What am I doing wrong? (trying to make a patio)

Hi y'all! I know I'm really not the best with building and wanted to add a patio to this house. However, there's a flat roof/awning that showed up after I made it and I don't know how to delete it.

It's creating a shadow over the patio and there doesn't seem to be a good reason for why it's there since there are no pillars to hold up or anything.

Could someone help me figure out what's up and how to fix it? The picture of my issue is below. Thank you all!