They re installed before the tile is laid on the roof and may serve more than one purpose.
Metal roof without battens.
The key in most cases is having a properly vented attic beneath that.
Can a metal roof be installed over my existing shingles without the use of battens.
This is a bit of a complicated question.
While roof battens are most commonly made of metal or wood they can be made of other materials like plastic or composite there are several different types of batten some combine two materials to get the needed affect.
It sounds like the metal panels you re installing probably have a great deal of contact with the underlayment unless they are installed on top of battens.
This creates a thermal break which is very similar to a vertically seamed metal roof installed on battens.
In most cases there is nothing about a metal roof that increases the need for ventilation beyond what is needed for an asphalt shingle roof.
This is the case with most vertical seam products.
Whereas many older metal roofs or metal roofs on larger buildings have been successfully installed over battens rather than solid decking it is the clear preference for residential applications that metal roofing always be installed over solid decking to avoid dangerous and damaging condensation issues.
For example elevated battens are standard wood battens that have a block of plastic in some cases wood attached to the underside to elevate.
Roof battens are thin strips of material that may be made of wood plastic or metal.
This great question comes from edward c a homeowner who plans to have a new metal roof installed over the aging existing shingles on his single story home.
These products usually have an integral airspace or an insulated cavity between the metal and the roof deck.
Note that you can have a metal roof.
As a great option to the expense and bother of battens there are concealed fastener metal shingles shakes and tiles available.
Thanks edward for allowing me to share our correspondence on this frequently asked question.
Types of roof batten systems.