My mid 80's home, that I've lived in for 17 years has large gaps between the Alum siding and the chimney. The gaps look to be 1.5" to 2" in some places - I've attached a picture. I've not taken notice that these gaps have always been there or are getting worse. For moisture and rodent problems, these gaps need to be closed up. The gaps run for long distances on both sides of the chimnney where it meets the siding. Is there a DIY way to fix this for someone without any siding experience?