A system includes a plurality of roofing shingles installed on a roof deck. Each of the roofing shingles includes first and second ends, first and second edges, a head lap, a reveal portion, a first side lap at the first end, and a second side lap at the second end. The second side lap includes a first surface, which has an adhesive. The first side lap of a first one of the roofing shingles overlays and is attached to the second side lap of a second one of the roofing shingles to form a sealed portion between the head lap of the first one of the roofing shingles and the head lap of the second one of the roofing shingles.