If the tin roof sits on top of another material such as wood then you can get a case of wood rot.
Steel roof condensation problems.
Warm wet air rises and meets the cold roof and cools.
The lower the pitch of a metal shed roof and also the deeper the corrugations the worse the problem of metal roof sweating.
Metal gets cold faster than other items so condensation begins on metal first.
Although condensation in roofs may not seem like a serious problem it actually is.
Essentially condensation occurs at night when the temperature inside a building is warmer than outside.
This video shows what a significant condensation problem can look like.
It can lead to roof leaks even if rain has not occurred for several days.
Metal roof condensation especially with a tin roof can cause serious problems when the metal sweats or rainwater collects under the tin panels.
Changes to the structure s original form that puts tension on or moves the panels.
As it cools it can t hold as much moisture.
When this happens the tin roof can rust and even warp.
Having vents in all elevations of the shed is an effective way of minimising metal roof sweating.
In the case of the timber trusses and purlins they will rot and eventually lose their stability.
Picture a cloud of moisture floating overhead between the rafters.
Condensation on metal roofs can be a problem once the weather starts to get cold.
That excess moisture ends up as drops of condensation on the roof.
Inadequate space allotted for thermal expanding and contracting of the panels.
The key to getting condensation to evaporate is air flow.
This applies to both the timber and steel trusses.
It is the leading cause of the deterioration of trusses.
Condensation happens when moisture filled air contacts anything that is below the dew point temperature.