Under the deal, Portsmouth would rent its new city hall building from Armada Hoffler for 20 years for at least $2.16 million per year, with an annual rental rate increase of 2 percent. It would also pay for new parking spaces there — under the cheaper of two options offered by the company, the city would pay $18.4 million for 670 spaces. The building and parking would go on the site of the city's County Street parking garage, which would be demolished.