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The prevalence of splitting in built-up roofing during recent years has prompted special studies to be undertaken by the Division of Building Research to determine the causes for these serious failures. The determination of certain engineering properties of the components used in built-up roofing and the complete membrane have received special attention. To determine these properties, a roller-coating technique was developed to prepare membranes and a special grip arrangement was constructed for the tensile studies. These studies were made at 75 F and at -20 F, using two rates of straining. The results emphasize the secondary role of the bitumen in the strength of the membrane. At both temperatures the felts contribute 80 to 90 per cent of the strength of the membrane, although the actual strengths increased by 70 to 250 per cent as the temperature changed from 75 F to -20 F. The small amount of creep and of notch sensitivity also serve to confirm the secondary role of the bitumen., Recent Research on Bituminous Materials

Le présent Digest traite des propriétés, des avantages et des inconvénients de nouveaux matériaux de couverture synthétiques, y compris les membranes préfabriquées appliquées en feuilles et les membranes appliquées sous forme liquide.

Concern has been expressed that increasing the amount of insulation to improve the thermal resistance of conventional roofing systems might adversely affect the performance of the membrane. Lower membrane temperatures caused by increased thermal resistance could induce higher stresses in the membrane, thus increasing the incidence of splitting failures. It is also feared that additional insulation could result in larger stresses in roofing membranes partially covered with snow. This Note evaluates the possible effects of increasing the amount of insulation on roofs.

Quality control of roofing and waterproofing membranes occurs at four distinct stages: 1) characterization of raw materials with respect to degree of purity required for an established formulation prior to production; 2) control of processing and manufacturing variables during production to permit necessary corrections before defective materials are produced; 3) testing and evaluation of finished products for conformity with the established standards or as agreed upon by the supplier and purchaser; where the latter is a large company or a government agency, compliance with a specification is usually required; 4) control and inspection of workmanship quality on the job site during the application in accordance with the architect's, engineer's or project manager's detailed job specification. Stage 3 has already been discussed in the author's previous publications. This paper highlights some of the quality control aspects and methods that could be implemented in stages 1, 2, and 4., 5th International Congress on Roofing and Waterproofing: 01 June 1983, Strasbourg, France

L'auteur étudie les toits à pente forte et à pente faible, les toits inondés et les toits-terrasses. On ne peut pas normalement construire un toit parfaitement plat; les fléchissements de la charpente entraînent inévitablement des pentes. Il est préférable de prévoir des pentes en vue de l'évacuation de l'eau. L'inclinaison minimale pour les parties principales du toit serait d'environ un quart de pouce à choque pied, mais une pente plus grande est préférable. Lorsque le mode de drainage est du genre tôle pliée, il importe de placer des dossiers à la jonction des surfaces plus grandes afin de détourner les eaux vers les drains. Lorsqu'un toit exige un drainage réglé ou un refroidissement par évaporation, une couverture inclinée présente moins de risques qu'un toit-terrasse. Dans les toits à membrane protégée, la membrane principale sur le plancher sous l'isolant et les matériaux d'aménagement devrait être à un angle, continue et scellée à la jonction de toutes les pénétrations.

In the last 20 years several new types of roofing material have been introduced to the construction industry, including various inorganic and organic materials and their combination, generally prefabricated. This paper deals only with single-ply membranes made from such materials as flexible polyvinyl chloride (PVC), elastomers, that is polyisobutylene (PIB), ethylene propylene diene monomer ( EPDM), hypalon (CSPE), and other rubber and rubber-like materials and reinforced modified bitumens. As there is need for criteria to facilitate appropriate selection and for specifications to ensure proper application, several test methods have been evaluated that assess physical, mechanical, and weathering properties of single-ply membranes. Some have been incorporated in the Standards of the Canadian General Standards Board (CGSB). Some of the more important tests include those for lap-joint performance, dimensional stability, water absorption, stress- strain properties, low-temperature flexibility, static and dynamic puncturing, load-twist, and the so called wheelbarrow test., Symposium on Single-Ply Roofing Technology: 24 June 1981, Detroit, MI, USA

New synthetic roofing materials, including prefabricated sheet-applied membranes and liquid-applied membranes, are described. Their properties, advantages and disadvantages are discussed.

Several hundred new roofing materials have become available in the past two decades. This paper describes the materials under three main generic classes: synthetic thermoplastics, thermosetting vulcanized elastomers, and polymer modified bitumens. Comparisons are made with conventional roofing materials and techniques, and some considerations necessary for selecting an appropriate roofing system are discussed.

Worldwide, there are more than 40 tests to assess the properties of nearly 400 conventional and new roofing products that exhibit wide ranges in a given property. New roofing materials can be divided into six distinctly different groups: 1. Hot applied rubberized asphalts; 2. Cold applied liquid membranes; 3. Prefabricated elastomeric sheeting; 4. Flexible polyvinyl chloride (PVC) membranes; 5. Prefabricated, reinforced, modified bituminous membranes; 6. Sprayed polyurethane with weather-resistant top coats. Each of these groups has its own specific characteristic properties that must be taken into consideration at the design stage. Test procedures were selected or, where necessary, developed to quantify properties before and after subjecting the materials to accelerated exposure conditions. This paper highlights the state of evaluating new roofing materials and describes test methods for this task. The concept and rationale of selecting tests for the different types of membranes and the tentative limits for various properties are discussed., Proceedings of Second International Symposium on Roofs and Roofing: 1981

A development study of test methods and criteria for evaluating new roofing materials is described: prefabricated polymeric and elastomeric sheets, prefabricated modified bituminous membranes, and liquid applied membranes. Results are summarized for a number of materials selected as typical of the three groups in order to illustrate the problems and the limitations associated with the different tests., Proceedings of the 1st International Conference on Durability of Building Materials and Components: 21 August 1978, Ottawa, Ont. Canada

Mineral aggregate surfacing is applied to built-up roofing to protect the top coating of bitumen from direct sunlight and to reflect solar radiation. It reduces the maximum surface temperature, the seasonal range of temperatures and the short-time fluctuations at the black surface. It thus inhibits weathering of the bitumen and the bituminous felts of the roofing membrane. There are some disadvantages to the use of mineral aggregate surfacing. Apart from the added dead weight, which must be carried by the deck and structure, the principal difficulty relates to inspection and maintenance. The aggregate surfacing hides defects and breaks in the membrane and must be removed to make repairs.

