The purpose of this thesis was to clarify the structure and moisture technical functions of a hybrid insulated expanded clay roofing. The objective was also to examine the production phase of the structure and methods to ensure functioning and quality roof structure.

The hybrid insulated expanded clay roof is a structure where mineral wool or expanded polystyrene insulation is installed in between the vapour barrier and the expanded clay insulation. In the space between the vapour barrier and extra insulation there is almost no air ventilation at all, so any moisture entering the structure in the construction phase or due to roof damage will not be dried by convection. Structure is commonly used, because the insulation specifications have been tightened over the years, so a structure without extra insulation is too thick in many cases.

In the production phase of the structure, it is very important to pay attention to moisture control and quality control at the worksite. In most cases the best way to ensure the quality of the result for the structure is to make meticulous pre-planning for the work. It is practically impossible to prevent any moisture from entering the structure and for that reason it is important to maximize the air ventilation between the vapour barrier and insulation with structural solutions such as leaving little gaps between the insulation panels and fill them with expanded clay and using grooved insulation panels. This is important also because even if the construction phase is done correctly with minimal moisture in the structure, it is always possible that the moisture gets into the structure from waterproofing or vapour barrier damage.

This study also covered good methods for quality and moisture control at the worksite. Knowing the methods for quality and moisture control are key factors to achieve a correctly working, high quality roofing.