Getting the Height Right: the Importance of Context

This article was published in the CHALT newsletter, November 2014

Urban designers emphasize the importance of creating the right proportion between building height and street width. If the height of buildings along a street is too low relative to the street width, the space will evoke only a weak sense of spatial enclosure and will not feel particularly inviting; it may not feel like a distinct “place” at all. On the other hand, if the buildings are too high relative to the street width, they may evoke a canyon-like, claustrophobic feeling and deprive the street of the sun’s light and warmth for much of the day.

So what are the ratios that avoid these two undesirable extremes? Height-to-width ratios (HWR) ranging from 1:2 (i.e., building height equal to half the street width) to 1:1 (i.e., building height equal to street width) seem to be most highly preferred; these ratios produce buildings high enough (relative to street width) to create a clear sense of spatial enclosure and a well-defined street wall without being so high as to create a claustrophobic canyon.

For example, in Washington, DC, a very dense urban environment, there has been a law on the books for over 100 years limiting the height of buildings to the width of the adjacent street plus 20 feet. In DC, therefore, the HWR rarely exceeds 1:1. Similarly, in Toronto, urban designers determined that a 1:1 HWR is a good rule of thumb to follow when rezoning to promote higher density redevelopment.

In Ephesus-Fordham, we have some very wide streets, such as Fordham Blvd, and some much narrower streets, such as Ephesus Church Rd. and Elliot Rd. To achieve good HWRs—and, therefore, appealing streetscapes—throughout the district, one would want to permit taller buildings along Fordham Blvd. and lower building heights along Elliot Rd. and other secondary thoroughfares. This, in fact, is what the Ephesus-Fordham Small Area Plan proposed to do.

Unfortunately, however, the Town staff recommended, and the Town Council approved, a code that permits the same 90-ft building heights on both Fordham and on Elliot. Because Fordham is so wide, 90-ft buildings along that corridor conceivably could yield a ratio that falls within the desirable range, and, thus, an appealing streetscape. But Elliot Rd is only ~40 feet wide, or 60 feet if one includes the entire right-of-way. That means the HWR of the proposed 90-ft Village Plaza Apartments will be at least 1.5:1, well outside the preferred range and likely to create a cold, claustrophobic, canyon-like streetscape. Neither Washington, DC nor Toronto would permit the proposed Village Plaza Apartments to be built on a street the size of Elliot Rd.

Metrics such as HWR are one way to try to get the height right in Ephesus-Fordham, but it’s not the only way or necessarily the best way. Another way is to ask the town residents what building height they consider most appropriate or desirable. They, after all, are the ones who know the area best. When the Town staff and consultants put this question to the residents in a community survey as part of the Ephesus-Fordham small area planning process, the residents said they considered 2-3 stories the most appropriate height and density for the district.

In addition to asking the residents what they want, one can hire urban design professionals to recommend building heights. In the fall of 2013, Chapel Hill hired the urban design firm Placemakers to produce a form-based code guide for the Ephesus-Fordham district. They recommended that the central, highest density part of the district have a 50-ft height limit and that the more peripheral areas, such as Elliot Rd., have a 35-ft height limit. These recommendations accord quite well with the building heights envisioned in the adopted Ephesus-Fordham Small Area Plan (i.e., “1-3 story buildings along the fringes and 3-5 story buildings in the center”).

Thus, by three different standards—HWR, community preference, and expert opinion—our elected officials and Town staff got the height wrong when they adopted a code that permits 90-ft buildings along Elliot Rd. It’s not too late for them to go back and get the height right, by amending the code, but will they?

Further reading:
Mid-rise: Density at a human scale
Urban Scale

Share Button

Leave a Reply

Your email address will not be published. Required fields are marked *