• Medical ADU
    After being craned over the roof of the existing home at right, this medical ADU was fastened to a prepared pier foundation. The two units will later be connected by a deck.

Over the past few years, a growing number of municipalities have adopted zoning rules that allow homeowners to build small backyard residential structures, typically described in code language as Accessory Dwelling Units, or ADUs. More colloquially known as "granny flats," they're a favorite of urban planners who see them as a way to increase suburban housing densities by allowing seniors to move in near adult children or other family members.

As they age, however, many seniors will find themselves in need of more care than a conventional ADU and those nearby family members may be able to provide. With that in mind, several US companies are developing specialized ADUs designed to serve as stand-alone assisted living units or nursing home rooms.

Getting medical. Among the pioneers of such "medicalized" granny flats is the Blacksburg, Virginia-based company N2Care, which manufactures a 300-square-foot unit it calls the MEDCottage. A recent Washington Post article detailed the experiences of one D.C.-area family in installing such a unit to care for an elderly parent.

N2Care presiden Ken Dupin notes that the prefabricated MedCottage includes built-in utilities for oxygen eqipment and a range of medical devices, including systems to continuously monitor the occupant's vital signs. Also standard is special-low impact flooring designed to minimize injury in the event of a fall—a feature the company likes to demonstrate by dropping a raw egg onto it without damage from a height of seven feet.

The standard 12x24 MEDCottage unit actually measures a couple of inches less in width, enabling it to be transported easily by truck from one of two manufacturing facilities in Virginia. Once at the site, the unit can be craned onto a prepared pier foundation, avoiding damage to existing fences and landscaping. The basic model currently cost about $85,000, not including delivery and installation. A larger 48' module is also available, which includes space for a live-in caregiver.

Housing by prescription. Are such units the wave of the future for tens of millions of aging baby boomers nationwide? That may depend on the responsiveness of state and municipal governments.

In Virginia, a 2010 state law guarantees homeowners the right to install temporary medical ADUs even in jurisdictions where accessory units aren't ordinarily permitted, as long as certain conditions are met. The building permit is conditional on a pysician's prescription, and the ADU must stand in an "umbilical relationship" to the primary structure, with the electrical, water, and sewer connections tied into the existing system rather than separately metered connections. The Virginia law also applies only to factory-built structures—a so-called "bubba provision" meant to prevent the proliferation of substandard site-built units.

Waiting for a case. Ken Dupin acknowledges that there's scant prospect of passing a similar law in all 49 remaining states anytime soon. But there is, he says, another way: Should a local government anywhere in the US refuse to grant a building permit for a MEDCottage installation, the company expects to request a ruling from the US Attorney General's office on the applicability of the federal Americans with Disabilities Act to medical ADUs in general.

In practice, Dupin says, such a unit is no different than a wheelchair ramp on the outside of a historic building. "You can't be denied a permit because the local government doesn't like the way it looks," he says. "When the right case comes along, we're prepared to make that argument."