Great Squares

I will add the image of the 5 minute walk and the idealized square frequency from Belgravia plus an image of Newport's proposed plan for London in 1666 (rejected) as well as Pietro Giacomo Cataneo's ideal city from 1567. You will note the similarities. I am not sure how to add these images so they may show up in the original post.

Over the weekend, I tried to unravel something that had been worrying me about the valuation assumptions. There is a point (from a developer’s viewpoint) where you have included too much green and your overall economics begin to crumble. As I have been working along on my London Squares project, this question has been in the back of my mind. I reviewed Andrew Miller’s price curve graph again from his MIT thesis and find it very believable, and similar to my experience in the sense that Andrew illustrates that value increases for being on or near an amenity drop rather quickly as one moves away from the amenity. Further, his suggested increase of 22% for frontage on a Square or park seems within reason. As one goes up the economic scale in terms of the market you are trying to hit, the increase for being on an amenity can be significantly greater than the 22% number, but what I did yesterday is create a little diagram to check the loss of standard lots in a grid plan against the increase of value that accrues to the lots near the created amenity. To do this, I created a grid 260 feet by 260. The grid need not be a perfect dimension from a planning point of view, but I needed a module that would allow me to check the loss of small lots against the increase in value. There are multiple reasons focused on the issue of a relatively small green space in the form of a square, but the math should be reflected of this conceptual approach to urban squares. I will upload the base diagram on my original Great Squares post. It will be the one with a green square in the middle and lot designations from A to D.

Bottom line, if you assume the value averages outlined below, there is a 32% increase in net revenues as calculated against the loss of revenues for the loss of lots in this 25 block analysis. I asked myself several other questions, one of which is also dealt with below in Alternative Two. The actual projected market increase that one would accrue in a specific location can vary a lot. So what percentage increase in value for a lot sitting on the amenity is the LOWEST percentage increase to at least cover the loss of the lots removed from the grid. The answer I came up with is about 17%. In other words, if you expect only to get a 10% increase in value for having a lot sitting on the amenity, you will have lost money for including the amenity. You need to get at least a 17% increase to warrant the introduction of the square. At least in this simulation. The introduction of the green hurt your economics rather than helped you.

There are two other simulations that I ran, but we will need some additional graphics to explain them. Briefly, I looked at what happens when another Square is introduced into the grid system. If you look a bit at the diagram above, you will note that there are lots in the 25 block area that have no increase in value (these are the D lots). Bottom line, we can put other squares into the grid system to improve the numbers overall. But how close is optimum?
I think the answer (assuming the 22% increase for A lots Andrew came up with) is not much closer diagonally than 900 feet. I ran two scenarios. One Square was 500 feet away diagonally and one was 950 feet away. The 950 feet diagonal spacing eliminated all “D” lots. Though the 500 spacing eliminated all D lots and upgraded others, the overall effect caused a net loss in value. I will try to upload an additional diagram later.

I assumed a grid system centered around a square that is created out of a full block, eliminating 26 townhome lots that are 20 feet wide and 120 feet deep. The square is 260 ft by 260 feet. "A" lots front directly on the Square. "B" lots are within 300 feet and the increase is priced at half the percentage that the"A" lots increase. "C" lots are between 300 and 600 feet from the Square and are half the "B" lot increase. "D" Lots are at the base price, being more than 600 feet from the Square.

Input base lot value: $50,000

Alternative One: No other Squares near by.
Input per lot increase in value of facing directly on Square: 22.00%
Figure a zone of 25 blocks with 13 lots of 20 feet wide each block face in one direction

Lot Type Projected Increase Increase/lot End Lot value Number of lots Total increases

A 22.00% $11,000 $61,000 52 $572,000

B 11.00% $5,500 $55,500 64 $352,000

C 5.50% $2,750 $52,750 290 $797,500

D 0 $0 $50,000 not counted $0

Total Increase: $1,721,500

For having created the Square, assume
that the loss of lots is 26 lots times $50,000 per lot -$1,300,000

Differential $421,500

Differential compared to loss of lots 132.42%

Alternative Two: At what increase is overall net a break even?
Input per lot increase in value of facing directly on Square: 17.00%
Figure a zone of 25 blocks with 13 lots of 20 feet wide each block face in one direction
Increase

Lot Type Projected Increase Increase/lot End Lot value Number of lots Total increases

A 17.00% $8,500 $58,500 52 $442,000

B 8.50% $4,250 $54,250 64 $272,000

C 4.25% $2,125 $52,125 290 $616,250

D 0 $0 $50,000 not counted $0

Total Increase: $1,330,250

For having created the Square, assume
that the loss of lots is 26 lots times $50,000 per lot -$1,300,000

Differential $30,250

Differential compared to loss of lots 102.33%
(Basically about even)

I have added to the images on the original post an excel analysis of Alternative 3 and Alternative 4 where Alternative 3 shows that a spacing of squares approxiamtely 950 feet apart on the diagonal appears to yield the highest possible economics.