En vue de protéger le revêtement contre le rayonnement solaire directe et de réflichir la radiation solaire, on applique sur les toitures multicouches des revêtements en aggrégats minéraux. Ils provoquent une décroissance de la température superficielle maximale; ils réduissent aussi l'éventail des températures saisonnières et les fluctuations rapides de température sur la surface noire. Ils empêchent ainsi que les intempéries ne déteriorent le bitume et les feutres bitumineux du revêtement d'étanchéité de toiture. Le surfacage par agrégats minéraux présente certains désavantages. Si on met à part le poids mort supplémentaire que doivent supporter le tablier et la charpente du toit, la principale difficulté concerne l'inspection et l'entretien. Le surfacage par agrégats dissimule les défauts et solutions de continuité du revêtement d'étanchéite et l'agrégat doit naturellement être enlevé lorsqu'on exécute des réparations.

On étudie d'abord différents genres de toits. Il importe de noter que la fiabilité d'un toit à membrane protégée est liée à une seule membrane qui empêche le passage de la vapeur d' eau aussi bien que de l'eau. Cette membrane doit être continue et imperméable à l'eau dès la mise en place et tout au cours de sa durée de service. Elle se trouve dans un milieu favorable quant à la température et au climat et dure ordinairement plus longtemps que l'isolant, qui peut se détériorer considérablement avant que la membrane soit atteinte. On peut prolonger la durée de l'isolant par des mesures de drainage et d'évaporation de l'humidité quelle qu' en soit la source.

Steeply sloped roofs, low sloped roofs, flooded roofs and roof terraces discussed. A perfectly flat roof cannot be achieved in normal construction and slopes will inevitably develop owing to structural deflections. It is better to build in slopes to control water on a roof. The practicable minimum for main roof areas is about 1/4 inch per foot, and greater slope is desirable. Where drainage is achieved by a folded plate type of arrangement, crickets should be placed at the intersection of the larger slopes to direct water to the drains. When controlled flow drainage or evaporative cooling are required on roofs, a sloping roof produces a less hazardous condition than a flat roof. For protected membrane type roofs, the principal membrane at the deck below insulation and landscaping should be sloped, continuous and sealed round all penetrations.

In order to study the low temperature performance of asphalts, improvements have been made to the Institute of Petroleum Specification IP 80/53, for determining the brittle point of bituminous materials. A new procedure for preparing the coated plaques is proposed which enables a film of asphalt of known thickness to be prepared. The apparatus has been mechanized and the spring steel plaque replaced with a clear polyvester film. The brittle point unit is cooled at any desired rate using alcohol as the coolant. Studies have been made of effect of film thickness and rate of cooling upon the brittle point temperature. Study of the effect of overheating a dead-level roofing asphalt is shown to be one of the uses of the instrument., Proceedings of the Seventh Annual Conference of Canadian Asphalt Association: 1962-11

A modified Fraass brittle point test is used to study the hardening of asphalts that accompanies accelerated weathering. Four roofing asphalts exhibit variations in the initial brittle point temperature that may be related to the performance of the materials in an accelerated weathering test. The progressive hardening accompanying weathering is followed by an increase in the brittle point temperature.

Different roofing systems discussed in the opening paragraphs. It must be realized that the performance of a protected membrane system is related to a single membrane that serves as both air vapour barrier and water barrier. It must be continuous and waterproof from installation throughout its service life. It is in a favourable environment in relation to temperature and weather and will usually outlast the insulation, which can largely deteriorate before the membrane will be affected. The life of insulation can be extended by designs that allow for drainage and evaporation of moisture from all sources.

The investigation involved the application of ASTM Method D 1866-64 by subjecting individual pieces of aggregate to an ultraviolet light source. Using the same light source and the same method of photograhic interpretation but using graded aggregate layers, it was noted that unreasonable layer thicknesses would be required to prevent penetration of light through void spaces. The method was further modified by replacing the photographic interpretation with a phototube to obtain a quantitative measure of transmitted light. Aggregate types and thicknesses influenced phototube current and consequent voltage drops were measured by a sensitive voltmeter. Results show that only a small amount of ultraviolet light is transmitted through thicknesses normally used in roofing application with an aproximate 0.03 per cent difference between white marble and gravel. Results suggest that the advantage of white aggregate in reducing surface temperature may outweigh any disadvantages from its translucency.

The load-strain properties of several bituminous membranes when tested in tension are examined and the effect of temperature on the breaking load, load-strain modulus, and breaking strain is considered. The shear properties of the bitumens used as adhesives in the production of the membranes are examined at temperatures from -15 F (-26 C) to 32 F (0 C) at a rate of shear of 0.21 per min. The observed transition in the shear modulus of the asphaltic material at 0 F (-18 C) is found to coincide with the glass transition temperature of this material. The development of a critical- thickness concept is described, and it is suggested that the performance of roofing membranes under deformation may be controlled by the load-strain properties of the membrane and the shear properties of the adhesive.