Hello,
I was lurking this website after a exhausted google search about deck building stumbled to this website. Glad I found this website, have alot of questions, and welcome all constructive criticism or better alternatives. I have a double wide Mobile home with a back door approx 2' from ground level. I'm wanting to build a 18' wide X 12' deep, free standing deck with possible 6" x 6" post to support a gable roof. I had a brain storm of setting the deck post, beam joist, and rim joist on 16" x 16" concrete masonry units (CMU) buried below frost line. My first question is how close can I be to the septic tank and line without worrying about disturbing them from the elements of nature? In addition, how wide and deep does the concrete footing for my 16" X16" CMU have to be in order to avoid separation, cracking or blow out?

Thanks

 

Welcome to the forums!
Locally they want any structure to be 10' or more from the tank or drainfield. They aren't as strict when it comes to decks. IMO you'd be safe at 2'-3' away. The footer should go down to the frost line and that is dependent on where you live.