Zoning – lot coverage


Maximum lot coverage is a ratio of the land covered by the building to the open space on the lot. In our page 5.3-5 example, lots <30’ are permitted 50% coverage and all others are permitted 37.5%. It’s not given a letter or number in the outline, but it occurs just below setbacks. This sounds pretty innocuous but it really becomes a major determiner of permitted building volume because city lots are fairly small. This information is described in detail on page 13.1-42. Also, there are some key exceptions. Here’s how it works:
  1. Calculate the area of the first floor, including exterior walls, the existing building if there is one, and any new structures. This must be done in detail because the plan review engineers will be figuring it in detail as well.
  2. Add decks or balconies which overhang, but not roof overhangs.
  3. Add the front porch as a separate number.
  4. Add the garage and any accessory buildings.
  5. We get an exception for the front porch if there is one. A maximum of 400 sf. Subtract that.
  6. We get a 50% exception for a detached garage if it’s at least 15’ from the house. Subtract 50% of garage area.
  7. Normally, without considering other exceptions and details, we add all the above to see if it comes up to the permitted maximum coverage.
    1. For instance, if our lot is 37.5’ x 100’ = 4,688 sf. Then 37.5% of the total = 1,758sf. A typical house is around 1,000 sf and 50% of a 22×22 garage is 242sf, so we have an available coverage of 1758 – 1000 – 242 = 516sf. In this example, our addition could be 2 ½ stories high and approx. 20×25. It could also be one or two stories high but the coverage could not exceed 20×25 or some other shape with the same area.
    2. The same calculation would apply to a new house.
    3. Obviously, everything in the above is a variable, so if we want to maximize the area of new improvements, we’ll need to try some combinations. However, this maximum coverage is normally more than enough.
Please let me know if you have any questions regarding the above.

Steve Culbertson