rain

Reports natural exposure test on vertical joints in open-jointed rain screen cladding. Describes test rig and gives results of water penetration tests. Gives design recommendations for screens.

Discusses some problems of providing weathertight joints between window and wall. Mentions sealing failures, condensation, frame defects and poor dpc detailing as important reasons for water penetration around windows. Refers to some principles of weather protection. Makes recommendations for the design of window-to-wall joints.

Reports tests using a natural exposure rig on a number of designs of horizontal and vertical joints employing labyrinths to separate the air and water entering the joint. Results obtained under a limited range of conditions show that it is possible, with suitable designs, to prevent penetration of water without necessarily making a joint airtight. Puts forward a number of potential applications, including a prototype window.

Known principles for the prevention of rain penetration and air leakage are not being applied in practice. States that rain penetration requires the simultaneous presence of water, openings and a force ; the two-stage weathertightening or "open rain screen" separates the control of these factors and allows the production of a weathertight joint under practical conditions. Outlines the causes of air infiltration and gives brief case histories to illustrate the serious problems that can arise from air leakage.

Gives the results of measurements of wind and driving rain carried out over a 1-year period on an 18-storey block of flats, and compares these results with calculated and model scale data. The in-situ measurements indicate that the pressure differences between various locations on a facade, exposed to rain are much smaller than the calculated values, and also pressure differences due to wind at a window between the inside and outside are much lower than the theoretical values.