Construction guide
Why tin roofs "rain" indoors, and how membranes stop it
Condensation under metal roofs is one of the most common building complaints in warm, humid climates.
On clear nights a metal roof cools fast. Warm, moist indoor air meets the cold sheet and condenses, then drips onto ceilings and insulation.
A breathable underlay catches that moisture and lets vapour escape through ventilation, instead of trapping it like polythene does. The result is drier ceilings, longer-lasting insulation and less rust.
