Planning: Block Sizes for Medium Lots

NB: I believe this topic has been discussed much better many times elsewhere on the net and in print.  I am writing simply to clarify my own thoughts.  I apologize for the primitive graphics.

In a previous post I discussed the block size for a lot that is at the large end of the spectrum for American urban areas.  I concluded that the lot worked well within the block size I had selected.  But what about smaller lots, closer to what can be found in older sections of American cities?

This configuration, with lots 60' wide, is basically the same as with 80' lots.  The density increases by about 25%, but it is still car-oriented.  Each lot has an ample back yard, and plenty of room for off-street parking.  There is no obvious reason to increase or decrease the block depth, and block length should be at least 900' to keep taxability high.

The next step down in lot size is 40', increasing the density again, this time by 33%.  In this configuration, the appearance of the house from the street is dominated by the garages.  This form has been dubbed the "snout house."

Here I have depicted a 28' wide house with both single and double garages.  In the latter case, the house is barely wide enough to allow for a human-sized front door next to the garage.  And in both examples, the front yard is dominated by the hard surface of the driveway.  The back yard shrinks considerably on these lots as the footprint of the home is roughly the same size as on an 80' lot.  However, if the outdoor parking in front of the garage is discarded, it is possible to bring the home forward in order to expand the back yard.

But this adjustment just brings unfriendly garage doors closer to the street, giving the public space an appearance similar to that of an alley.  Another possibility is to move the garages out of the mass of the home and into the back yard.

This alteration would improve the appearance of the home and street, but the yard would have vastly more hard surface, increasing the problems of storm runoff and the urban heat island.  And it would change what activities that could be pursued in the back yard. 

	80' w/ long driveway	60' w/ long driveway	40' w/ long driveway	40' w/ short driveway	40' w/ rear garage
Gross length	900	900	900	900	900
Gross depth	300	300	300	300	300
ROW width	60	60	60	60	60
Net length	840	840	840	840	840
Net depth	240	240	240	240	240
Lot width	80	60	40	40	40
Lots per block	22	28	42	42	42
Parking – private	4	4	4	2	7
Parking – street	1.5	1	0.5	0.5	0.5
Driveway	610	610	549	297	1355
Pct. paved	6.35%	8.47%	11.44%	6.19%	28.23%
Back yard	5360	3360	1680	2320	1380
Pct. back yard	74.44%	46.67%	23.33%	32.22%	28.75%

More importantly, the number of driveways and curb cuts remains the same in all of the 40' lot configurations, each of which increase the chances of vehicle-pedestrian conflict, and reduces the amount of on-street parking.  40' wide seems to be the lower limit for front driveway lots.  The block length remains acceptable as the density is still below general walkability.  The lots would be larger if depth was increased, but there's no particular reason to think the lots are overly small, other than personal preference.  I will look at a different block layout in a future post.