The main factor that may weaken the stability of the roof structure is dampness. On its negative impact it is particularly exposed rafter framing, which deform under impact of water. Therefore is important roof protection against getting in  water into its internal structure.

Typically, investors during the construction of the roof attach great importance both for building materials, as well as careful execution. Unfortunately, later very often they forget about the survey, and any minor defects  commission outsource cheaper and often non-professional roofing companies. This is a big mistake,

Can I apply spray foam insulation directly to the. The system of installing metal roofing over the trusses or over purlins is typical. It gets more complicated when you look at adding the foam into the equation. Limited Lifetime Warranty MAC Metal Sales Metal Roofing COVERAGE

A very important element that must be considered when the roof is projected, is ventilation, allowing drainage of excess dampness from under the roofing.