[logfromblammo]

Or the experience of row houses with basements. Natural lighting can be provided via light pipes and modernized deck prisms. If you want outdoor views, just go upstairs to street/garden level.

The whole idea is to remove the "dead" area that is currently solely occupied by residential feeder streets and suburban setbacks.

A 1/8 acre lot (0.05 ha) is 5445 sq.ft. (506 m^2). The average total square footage of new homes in the US is now over 2500 sq. ft., usually divided over at least two levels, making the lawn and garden for many lots at least 3 times the surface area of the house itself. You only need to reinforce the parts that people will actually drive over, and that space will likely be used for laundry, storage rooms, and utility closets. The utility corridors will likely be under the roads, so that's where your power, water, network, and sewer connections will come in to the house. People are a lot more accepting of windowless reinforced concrete bearing walls in their laundry room than in their bedrooms.

If the average lot size is 1/15 acre (0.027 ha), that's 2904 sq.ft. per lot, which is a lot depth of 88' (1/60 mi) with street frontage of 33' (1/160 mi). Give the public way an easement of 66', half out of the lots on either side, with 15.5' sidewalk and greenspace on either side, and 35' street. So on the ground level, you have 33'x35' of clear space, with 33'x20' of topsoil fill for the back garden, plus 33'x33' of space that may be obstructed by soil-filled tree pits, structural support for the street, and utility pipes and conduits. On the first floor, you have 2.5' setbacks between "houses", and 20' for the back garden, giving you 28'x35' of clear building area. Then you stack a third level atop that for another 28'x35'. That's about 3000 sq.ft. of interior space, with a 660 sq.ft. private garden, plus whatever is usable under the street and sidewalk. If basements are economical for that region, that's another 1155 sq.ft., minus the area for supports and bearing walls.

In one square mile, you can then have 30 parallel 2-lane streets with on-street parking, with 8 perpendicular 4-lane streets, for 8640 total buildable lots, each having more living area than the average McMansion. Assuming that you build 40% as parks, government services, and retail rather than residences, and an average occupancy of about 4 people per home, that's 20736 people per sq.mi., which could make your square mile the 14th most densely populated muni-corp in the US, without even having any multilevel apartment buildings.

[dpark]

I don't understand what issue you think this solves. You're describing houses that abut each other and are 3 stories tall. This would be a multi level apartment building if you didn't insist on making everyone stretch their living space across three floors and you didn't assume people want most of their housing to be in a basement. I don't think neighbors "driving across your roof" is a selling feature for most people, so I don't know who you think would prefer this over multi level apartments. Or perhaps more comparable, row homes.

From what I understand here, your proposal boils down to "make the lots half as big, build the houses directly adjacent to the street, and dig a basement that extends under the street to get some interior square footage". Yes, you could do this, or you could lift the whole thing up one level so the basement isn't really a basement (though I doubt it saves you anything since it's got to be a beefy structure to hold up to road traffic, and it's still going to feel like a basement). I just don't understand why you would do this and who would want to live in this Morlock ghetto. This sounds ugly and expensive and pointless when you could build dense housing without doing any of this.

[logfromblammo]

If you don't understand the problem, I have to assume you have never lived in a multistory walk-up apartment building with breezeway stairwells.

When I did, my wish-list was as follows.

  I wish I had...
  - a window that faced a different direction.
  - more storage space.
  - a parking space closer to my pantry, and at the same level.
  - better sound insulation between neighbors.
  - an unobstructed view of the southern sky.
  - more than one possible cable provider.
  - the option for DSL.
  - a uniquely numbered address.
  - a private outdoor space, suitable for gardening.
  - another way to get in and out of the complex.

When I moved to a freestanding house in a cookie-cutter suburban subdivision, all of those wishes were fulfilled, but I had new problems.

  I wish I had...
  - no accessible/visible lawn for the homeowners association to hassle me about.
  - a shorter/easier commute.
  - locks on my outdoor faucets, because of *that neighbor*.
  - any business at all within walking distance.
  - some sort of park within walking distance.
  - no visible ugly utility boxes.
  - lower total housing and utility costs.
  - a room that I could use as a home office.

Those are all the problems I think will be solved or reduced by my simplistic solution. Plus, there's the overall problem of cheap, dense housing that might still be accepted by Americans accustomed to typical suburban/periurban freestanding houses.