Some of the state’s most exclusive neighborhoods could be effectively exempt from a proposal to allow duplexes, triplexes, fourplexes in single-family zones across the state.

House Bill 2001, sponsored by House Speaker Tina Kotek, D-Portland, would allow the higher-density plexes and “cottage clusters” on any single-family lot in cities with 10,000 or more residents. The goal is to increase the supply of rental homes and drive down rents — and in the process open desirable neighborhoods, with amenities such as good schools and parks, to more people.

But restrictions recorded on property deeds when the neighborhoods were developed — even some from a century ago — sometimes prohibit the construction of anything other than single-family houses.

“In the residential areas, they show up with some frequency,” said Alan Brickley, a longtime Portland real estate attorney.

It’s difficult to say how many neighborhoods might be affected. Deed covenants regulating the number of housing units are common in newer large-scale developments, but also in older planned communities platted by a single developer. The restrictions themselves, however, are buried deep in property records. Cities don’t generally track them.

But they’ve left residents of neighborhoods without such restrictions wary that they could bear an outsized share of the density created under the policy, if it passed.

“It would force the developers into the older areas like where I live,” said Bill Aspergren, a co-chair of the South University neighborhood in Eugene. “If you go into the newer areas, nobody’s going to be able to put a quad in there even if you could find room for it.”

The covenants are effectively private contracts that could open homeowners who build duplexes on their property to lawsuits from their neighbors. More likely, the higher density homes would never get built.

Kotek suggested lawmakers could act to render the covenants unenforceable.

“Deed restrictions that prohibit more housing choices undermine the intent of House Bill 2001," she said in a statement. "We need to make sure that, going forward, deed restrictions do not further the exclusion that this bill is trying to address.”

The Oregon Legislature recently acted to nullify deed restrictions already on the books. In 2017, lawmakers barred homeowners associations or developers of planned communities from prohibiting the installation of rooftop solar panels and declared previous restrictions void.

That law has never been tested in court, however, and government interference in agreements between private parties can face a high legal bar.

Unconstitutional deed restrictions — namely those that excluded people from neighborhoods based on their race — have been nullified by the courts. The state in 2017 also created a process for removing those unenforceable restrictions from property records.

The issue also could affect density plans in cities like Portland, where the city’s Residential Infill Plan calls for more multi-unit houses in established neighborhoods. A spokeswoman said the city’s Planning Bureau was aware of the potential issue but not clear how widespread it might be.

House Bill 2001 already faces opposition from neighborhood groups, many that say it will bring crowding and hurt property values.

And cities, including Portland, have said they’re uncomfortable with the aggressive timeline set out in the bill, which gives cities until December 2020 to write code allowing for the new housing types.

-- Elliot Njus

enjus@oregonian.com; 503-294-5034; @enjus

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