Image courtesy of Google Maps.

Boylston Properties wants to expand a 10-year-old boutique hotel near Boston’s North Station.

The firm bought the Kimpton Onyx Hotel for $46.7 million earlier this year.

According to a letter of intent filed with the Boston Planning & Development Agency, Boylston wants to build an 8-story, 77-room expansion with ground-floor retail on a 5,499-square-foot surface parking lot adjacent to the existing 155 Portland Street hotel.

The proposed expansion will top out just under 100 feet tall and contain 40,725 square feet of gross floor area. No new parking will be provided for the hotel, which will have 189 rooms with the addition.

The letter of intent states the project has been designed to be as-of-right from a zoning standpoint.