A 45-year-old low-income senior housing tower in Midtown is slated to get a $12 million renovation starting in early 2019.

Cathedral Tower, at 80 E. Hancock St. east of Woodward Avenue, is the first affordable housing scheduled to be renovated using financing in part from Dan Gilbert's Bedrock LLC under an agreement approved by the city late last month.

The 236-unit building, constructed in 1972, is expected to get updated heating and cooling systems, new windows, upgraded kitchens and bathrooms and other improvements as part of the renovations to be completed in 2020, when an agreement to keep it as low-income is set to expire. Under the agreement, Cathedral Tower is to retain its affordable designation for another 30 years.

As part of the deal, the building will become affordable to those making 60 percent or less of the area median income rather than 80 percent or less, as it currently stands.

A joint-venture between MRK Partners Inc. and Fortus Partners is buying the property for an undisclosed price.

Arthur Jemison, the city's director of housing and revitalization, has said that as many as 2,000 affordable housing units in downtown, Midtown, Corktown and the New Center area are at risk of being converted to market-rate housing in the next five years.

"For equitable growth to happen in Detroit, we need to retain the residents who have stayed while attracting new neighbors. Preserving affordable housing in buildings like Cathedral Tower is a large part of that equation," he said in a statement.

"With this project, we are also taking the critical step of helping preserve existing affordable housing, ensuring that we don't take one step forward and two steps back by losing the existing affordable housing and long-time residents we have today," Dan Mullen, president of Detroit-based Bedrock, said in a statement.

Bedrock's agreement with the city calls for the development or preservation of 700 affordable housing units, based on being affordable to those making 80 percent or less of the area median income. That metric has been criticized because it is based on the Detroit-Warren-Livonia Metropolitan Statistical Area, which factors in household incomes from the suburbs, rather than just the city of Detroit, where the median household income is substantially lower.

In addition to the 236 Cathedral Tower units, Bedrock is also building 85 affordable units in its 28Grand development in Capitol Park and another 60 in its City Modern development in Brush Park. The remaining 319 units that are part of Bedrock's 700 affordable units have yet to be announced.

Cathedral Tower is owned by Bloomfield Township-based Princeton Enterprises LLC, according to CoStar Group Inc., a Washington, D.C.-based real estate information service.