Accessory Dwellings broken down

At the beginning of this process there was concern that a historic district would restrict density. To some restricting density sounded great, to others it seemed extremely detrimental. But what if we could have a historic district that enabled growth in the future but within the historic fabric of our neighborhood?

On Monday Sept 16, CPNO Membership voted to KEEP IN the regulation in the proposed Historic District to allow up to 2 ADUs per lot (currently 1 is allowed).

** Under Zoning 2.0 apartments within existing houses will also be considered ADUs.

Can my neighbor build a two story duplex ADU in their backyard?
Considering the various sizes of houses and lots, it is impossible to do an analysis of every property, however there is an easy way to calculate the max cumulative square footage of accessory buildings allowed on a given lot. All accessory structures combined are limited to 30% of the size (square footage) of the primary house and the cumulative total sf of the main house and accessory buildings is limited to 50% of the size of the lot (FAR). So: 
Max Accessory SF = .115 x (SF of Lot)
​

In addition, a few things to keep in mind are:

• Height of accessory structures is limited to 20 feet by zoning. 
• Max Lot Coverage of 50% includes all accessory structures, paving, decks, etc.
• Max FAR (square footage of interior space, on all levels) of 50% will still be the rule.
• Zoning Code governing ADUs in Atlanta will remain as is

EXAMPLES

1. SMALL LOT: For a 50x110 square foot lot on Sterling, the max total of all accessory buildings is 632.5 sf with a house of 2,117.5 sf. The current house on the lot is about 2,100 sf, so they could add an ADU that is no more than 630 sf (30%) or they could make an addition up to 650 sf to the single family home. This is CURRENTLY the case for this lot and that WOULD NOT CHANGE under a potential Candler Park Historic District. 
   ​What would change under the proposed HD? They could add 2 ADUs of 315 sf each instead of one at 630 sf.
2. MEDIUM LOT: Let’s take another example, a typically-sized 50x150-foot lot. The max square footage for buildings on this lot (FAR) is 3,750 sf, and the max square footage for accessory buildings combined is 862.5 sf, if the main house was 2,887 sf. If the main house was smaller, OR bigger, there would be less allowable square footage that the accessory buildings could be. A 2,000 sf house could not have a single ADU bigger than 600 sf, or 2 ADUs bigger than 300 sf each.
3. LARGE LOT: a 50x185-foot lot on Elmira could have a maximum accessory structure floor area of 1,064 sf, IF they had a house that was 3,561 sf and all other regs were met. The existing house is only 2,563 sf however, so they can currently build up to 769 sf of accessory building space (30% of the primary house). Again, the ONLY change in the proposed HD would be that they could divide that allowable square footage into 2 smaller ADUs if they wanted. If they think 384 sf dwellings is a good idea. 

How big is an ADU??
A tight one-bedroom apartment w a kitchen-living area and a bathroom could reasonably be 450-600 sf.
A studio could be as small as 350 sf. but 400 is more likely. Studio apartment ADU example.
These plans provide good examples.

Who lives in an ADU?
Rental income either long term or short term, multi-generational living, or an office/guest house.
Short term rentals (STRs ie Airbnbs) are governed by Atlanta's STR ordinance.