Construction will begin this month on a $36 million senior housing complex at 811 Lexington Avenue on the site of a former parking lot in the Bedford-Stuyvesant neighborhood of Brooklyn. Developed by IMPACCT Brooklyn, the four-story building will provide 63 apartments reserved for low-income seniors, who will also receive rental subsidies. Twenty of the units will be reserved for seniors at risk for homelessness. The development will also include a dedicated apartment for a live-in superintendent, a community room, and a roof-level recreation room that opens onto a planned green roof and garden.