St. Charles officials recently altered the affordable housing requirement for developers to account for the fluctuating market. The city’s inclusionary housing ordinance dictates how many units in a development must be affordable if a developer wants to build homes in the city. State law says 10 percent of a city’s housing stock must be considered affordable. City Planner Matthew O’Rourke said the state uses a formula to determine what is affordable each year. For St. Charles, a home listed at $199,500 or less for a family of four is considered affordable, he said. The city now has a “buffer,” and aims to keep affordable housing at 13.75 percent or above, O’Rourke said, to make sure levels don’t go too close to the state standard.