Differences Between Townhouses, Apartments, Condos, Duplexes and ADUs

A townhouse, apartment, condo, duplex and adu all have something in common inthe fact that they are all residences. They provide a place for people to live. Where things get tricky in the construction and building code world is how they are constructed, what code book is used and where the place of ownership begins and ends.

Apartments might be the simplest of the bunch. Each apartment unit is part of a building or multiple buildings and those buildings are sitting on a single lot or piece of property owned by one person or a business group. Apartments are not sold off individually and they all move together as a whole.

Construction of apartments has some built-in safeguards to protect the residents and the building that may be different than some of the other options. I like to think of each apartment unit as one Lego and that Lego has to be protected from the other Legos and the hallways and breezeways that lead to that Lego. (Can you tell I have kids?!) Therefore, each wall and floor surrounding the apartment is protected by a fire rating. Additionally, the breezeways or hallways are protected by a fire rating to get people out in case of an emergency. These protections are usually accompanied by a fire sprinkler system as well.

Condos are not too far off from apartments with the exception that each unit is owned by a separate individual. They are built basically the same as apartments with maybe some adjustments on the fire rating requirements. Each individual owner has title to and owns the space within the walls of their condo while the hallways, common areas, property, etc. are owned by all and upkept through monthly or yearly dues. Basically, a condo is an apartment that you own and then you pay a monthly fee to access all of the amenities and keep the grounds clean.

In the state where I live, condos are not very popular by builders due to state regulations and litigation, but as a homeowner, I think a condo would be a great place to live if you don’t want to deal with yardwork and general maintenance.

A townhouse takes it one step further than a condo in that you own the ground your townhouse sits on. Townhouses are typically connected together on the sides but there are no residences above or below a town house. I like townhouses mostly for the ability to own the ground that the structure sits on and have a little more privacy. Some even come with a small yard as well! Usually, the property line runs right through the center of the separation walls and is called a zero-lot line.

Construction for a townhouse can be done in a few different ways but the basic idea is to protect your residence from your neighbors and vice versa. Contractors will be required to install a rated wall between each unit and keep all penetrations through the roof at least 4 feet from the zero-lot line. The rating requirement for the separation wall depends upon if the contractor decides to install fire sprinklers. Usually, a lower rated wall is required with sprinklers such as a 1-hour wall. If no sprinklers are installed, a 2-hour separation wall may be required or more.

Apartments, Condos and Townhouses are usually going to be built under the International Building Code. Depending on how tall the structure is, how many units, etc., it may pull from the International Residential Code but I can't remember the last time I saw it when out doing inspections.

A duplex is 2 residences connected by a common wall or floor. This common wall/floor has more forgiveness than a townhouse or condo would have. Though a fire separation is required (usually of 1 hour) like the others, the building code allows for some forgiveness in how that separation wall is constructed.

The great part about a duplex in the building code world is that it is governed under the International Residential Code. The IRC is generally more lenient than the IBC and provides clearer options for construction in my opinion.

A duplex does fall under the single structure and single lot development, meaning it's not like a townhouse where each unit owns its own property. A duplex is more like an apartment where one owner owns the entire structure and a single piece of property.

Accessory Dwelling Unit (ADU)

An accessory dwelling unit is a great way to create a separate living space within a single piece of property. Many times, a residential zoned lot will not allow for multi-family units such as duplexes, townhouses or apartments. A way to get around this zoning requirement is to install an ADU or accessory dwelling unit. Essentially it is adding another unit to your property without having to ask for a zoning variance or change. The biggest difference between an ADU or duplex/apartment is that an ADU must use the utilities and address designated for the primary residence. This means that the power bill can’t be divided and the unit is not allowed to have its own address. These dwelling units are also called mother-in-law suites - for good reason. As prices of housing goes up and families tend to stick together longer, an ADU is a very smart option.

Should you decide to install an ADU and get denied for whatever reason, you can try resubmitting your application as a remodel only and remove the oven/range. The only difference between having a man cave with a bar and fridge or having an actual separate dwelling unit is the range/oven. As an inspector, I have had multiple people get caught putting in an additional unit without a permit or it wasn’t allowed for some reason and all they had to do is remove the range/oven. Just an extra tip just in case!