What Makes Sites Inefficient?
In a previous post, we talked about rules of thumb for density based on lot sizes and product types. As those are essentially just rough estimates, the actual density achieved on a site can vary based on a variety of factors.
One key factor is the amount of slope on a site. This slope needs to go somewhere and can typically be 2-to-1 (horizontal to vertical) grades between lots or buildings. The use of retaining walls can help with reducing slope and increasing flat pad area, but these retaining walls can be costly – particularly the taller the walls. Keep in mind, though, that this slope can have some benefit by creating space and privacy between homes.
Another key factor is the ability to have double-loaded streets, which means you have homes on each side of the street. If the site plan design cannot avoid single-loaded or even non-loaded streets, the efficiency and density can suffer. I have seen flat, square sites that do not maximize density because the parcel dimensions cannot accommodate street circulation with all double-loaded streets. Conversely, a narrow and rectangular site might be ideal for one double-loaded street that does maximize the site.
Another element that can impact density is the number of access points for a site. Without two points of access, cul-de-sacs are often necessary – largely to provide a turning area for fire trucks. These culs add to your street area and take away from lots and density. That said, homes on cul-de-sacs tend to have price premiums and create calmer streets. So, there is benefit, but just keep in mind it can affect the overall density.
As always, we welcome your comments, experiences, and questions below.