The Problem of achieving weathertight joints

The penetration of rain into a building is an age-old problem. A study of past and present building methods shows that there have been two basic approaches to the design of walls and joints. One is to attempt to eliminate all openings that might let water enter the construction, both in the masonry walls and in the fenestration; the other is to shed the water by using overlapping units, such as shingles, siding and thatch. These approaches are still used today. The various attempts to seal exterior wall surfaces have never been completely satisfactory. This is easily seen by the use of cornices, belt courses, mortar and stucco finishes, interior finishes for gaskets and cavity wall construction to improve the performance of walls designed on the basis of this principle. Wall design using overlapping units has proved effective in preventing rain penetration. In some cases in which wind-blown rain is particularly heavy, overlapping units, such as facing on masonry walls, was even used. Owing to the positive results obtained with overlapping units, this method is commonly used to limit rain penetration through the roofs of various types of buildings. With the objective of achieving weathertight joints, it is essential to fully understand all functional requirements, the various physical phenomena influencing joint performance and the close interdependence of all these factors.L'infiltration de la pluie dans le b\ue2timent est un probl\ue8me qui date de la plus haute antiquit\ue9. Une \ue9tude des m\ue9thodes actuelles et pass\ue9es de la construction d\ue9montre que, fondamentalement, il n'y a eu que deux concepts dans la planification des murs et des joints. Dans un cas, on a tent\ue9 d'\ue9liminer tous les passages accessibles \ue0 l'eau tant dans les murs de maconnerie que dans la f\ue9nestration. Dans l'autre, on a \ue9tabli la d\ue9perdition d'eau au moyen du chevauchement d'\ue9l\ue9ments tels que le bardeau, le parement \ue0 recouvrement et la chaume. Ces concepts sont encore employ\ue9 s de nos jours. Les divers essais de scellement des surfaces ext\ue9rieures des b\ue2timents n'ont jamais \ue9t\ue9 tout \ue0 fait satisfaisants. On peut facilement la constater \ue0 l' usage des corniches, cha\ueenes, enduits de mortier ou stucs, finis int\ue9rieurs sur profil\ue9s et l'usage de cavit\ue9s comme moyens d'am\ue9liorer le comportement des murs concus selon ce concept. Par ailleurs, la planification selon le concept de chevauchement des \ue9l\ue9ments s'est av\ue9r\ue9e avantageuse pour pr\ue9 venir l'infiltration de la pluie. Dans certains cas o\uf9 les pluies chass\ue9es sont particuli\ue8rement s\ue9v\ue8res, on a m\ueame employ\ue9 des \ue9l\ue9ments de chevauchement comme parement \ue0 des murs de maconnerie. A cause des r\ue9sultats heureux obtenus selon le concept de chevauchement, cette m\ue9thode est commun\ue9 ment employ\ue9e pour limiter l'infiltration de la pluie par les toitures de divers genres d'edifices. Dans le but d' obtenir des joints \ue9tanches aux intemp\ue9ries, il est essentiel de bien comprendre toutes les exigences fonctionnelles, les divers ph\ue9nom\ue8nes physiques rattach\ue9s au comportement des joints ainsi que l'intime interd\ue9pendance de tous ces facteurs.Peer reviewed: NoNRC publication: Ye