm
Based on your analysis, it seems like this will lead to a significant increase in the number of people that Cambridge can house. Since existing supply is not even close to meeting demand, that seems like a really good thing, right?
Comment by Aram Harrow — May 7, 2021 @ 1:02 pm
I can’t buy into the concept that Cambridge should house as many people as humanly possible – especially when other cities and towns in the region have much lower densities. Right now, Cambridge has a population density in excess of 16,000 per square mile which puts us (among cities with a population over 10,000) at #2 in Massachusetts and #26 in the entire USA.
I suppose if you lined every street of Cambridge with as much housing as you could physically pack in you would obviously be able to house more people – if that was your sole goal in urban planning. Many people, including me, feel that the prevailing density in most of Cambridge (and I’m thinking primarily of the Res C-1 districts) works pretty well right now. I think you can make a good case to raise the allowable densities (FAR) a bit in other parts of the city and I’m definitely open to the ideas of easing parking requirements and allowing multi-family buildings in all zones, but I am definitely not sold on the idea of jacking the allowable FAR to 1.25 in one shot all across the city.
Comment by Robert Winters — May 7, 2021 @ 9:53 pm