APA S580 PDF

INTRODUCTION

Structural glued laminated timbers (glulam) bearing the APA EWS trademark are produced by members of APA – The Engineered Wood Association. These glulam timbers are manufactured to conform with ANSI Standard A190.1, American National Standard for Structural Glued Laminated Timber.(1)

Although glulam does not require preservative treatment for most uses, certain applications may present environmental conditions conducive to decay, insect or marine borer attack, such as the long-term or frequent presence of moisture (generally 20 percent or greater moisture content of the wood) accompanied by temperatures ranging from 50°F to 90°F. Decay slows at temperatures outside this range and virtually ceases at temperatures below 35°F or above 100°F.

Conditions conducive to decay or insect attack are typically controlled through recognized design principles and construction techniques, such as use of overhangs, flashings, ventilation and proper joint connection details. When these conditions cannot be avoided, glulam must be pressure-preservative-treated or a naturally durable wood species must be used. Examples of construction where such hazards may exist include direct exposure to weather, ground contact (including direct contact with concrete foundations and footings), contact with fresh water or sea water and exposure to excessive condensation.

Outdoor uses of preservative-treated glulam include bridges, utility structures, marine applications, highway noise barriers and decks. Indoor uses that may require pressure treatment include environments subject to high humidity or condensation such as indoor swimming pools or greenhouses, where moisture content of the wood may exceed 20 percent. Indoor applications, such as post-frame construction in some agricultural buildings, may also involve ground contact, and thus require preservative treatment for those members in contact with the ground.