External wood claddings - performance criteria, driving rain and large-scale water penetration methods

In Norway, wood is widely used as an external cladding material. The performance requirements of a facade cladding can be divided into technical and aesthetic performance, where the technical performance is more distinct than the aesthetic one. Performance models for technical performance of wooden facades and deckings are under development and there is also ongoing research on the parameters that affect aesthetic performance. Wooden facades are recommended to be designed as a two-step tightening with a ventilated air gap and drainage opening on the back. The technical performance is mainly related to the ability of the construction to withstand wind-driven rain and the drying out potential of the chosen material and solutions.This work presents the results from a large-scale laboratory trial on three different wooden cladding solutions. The objective was to investigate the rain tightness of the different types of cladding, to detect water that penetrates the cladding and monitor the uptake of moisture, and the subsequent drying out. The trial showed that even at large amounts of wind-driven rain, only little water penetrated through the investigated cladding types. From a technical performance point of view, it is important to focus on an accurate mounting routine.