A wall fastener assembly for use with a building wall system, with the wall fastener assembly including a fastener and an elongated, semi-rigid seal member. The fastener includes a shaft and a head, with the fastener configured to be secured to the wall system. The seal member includes opposed first and second ends, and a center bore that extends along the length of the seal member and is configured to receive the shaft of fastener. When the fastener is secured to the wall system the first end of the seal member is configured to compress against a portion of the wall system to form a first seal and the opposite second end of the seal member is configured to form a second seal to thereby seal the wall fastener assembly against the wall system.