Tiny homes are having a moment. Social media is filled with both downsizing enthusiasts and people who build backyard ADUs (accessory dwelling units) to make a little money on Airbnb. You may have even thought about building one yourself. Perhaps you have an old shed out back, or a nice plot of free yard space.

Sprucing up an existing structure sounds appealing, but is it a good idea? If you’re planning on sleeping there, or renting it out, there are tons of legal and safety considerations to keep in mind. For backyard workshops and she-sheds, you have more flexibility. Below, we talked to Kathryn Linea Rund, a designer and expert in land use and code compliance, to help you decide how to manage your backyard space.

Tiny Home vs. ADU: What’s the Difference?

First, let’s clear up some terminology. What’s the difference between a tiny home and an ADU? Can you use the terms interchangeably? Sometimes, Rund says. It really depends on the location, and who you ask.

What is a tiny home?

For two short little words, “tiny home” can mean different things to different people, Rund says. “Many people believe that a tiny home is on wheels and a chassis, like their affordable predecessor before them, the single wide trailer.” Others go by square footage, with a cutoff of 200 square feet. Oregon, where Rund lives, defines the term as “structures designed to provide low-cost or minimally sized housing options for consumers.”

What is an ADU?

Accessory dwelling units are a little more self-explanatory, Rund says. An ADU is “an accessory dwelling to the main dwelling of the property.” It’s a zoning term, with strict legal implications. While tiny homes can be the only home on a piece of land, an ADU by definition cannot. “This would be a completely different structure and residence from the existing residential structure and dwelling,” Rund says.

In other words: “A tiny home can be an ADU, and an ADU can be a tiny home, but not all ADUs are tiny homes, and not all tiny homes are ADUs,” Rund says.

Adding an ADU: What to Consider

Judging by the number of TV shows and YouTube stars out there talking up the ADU/tiny home movement, it may be tempting to throw a coat of paint on your shed, install some solar lights and call it a day. And that’s fine if you just want a chill backyard space to do crafts or relax and read.

But if you’re looking to build a lasting investment, doing your homework is important. That starts with zoning. “Zoning is essential when considering adding an ADU,” Rund says. “Every state, county, and city is different.” Here are the major zoning implications Rund recommends you consider before jumping in:

Permitting

“Depending on the zoning, you may be allowed to place an ADU outright,” Rund says. Other areas may only allow ADU under what’s called a “conditional use permit,” which is basically an exception to the zoning law. Some places don’t allow ADUs at all. “The purpose of the zones really governs what the property can be used for,” Rund says, so it’s important to check with your city planning and permitting office.

Footprint requirements

“Footprint requirements in the different zones can be problematic for developing an ADU,” Rund says. “Most of the time, land use codes will regulate the amount of development and open space on a piece of property using two tactics, setbacks and lot coverage.”

  • Setbacks create a “bubble of non-buildable space around the inside perimeter of the property,” Rund says. “Structures are not allowed to encroach into this space, thus, you can limit the building size, relative to the property lines.”
  • Lot coverage requirements set a maximum percentage of the property that can have residential structures. This is usually between 30% and 60%, Rund says, more for higher density zoning. This “naturally limits the size of your dwelling.”

Zone density

Rund says zone density controls the look and feel of a neighborhood. “Lower density zoning usually has a larger dwelling minimum size,” such as 1,000 square feet for the ground floor. As the density rises, the dwelling can be smaller. “It is not uncommon to see minimum limits bottom out at 500 square feet,” Rund says, eliminating any chance of “true tiny homes.”

Parking and other considerations

Are you considering driving an Airstream trailer into your backyard and hanging up a shingle? Again, these things are regulated. “If the home is on a trailer, they are considered RVs, and are banned from being used as a permanent dwelling in many city codes,” Rund says. Cities limit where you can place them, and they’re not adding value since they’re not considered real property.

“Other considerations are the parking requirements per dwelling,” Rund says. Cities often require hard surface driveways, and have carport and garage requirements when people develop a new residence on their property.

Can I Convert My Shed into an AD?U

Rund advises against it. “I would not recommend converting a shed into a tiny home for multiple reasons, but mostly because it is unsafe and not saving you any money,” Rund says. Homes are built “with specific fire-rated construction so that they burn without failing for several hours, so that people have time to wake up and escape,” Rund says. “Sheds are not built to this standard.”

“You could buy a shed and bring it up to code with full renovations, but it won’t save you any money, and it will only be more problematic than designing an actual tiny home,” Rund says.

About the Expert

Kathryn Linea Rund is the Strategic Design and Development Advisor at Real Estate Bees. She’s an expert in land use and code compliance, CAD/BIM and residential and sustainable design. She’s also the owner of Kathryn Linea Rund Design Studios of Sweet Home, Oregon.