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Housing, Trees and Zoning Changes

Updated: Oct 30, 2020

The City of Atlanta is working hard on another update to our zoning ordinance. It’s another round of Quick Fixes to address smaller tweaks to areas that should not be overly controversial. However, you never know what is going to trigger resistance and outrage when discussing modifications to property rights.

One of the surprising areas of contention is a push to strike the provision allowing accessory dwelling units (ADUs) in the R-4 zoning category. A lot of the resistance to this change is coming from various groups that think this new provision will result in the clear cutting of a lot of Atlanta’s amazing tree canopy.

We are going to break down some of these zoning terms to hopefully shed some light on things…

R-4 zoning (including R-4A) is the single-family zoning category that includes medium sized lots, usually in older, more walkable neighborhoods, but also occurring in a range of in-town neighborhoods across the city. For context, the next zoning down, R-3, is also single-family and requires a minimum lot size of 18,000 SF and 100’ of frontage. R-5 is the next zoning category denser than R-4. It tends to be nearer to MARTA stations on the East/West line, has a minimum lot size of 7,500 SF, and allows two-family housing (duplexes).

All single-family zoning categories (R-1 through R-5) currently allow for Guest Houses. What is a Guest House and how is it different than an ADU? Great question. A Guest House is a detached structure located behind or beside the main house, has enclosed living space, but it is expressly prohibited from providing long-term housing and having a stove. However, the zoning code makes an exception and does allow long-term habitation for “servants and watchmen”. Essentially, Guest Houses are great for housing your domestic staff, or for generating a lot of income via AirBnB. They can’t, however, legally play an effective role in addressing our current housing crisis in Atlanta.

Guest Houses are limited in size relative to the size of the main house. The bigger the main house, the bigger a Guest House you are allowed to build. This makes sense considering how many more servants (zoning term, not ours) you would need to house to take care of your larger estate. This rule penalizes small houses that would like to do a Guest House, as theirs must be much smaller. One would expect they would need less servants, though….

Accessory Dwelling Units differ from Guest Houses in a few key ways. They are legally allowed to be used for long-term occupation, and can be rented out as such. They are also allowed to have stoves. Therefore, they can play an important and effective role in providing much needed affordable housing. An ADU is also allowed to be up to 750 SF total, regardless of the size of the main house, but cannot be any bigger.

Any R-4 lot that might want to have a Guest House or ADU must comply with the overall lot coverage requirements (50% for R-4, 55% for R-4A). This means that above that the lot cannot have impervious surfaces on it. Buildings, driveways, and sidewalks count as this impervious surface – Guest Houses and ADUs included. Both Guest Houses and ADUs are further limited to covering no more than 25% of a lot’s rear yard.

So, allowing ADUs seems like a reasonable way to add some long-term housing to our city. What’s not to like? Since allowing ADUs sounds like a new form of development, it must be inherently bad and must be stopped. We understand zoning is obtuse and convoluted, and most people have no idea that they could already build a Guest House, and that ADUs might sound new and dangerous. But really, the only difference is that ADUs allow long-term housing options.

Concerns over the city’s tree canopy are valid; our canopy makes us unique, enhances quality of urban life, and provides countless ecological benefits. Concerns over ADUs potentially destroying the city’s tree canopy are misguided. Guest houses will still be allowed in all single-family zoning categories regardless of the quick fixes. Blocking ADUs simply means blocking long-term housing choices in single-family districts (unless, of course, you are a servant or a watchman).

If we want to consider ourselves an inclusive and caring community, we are going to need to embrace the reality that we need to find ways to provide more housing for more neighbors. Allowing ADUs in more places is one important small step forward for housing that we must support. We also need to accept that the harder we make it for people to affordably live in the city, the more we encourage sprawl and all of its unfortunate consequences. If this article resonates with you in Atlanta, we STRONGLY encourage you to call or email you councilperson with your thoughts as soon as possible. Their contact information can be found at:

Image: ADU designed and built by ATL ADU CO on an R-5 lot. No trees were harmed in the making of this ADU.

Some additional ADU information from some of our previous posts can be found below:


Primarily, the size of an ADU is limited to 750 SF, while Guest Houses are limited to 30% of the main house on the lot. ADUs are legally allowed to have full cooking facilities, whereas Guest Houses can have an amazing wet bar, but not a built-in stove. And while ADUs are permitted to house long-term renters, Guest Houses are not (unless you are a Watchman or a Servant – really!)

ADUs count towards the allowable buildable square footage (your FAR – Floor Area Ratio) of your lot, but Guest houses do not. This means that if you want to build an ADU, you would not be allowed to build as big of a house. Most existing houses don’t max out their square footage, so this is typically not an issue.


1) ADUs cannot be sold separately from the main house (hence the term accessory).

2) The total number of units on the property cannot exceed two, including the ADU.

3) Except in the case of home occupations, no accessory use shall be permitted or allowed for a commercial venture.

4) The unit must be 750 SF or less.

5) There is no minimum lot size required but you cannot create a new substandard lot of record in the city.

6) No direct access road is necessary.

7) There is no needed parking space designated for the ADU.

Originally posted by Eric Bethany for KWA and ATL ADU CO

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