Can it be installed over my current roof?

In most cases, Yes!  

This not only allows us to keep from making the mess that most people associate with replacing an asphalt roof-no nails!-but also provides an extra layer of sound deadening that will keep your home more quiet.

*Building Codes may require the tear-off of shingles when more than one layer is present.  Make sure that your installer explains to you how your roof's current condition will affect the installation of your new metal roof!