How do I get rid of black mold on beams of attic?

Black mold is nothing to play around with. Sometimes a pro is best. A mixture of 50/50 bleach and water to wash it off. Rinse well and let dry. Then a wash of 50/50 vinegar and water to kill the mold spores. Do not mix bleach and water together. Do this if it's not that serious.

https://restorationmasterfinder.com/restoration/what-kills-mold-bleach-vs-vinegar/

https://www.servicemaster-restoration-cleaning.com/2017/03/30/mold-myths/

https://www.servicemasterrestore.com/blog/mold-damage/mold-myths-will-vinegar-kill-mold/

If it is just starting to grow, you can handle yourself. If more than what vinegar will handle, call in the pros, mold is nothing to fool with. You could unknowingly spread to the rest of your home.

Hi Diana - There are several ways to get rid of mold, but most importantly, you need to address the root cause to keep it from returning. This article focuses on the bathroom, but is an overall great article that covers methods of how to remove mold, if bleach is safe to use, and how to prevent it from coming back. Hope this helps! Hugs, Holly

https://pinkfortitude.com/mold-in-the-shower/

Naomi’s has good advice. I would recommend you wear a respirator or you could end up very sick.