The following research examines all new residential construction in the Boston metropolitan area between 1998 and 2002 and provides previously unavailable information on land consumption and housing density.
; The median lot size for new single-family houses was 0.91 acres, up from 0.76
between 1990 and 1998. The distribution of median lot sizes across towns was
quite varied, however.
; Multi-family land consumption, which includes both apartments and
condominiums, also varied across the region, but the median land per unit for the
region as a whole was 0.13 acres.
; Outside of Route 128, where the bulk of the region’s new construction is taking
place, the median single family house sat on 0.92 acres while the median multi-
family unit consumed 0.21 acres.
In addition, a town-by-town comparison of residential densities shows that only five places outside Route 128 are typically building on smaller lots than they have in the past.
Single Family Land Consumption
The median single family lot size for new construction in the Boston metropolitan area between 1998 and 2002 was 0.91 acres. The distribution across towns, however, is quite varied, with a marked difference between places inside Route 128 and places outside it. (See Map 1.) The vast majority of new construction took place beyond 128. New construction in the close-in 29 towns combined was equivalent to the amount of new construction in the top three towns—Plymouth, Taunton, and Haverhill—all of which lie
on the edge of the metropolitan area.
Just beyond Route 128, lot sizes for new homes jump significantly, with Lincoln, Weston, and Wayland each having medians above an acre. Along the Mass Pike, Natick and Framingham have medians between 0.25 and 0.5 acres, but almost all of the other communities between Route 128 and I-495 have much larger median lot sizes. Surprisingly, nearly all the towns bordering I-95 north of Danvers have median densities of more than an acre. Likewise, I-95 communities south of Weymouth have medians greater than 0.75 acres. Plymouth, which had the most new single family construction (1,390 new homes), has a median lot size of 0.71 acres. The more peripheral locations, even many along I-495, generally have very large median lots.
Multi-family Land Consumption
The difference between areas inside and outside Route 128 is even more distinct when examining multifamily construction. To calculate the amount of land associated with a given unit in a multifamily development, the total lot size for the development was divided by the total number of units in the development. Thus, each unit in a 20-unit development built on four acres would be allocated 0.2 acres. For the metropolitan area
as a whole, the median land per unit for new multifamily construction was 0.13 acres, about eight units per acre. (See Map 2.) About two-thirds of new multifamily construction occurred outside of Route 128. Multifamily units inside of Route 128 had a median land per unit of 0.05 acres, compared to a much larger 0.21 acres outside 128. (Note: City of Boston construction is not included here.) Quincy and Salem had the most new multifamily units, and they had median land per unit sizes of 0.05 and 0.06 acres, respectively. Weymouth, located just outside Route 128, had the most new units of all outer communities and had a median density similar to closer-in places. Other places with significant numbers of new multifamily construction include Marlborough, Lawrence, and Tewksbury, all of which lie on one, if not two, major highways. Not surprisingly, Lawrence, an old industrial city, has a median land per unit similar to places inside Route 128. The ―suburban‖ places with significant new multifamily construction have median land per unit values of just under 0.20 acres.
Multifamily units include rental apartments and condominiums, with a sharp difference in land per unit between the two. This difference holds true both inside and outside Route 128, with apartments built more densely than condominiums. Inside Route 128, apartments had a median of 0.03 acres per unit, compared to 0.06 acres for condominiums. Outside, the difference in land per unit between the two forms of tenure is even more pronounced, with the median apartment built on 0.11 acres and the median condominium on 0.29 acres.
Location Type Units Median Lot Size/
Land per Unit
Boston Metro Area Single Family 30,387 0.91 acres
Multi-family 14,362 0.13 acres
Apartments 5,047 0.06 acres
Condominiums 9,315 0.19 acres
Inside Route 128 Single Family 2,707 0.28 acres
Multi-family 5,157 0.05 acres
Apartments 2,323 0.03 acres
Condominiums 2,834 0.06 acres
Outside Route 128 Single Family 27,680 0.92 acres
Multi-family 9,205 0.21 acres
Apartments 2,724 0.11 acres
Condominiums 6,481 0.29 acres
Note to table: As described in Methodology below, the condominium numbers overstate the number of condominiums actually sold 1998-2002 because the calculations are done for ―full‖ buildings.
Comparison to Historic Densities
The region as a whole is using land less densely now than it has in the past. Single family lots built upon between 1998 and 2002 have a median of 0.91 acres. This is up from a median lot size of 0.76 acres during 1990–98, and double the new median lot for single-
family houses built during the 1970s and 1980s. Outside of Route 128, only five places (Chelmsford, Hull, Lawrence, Peabody, and Tewksbury) are building at lower density than previously. The towns in Plymouth and Bristol Counties that are inside the metro area are generally building at less than half their historic density. The phenomenon of new construction on lots considerably larger than those already built upon is not limited to the region’s periphery, however. Almost all of the towns along Route 128, I-95, and I-
495 are building on larger lots than they have historically done. Many of these towns have good access to suburban employment subcenters. (See Map 3 for average lot sizes for all new construction and Map 4 for a comparison to existing lot sizes.)
Data Sources and Methodology
The data for single family houses came exclusively from the Warren Group, which provided data on locations, lot sizes, and year built. For multifamily construction, the Warren Group data served as a starting point for identifying the presence of new multifamily construction. The Warren Group data is drawn, in part, from assessors’
records. In the case of condominiums, assessors allocate all the value in a development to the improvements, so they report neither value nor size for the underlying land. In order to find the size of the original parcel, we examined assessors’ maps and master deeds for the condominiums. Multifamily developments are often built in phases over a period of time. Because we were studying the density of newly built developments, we excluded units built as part of the final phases of earlier developments. We used 1995 as the earliest date for a master deed. For the purposes of allocating land per unit, we used the maximum number of units planned for each development, even if the later phases had not yet been built. We did this to more accurately reflect the ―true‖ density of the development. This methodology also ensured we were counting units built but not yet sold. Thus, the number of condominium units we have identified in the region is larger than those reported by the Warren Group. While we can identify specific years of construction for the single family houses, our methodology does not allow us to make similar comparisons across years for the multifamily developments. Nevertheless, the data allow us to accurately reflect and consider the residential land use decisions made just prior to and during the five-year study period.
Research Chief of Staff
Housing Affordability Initiative
MIT Center for Real Estate
andrewj [at] mit [dot] edu