External Thermal Insulation Composite Systems (ETICS) with Rendering are widely used in both rehabilitation and new building projects, even in areas with harsh climates such as the western regions of Norway. However, we have seen extensive cases of defects involving such systems. This paper presents a comprehensive review of Norwegian experiences regarding the durability of ETICS on walls. The presented results are based on building research conducted by SINTEF 61 as well as 30 accelerated climatic laboratory experiments over the last 25 years on similar façade systems. These systems generally perform satisfactorily if thoroughly designed and carefully erected. However, according to the survey, the systems are not very robust. Even minor errors in design techniques and/or craftsmanship can lead to rendering defects. The investigations clearly show that ETICS is particularly vulnerable when exposed to severe driving rain conditions. ETICS provides only a single-stage protection against wind and precipitation and do not dry effectively after being wetted. Hence, the resultant cracks and other rendering weaknesses could be disastrous, enabling moisture to penetrate into the thermal insulation and the wall behind. In areas with heavy driving rain, we recommend façade solutions erected in accordance with the principle of two-stage tightening rather than ETICS.

Alongside well-researched themes such as water and moisture, the service life and function of masonry veneers are often compromised by precipitation combined with poor design considerations, execution, and selection of materials. Little research has been carried out on the subject of the impact of mortar consistency on masonry's resistance to driving rain. Water-repellent (WR) impregnation is typically considered a quick fix when problems occur. Wall-panels of 1 m 2 built with different flow table values for the mortar have been tested in a driving rain chamber, where both time-lapse videos and the measuring of penetrated water are used to evaluate performance. Subsequently, the panels were impregnated with the most common types of WR products and re-tested. The analysis shows that changing the mortar mix from dry to wet can decrease the penetration of driving rain by a factor of ten. The test results presented in this article show that mortar with low water content gives a porous interfacial transition zone (ITZ), thereby increasing the rate of water penetration. The tested WRs are found to be ineffective in increasing masonry's resistance to high pressure driving rain. The results, combined with what is already known about WR treatments on masonry, call for careful consideration before applying such treatment. This proves especially true in countries with much driving rain followed by frequent freeze-thaw cycles.