An exterior wallboard sheet includes a core having opposing first and second major surfaces. The core may include a monolithic body of aerated concrete. At least one water vapor-permeable, water-resistant face layer may be secured on at least one of the first and second major surfaces of the core. The water vapor-permeable, water-resistant face layer may include a microporous polymer layer. The microporous polymer layer may include a woven polypropylene fabric layer having a plurality of microperforations therein.