The study focuses on the interaction of the complex wooden structure created between the double shell that covers the Chapel of the Tesoro di San Gennaro, part of the Cathedral of Naples. The work is part of a larger research that proposes to study the dome as a single system through a combination of methodologies involving limit analysis and reticular wooden structures. The theories used consider the principles of masonry structures (no-tension material) and the timber elements treated with elastic theory. The research aims to define the interaction between the two structural systems, starting from Heyman’s theories about curved masonry structures. The presence of two different materials determines a complex and inhomogeneous system in the static behaviour, highlighting the reasons that led to the construction of such a “forest” of solid chestnut wood. The actual operation of the whole artefact is evaluated considering that the timber structure supports the upper dome without burdening the lower one, having been built in favour of the stability of the elliptic upper dome. The research evaluates the variation of the structural behaviour of the actual system compared to the original design, which did not involve the wooden structure.