The couple announced their engagement last August after just a month of dating and Chad, 38, admitted feelings developed while working on music for Avril's upcoming fifth album.
He told KIIS FM DJ Ryan Seacrest: ''When you're sitting there across from someone singing into the microphone and you're singing a love song, you start to develop feelings for them. And it just kind of blossomed into this kind of thing and the next thing you know ... we started dating.''
Avril, 28, added: ''We met - in the studio - and I was really excited to work with him because he's also a musician.
''[We] wrote a bunch of songs together, became really good friends and now we have a wedding.''
And the couple knew straight away they wanted to spend the rest of their lives together.
Avril - who was previously married to Sum 41 rocker Deryck Whibley - recalled: ''We started dating and the next day he was like, 'You know I'm gonna marry you.' And I said, 'I know.' It was one of those things that we just knew.''