Green Day rocker BILLY JOE ARMSTRONG has put music to one side to join forces with a New Orleans charity helping people left homeless by Hurricane Katrina. The singer has been volunteering in the Louisiana city, rebuilding houses destroyed by the August 2005 storm. And Armstrong isn't afraid to get his hands dirty - as snaps posted on the band's website show. In a message posted there this week (12Apr07) he explains the work he has been doing, "Today we worked on the upper 9th ward. I had to do some upside down hammering technique but we managed to get the job done. We felt a great sense of accomplishment when we finished." Hurricane Katrina is a cause close to Green Day's hearts - the band teamed up with U2 to record charity track The Saints Are Coming.