Exterior Wall Enclosure

An exterior wall enclosure is part of the envelope covering the vertical planes at the perimeter a building. It divides the interior and exterior environments providing protection to building occupants and contents.  A well designed and constructed exterior wall enclosure will stop moisture from entering the building, keep the building insulated and can prevent the spread of fire between neighboring buildings. Exterior walls are also a major architectural feature and architects use a wide array of techniques and materials to meet an intended performance criterion while also providing unique aesthetics to a building’s facades.  The exterior wall enclosure can typically be divided into two main sub-systems: the exterior wall systems and fenestration systems.

Exterior wall systems are designed and constructed in a variety of forms and materials. Brick, stone, wood, composite materials, metal, concrete, concrete masonry units and stucco are all examples of materials commonly used. Traditional solid masonry wall construction, sometimes referred to as mass walls, have been used for millennia and are formed with multi-wythes of brick or stone. This type of wall relies heavily on the thickness of the masonry and mortar joints to resist stormwater. This system is largely considered antiquated, with modern cavity and barrier wall systems taking precedent. Cavity walls consist of an outer wall layer connected to an inner wall layer with an air gap cavity between. The cavity is used to manage rainwater that penetrates the outer wall by diverting it away from the inner wall. The air gap also provides thermal insulation, with the air acting as an insulating barrier between the inner and outer leaves. In modern construction, cavities are filled with rigid or mineral fiber insulation with further increases thermal performance. Barrier wall systems rely on the integrity of the outermost material to prevent rainwater from entering the wall assembly. This system can be in the form composite spandrel panels, curtain wall systems and exterior insulation and finishing systems (EIFS).

Fenestration systems refer to the presence of an opening in a building and typically relate to doors and glazed elements such as windows. The doors enable entry of vehicles, materials and people in and out of a building. Types of doors vary in design and purpose from single leaf swinging doors or rotating drum doors at pedestrian entrances, to large automated roll-up overhead doors at vehicle entrances. The glazed elements provide a weather barrier against the outside environment but also provide natural light transmission and can provide additional ventilation into the building. The glazed components can be in the form of windows or incorporated into the design of the exterior walls such as at storefront and curtain wall systems.

Due to the importance of the exterior wall enclosure as the first line of defense to protect the occupants and contents of the building, it is often considered a high priority component. Quite often there are common deficiencies in exterior wall enclosure design, construction, materials and maintenance. Owners often spend large amounts of money on exterior wall enclosures in the form of on-going maintenance and component replacement.  The exterior wall enclosure should be routinely inspected, especially during the due diligence stage of a property acquisition to avoid unforeseen costs.

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