Abstract: Many new roofing systems appear to have considerable advantages over conventional bituminous roofing, but most have not yet been extensively field tested. Gravel as a protective covering has been dispensed with entirely in the newer systems, so that inspection and maintenance during and after application is greatly simplified. Imperfections and damage can easily be seen and repaired. Reflective and decorative coatings are easily applied. Most systems are light in weight and have much greater elasticity than conventional systems. Promoters, however, in their enthusiasm tend to forget or ignore some of the factors that cause failure such as building movement, trapped moisture and poor workmanship. These factors still exist with the new as well as the old systems. These systems also introduce new factors such as dependence on thin layers of adhesive to provide water-tightness at narrow joints, and bridging characteristics of fluid systems over rough surfaces and joints, as well as the need to adhere strictly to recommended materials and procedures. Despite any new problems that may arise, it is certain that the percentage of roofing using these new systems will increase during the next decade.
Subject: Roofing; bituminous roofings; elastomers (rubber); tarred felts; Roofs; Moisture performance; Couvertures : New Roofing Systems
Canadian Building Digest; no. CBD-49, ISSN: 0008-3097, Publication date: 1964-01
Abstract: This digest demonstrates the application of the principles and considerations discussed in previous digests in the design of exterior walls. An insulated masonry wall is used as an example and is compared with a modified design to illustrate possible improvements.
Abstract: Sound insulation between occupancies in office buildings forms the subject of this Digest. Some general cautionary remarks were made in a previous discussion of noise transmission in buildings (CBD 10); it is proposed here to develop office problems in more detail, with special attention to partitions.
Abstract: The calculation of temperature and heat flow through the walls, windows and roof of a building is the first step in preventing problems arising from thermal stresses and condensation. This Digest is intended to supplement CBD 4, CBD 5, and CBD 36 by discussing the various modes of heat transfer that occur at the surfaces of buildings, pointing out the complications that must be considered in some cases.
Abstract: Deflections in horizontal flexural members do occur and are influenced by several mechanisms, some of which have cumulative effect. With the contemporary practice of using higher working stresses and more slender members, deflections are greater than those that occurred with past construction methods. With finishing and cladding materials being installed to close tolerances, excessive deflections cannot be tolerated unless they are adequately predicted and allowed for. In many cases it may be necessary to redesign structural spanning members to reduce the total ultimate deflection to suit associated finishes, partitions and walls. These points all indicate that deflections due to elastic strain, creep, shrinkage, temperature and moisture changes, load characteristics and form of structure must be considered, especially when the design deviates from practices that have proved satisfactory.
Abstract: Glass is successful in meeting its requirements as an element in an exterior wall. The joint between the glazing unit and the window sash or frame, however, is vulnerable because of the many requirements it must fulfil. The most common expressions of failure are glass breakage and rain and air leakage. Successful glazing requires an understanding of all the factors that contribute to failures and a knowledge of the properties of the materials to be used. Knowledge of the requirements of each component of the joint detail is also essential. The demands upon each component of the joint can be minimized by good design.
Abstract: Many buildings become disfigured soon after their completion from cracking of glass and finishes, spalling of surfaces, failure of mastic joints, and occasionally, the breaking loose of a material from those surrounding it. The mechanisms responsible for such failures are usually associated with deformations in materials due to moisture content and temperature changes or chemical action. This Digest attempts to show the need for greater consideration in design of the deformations and induced stresses that can and do occur in restrained building materials from temperature and moisture changes.
Abstract: In selecting double windows for a particular application it is most desirable to have information regarding their inside surface temperature characteristics. The choice of windows may be influenced by the inside relative humidity conditions desired or anticipated and the amount of condensation that can be tolerated. The thermal limitations of double windows must be recognized in establishing building humidity. For some applications and window constructions it is necessary to determine the surface temperature characteristics by individual tests. For general-purpose rating for thermal performance the test conditions must be standardized, particularly the surrounding construction and the surface heat exchange conditions.
Abstract: Large areas of glass in any facade that receives direct sunshine require shading if people must work near the windows. The best arrangement, from the point of view of solar control, is to design the building with the glass facing north; the second best arrangement is to have it facing south and to provide both a canopy shade and a venetian blind. When windows must face east or west, the summer heat gain can be minimized by placing a slat type shade on the outside, or if this is impractical, by using double glazing with a blind between the panes.
Abstract: The requirements of window glass as an element in an exterior wall are determined by the differences in the environments being separated. With proper consideration of the characteristics of glass available, selection and design to satisfy these requirements can be achieved.