Building Height and the Overlay
Under Cambridge's proposed Affordable Housing Overlay, developments which are dedicated completely to units available only to households making below the area median income would be allowed to exceed the height allowed under current zoning in many districts. However, there's been a lot of misunderstanding of what this would look like in practice. To help give a sense of what these increase look like, here are some examples in context of their street to give a sense of what the allowed height increases could look like throughout Cambridge.
Residential Districts
In most of the city, this increase in allowed height is relatively small: 85% of the City is in districts that would be allowed only a slight height increase from the currently 35' to 45', or 50' with an active ground floor use like a restaurant or storefront. With or without an active ground floor use, these buildings would be limited to only 4 stories tall.
On the map to the right, you can see the areas of Cambridge that fall into this category. This includes the vast majority of the city's residential neighborhoods. This means that for almost the entire city, the overlay will create buildings that are similar in height to what already exists.
Residential Overlay Height Example
To give a sense of what the maximum height of buildings under the overlay would look like in a typical, residential context, we'll take a sample street. These images represent the northern side of Garfield Street. (You can explore this area on Google Maps to get a better feel for the scale here.) The four story brick apartment building pictured here is slightly more massive than would be allowed under the overlay -- because it was built before zoning was introduced in Cambridge, it has no side yard setbacks, and so would need to shrink on both sides to actually be allowed, but it gives a decent sense of scale. This particular example is in a district which is currently zoned "B": the two-family residence zone that is common in much of the city.
While opinions will always differ on how out of scale a building is, overall, the relative height increase of 45' tall, 4 story buildings is only moderate, even in residential zones like this one, relative to the surrounding buildings.
This street in the Agassiz neighborhood is a typical example of a Residence B neighborhood. Pictured here are three homes, with a slightly taller brick building at the far left side of the image -- slightly taller than what would be allowed under the overlay, at just over 45'. The homes pictured here are 42', 40', and 37' tall (from right to left).
The building pictured on the left here is a building that is the maximum the overlay allows. In this particular case, it would not be allowed to be built in this way -- the building has insufficient setbacks but it can give a sense of the maximum scale of these buildings in residential neighborhoods.
This illustration on the other side of the building gives a better sense of the setbacks required: while this setback crosses the property line, the gap between the buildings here would be close to the minimum side yard setback allowed under the affordable housing overlay.
Increased Height Along Corridors
In districts that already allow 45' tall buildings or higher, the proposal increases the allowed height as well. As of the most recent ordinance committee amendments, there are now two different categories of height allowance:
- In the "BA" and "BA-2" districts (marked in purple on the map), the allowed height is 6 stories, with a height of up to 65'. This is largely a set of properties along Cambridge Street (east of Inman Square) and Massachusetts Avenue (north of Harvard).
- In the remaining zones with allowed heights above 40' but up to 80', buildings are allowed to be built to 7 stories, with a height maximum of 80'. This applies mostly to the Alewife district; Massachusetts Avenue between Central Square and Harvard Square; and Porter Square. It also includes two industrial zones -- one between Cambridgeport and MIT, and one north of Kendall Square, in a district which is currently largely built up of lab space near Bent Street.
In each of these districts, areas which are within 35' of a lower height zone have a lower height allowance: they are allowed to only reach 4 stories and 47' for the lower zone, and 5 stories and 60' for the higher zone.
Map of areas where additional height is newly allowed over the 4 story limit for most of the city. (See the Building Height: Expanded Maps page for expanded maps that show each neighborhood more clearly.)
What does 6 stories look like? What does 7 stories look like?
In these districts, buildings close to this height are already in existence throughout Cambridge (often in districts where they wouldn't be allowed even under the overlay). To get a sense of this in the context of these areas, we can look at 6 or 7 story tall buildings in these areas today.
50 Follen St (6-story example)
50 Follen St is a 6 story condo building built originally in 1925. This building tops out at 65' tall -- the maximum allowed under the middle height zone in the overlay proposal as amended on 2019-08-08. This property abuts a lower district A-1 zone, next to a 38' tall single-family style building. Because of that, it would be limited to only 4 stories and 47' in height on the side which is closest to the single-family style building next to it. Similar to other cases, there are aspects of this building that would not be allowed in all districts -- for example, side yard setbacks would be required in this middle height zone -- but it provides a reasonable approximation of height relative to neighboring context.
While this building may look imposing in this context, it's worth noting that the streets this height would be available to build on is largely along Massachusetts Ave. or Cambridge Street, which are already populated with buildings taller than the typical single family home.
Along Waterford St., looking east towards 50 Follen St.
Along Waterford St., looking west past 50 Follen St.
881 Massachusetts Ave (7-story district)
This building was built in 1873, and contains 56 units. In a dense area of Massachusetts Ave, this 7 story tall, 72 foot tall building is only slightly under the maximum height allowed under the overlay. An overlay building built today would likely have a slightly taller first floor to meet modern building requirements, but otherwise would look similar in bulk and massing. This is an example of the 7 story, 80' cap allowed in some sections of Massachusetts Ave and Alewife.
Because this lot backs up to a residential building in a lower height district, it would be required to lower its height in the rear to a maximum of 5 stories and 60'.
Looking at 881 Massachusetts Ave from the east.
Looking at 881 Massachusetts Ave from the west.
Existing rules establish minimal setbacks along corridors, allowing for building of street walls.
Existing Taller Districts
Where districts allow taller buildings today, the overlay does not affect those heights: that is, for the few districts in Cambridge which already allow buildings to be 120' tall, the overlay does not prevent affordable housing built under the overlay from reaching those same heights. This applies to a very small portion of Cambridge -- about 2% of Cambridge properties above allowed heights above 80' today, largely in large, institutionally owned parcels or in Planned Unit Developments (PUDs) which would not be redeveloped with affordable housing. While these areas make up a lot of the land of Cambridge, they are largely not areas that are available for redevelopment for housing.
The map to the right highlights these parcels in Cambridge today, which are largely made up of large areas of MIT and Harvard-owned property, or the areas directly in Harvard Square and Central Square, which have a maximum height at 80' and would not gain any new height under this proposal.
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