EWPAA Structural Plywood and LVL Design Manual - Engineered ...

ClosurePlywood Thickness for:Douglas fir(USA) (mm)ComparableCHH Radiata Pine (mm)10 6.4 7 1215 9.5 12 1220 12.7 15 1725 15.9 17 2130 19 19 25Rating(Minutes)RecommendedCHH Radiata Pine (mm)TABLE 16.12: Fire Resistance Level for Structural Stability for Non-load Bearing PlywoodThe main aim of this revision is to provide the first time designer of fire resistant structures with somebackground information and pointers to aid in the plotting of a path through the process.Also, it is hoped it provides the experienced practitioner with relevant updated fire resistant design dataregarding plywood and LVL. This should allow their use, with confidence, in a wide range of applications.The ramifications of a fire, be it localised in a kitchen, bedroom, etc. or from a bushfire, can be horrendous. Itis, therefore imperative, the designer provides the occupants with every chance of survival.16.9 Resistance to DecayThe durability of structural laminated wood veneer products is dependent on the durability of theadhesive used to bond the veneers and the durability of the timber veneers themselves.16.9.1 Durability of the AdhesiveThe Type A phenolic bond, used in structural plywood manufactured to AS/NZS 2269 and structural LVLmanufactured to AS/NZS 4357, will not creep or break-down in applications involving long-termstructural performance and/or extreme long-term exposure to weather, wet or damp conditions. It is adurable, permanent bond.The EWPAA tests bond quality of samples obtained from every production shift ofEWPAA manufacturing members. The bond quality test for a Type A bond involves a72 hour boil of the plywood or LVL sample (or 6 hours steaming at 200 kPa pressure).The specimen is then chiselled apart along each glueline and the amount of wood fibrefailure evaluated. The quality of the bond is determined from the amount of wood fibrefailure present. More than 50% wood fibre retention by the adhesive after chisellingindicates the bond is stronger than the surrounding wood fibre, i.e. a good bond hasbeen achieved. Less than 50% wood fibre retention would indicate a failed bond.16.9.2 Durability of the Timber VeneersStructural plywood and LVL are predominantly wood products and in addition to the adhesive durability,the durability of the timber veneers must be considered for each specified application. The majority ofstructural plywood and LVL manufactured in Australia and New Zealand is made from radiata, slash orhoop pine timber species. These pine species have an expected service life of less than 5 years whenused in exposed applications in contact with the ground, if they are not preservative treated orotherwise protected, (based on CSIRO durability classifications). Their expected service life when not inground contact but fully exposed to the weather would be much longer.As a general rule, structural plywood and LVL used in exposed application will need to be preservativetreated and surface finished to meet the exposure hazard and required service life. Generally, the mainhazards for which structural plywood and structural LVL durability needs to be considered are:● decay253