Most products can or must be installed on solid deck.
Metal roof strapping or not.
Very few must be installed on strapping.
However the problem would not have been completely solved unless you had also first installed vertical strapping from the eaves to the ridge so that water would have had channels to drain through.
Thanks for investigating metal.
There are two ways to do this put in firring nailing though nails are not used any more for this strips or purlins in steel frame construction on the roof to support it or place the metal roofing directly on a flat surface like foam insulation board or the roof sheathing with roof water barrier in the correct position in the layer.
600mm bent 100mm ron sammons strap is a lightweight restraint strap that can be used instead of a traditional heavy duty strap to provide lateral restraint of roof trusses rafters and joists tied to masonry and for vertical applications such as holding down the wall plate.
The best way to have prevented the problem would have been to install 15 or 30 felt which should always be installed under metal roofs regardless of the type.
Spacing of furring strips for metal roof when installing a metal roof over an existing roof insulate the spaces between the wood strips with rigid insulation to prevent condensation before.
The pre drilled holes allow various fixing points for horizontal and vertical application.
There are several things to consider when determining whether or not to have your new metal roof installed over battens.
1 some products can be installed on strapping.