Alternative 4 is also analyzed where a continuous linear park is considered. Before I looked at the numbers, I would have assumed that this configuration (linear) would have yielded decent results, but as calculated the results are quite negative. Instead of picking up $388,000 in Alternative 3 (the 950 foot spacing), we lose $836,000). The reason is that such a layout eliminates many more lots than the introduction of a modest square on a 950 foot spacing. It might be possible to improve the outcome by a tweak to the configuration of lots by introducing an additional alley mid block behind the A lots that would only run 120 feet to the main alley (a T configuration). This would allow the lots behind to front the streets perpendicular to the linear park and increase the number of B and C lots on these streets. However, a quick calculation makes me think the overall numbers will not improve - perhaps be even worse. I will also include the linear layout I used to compare to Alternative 3. The strange area chosen to calculate was so in order to have approximately the same number of developable lots.

My favorite from the Belgravia area is Egerton Crescent (for plan see www.cnu.org/node/715). There are many reasons it is noteworthy. For one, it is extremely effiecient from the point of view of maximizing frontages on green while not only minimizing the area of green but also the loss of developable lots. What follows is some preliminary data on Egerton Crescent.

Long Closure Ratio (B): 9.7:1
Across Middle Closure Ratio (B): 4.5:1
Green 110 ft. by 375 ft. at apexes.
Face to Face: longitudinally 475 ft.
Face to Face : middle 220 ft.
Radius to Face: 160 ft
Height A: 44 ft.
Height B: 49 ft.
24 houses on crescent proper plus 5 to each side.

Egerton Crescent (for midblock photo see www.cnu.org/node/714) arose during the mid 1840’s under the hand of James Bonnin, Sr. who had begun the slightly larger Pelham Crescent a decade before. The original mansion was demolished by the trustees of the Smith Charity Estate, and Bonnin was granted an 85 year sublease on what was then known as Brompton Grange in 1843 from his financier and speculator Stephen Phillips who has also been involved in the Pelham Crescent development. It is almost certain that Basevi provided design direction as he had at Pelham. The development was renamed at the latter part of the 19th century for Francis Egerton, one of the Charity’s trustees. The development was rapidly occupied, owing both to the economy of the time and the excellence of conception and execution.

The stuccoed crescent here is continuous, unlike Pelham Crescent, and has no break at its midpoint. Fifteen percent smaller than Pelham, the overall assemblage is more sophisticated – one of my favorite compositions in the district. There are many details to admire.

The architect solution to provide both differentiation and slight variations in square footage and height creates an overall rhythm of DAAAABAAAABCCBAAAABAAAAD. Additionally, the balconies run continuously for two to four units and then break at the units of emphasis.

Story height also varies, from the two one story end masses to the four story primary points of emphasis at the center. Windows distinctly change from level to level vertically and from unit type horizontally. This is done with great skill. The most elaborate windows are reserved for the four story quoined townhomes (the B unit s in the rhythm series). Vertically, the fenestration decreases in scale and pane size at each progressively higher level. Surface differentiation occurs as well, with the entry level fully channeled, whereas the upper levels are smooth surfaced.

Unity and continuity are achieved by a simple white palette throughout, a continuous cornice at the third story, and the repetition of consistent townhome types. Additionally, all entries repeat delicately scaled Ionic capitals atop fully dimensioned square pilasters which flank each entryway. An elegant and discreet awning system has been added for additional doorway protection which add a pleasant randomness since some are extended and some not.

The entry level plan for each unit is similar to the rest, being approximately 750 sf in area and differentiated primarily by door placement and window type. Each unit is approximately 22 feet wide. Ceiling heights are greatest on the second floor, which partially accounts for the particularly fine proportion of each individual façade.