Standard Practice for Calculating Design Value Treatment Adjustment Factors for Fire-Retardant-Treated Lumber

Importancia y uso:

5.1 Fire-retardant-treatments are used to reduce the flame-spread characteristics of wood. Chemicals and redrying conditions employed in treatments are known to modify the strength properties of the wood product being treated. This practice establishes the procedures for determining adjustment factors that account for the isolated effects of fire-retardant treatment on design properties of lumber. These effects are established relative to performance of untreated lumber.

5.2 The effect of fire-retardant treatments on the strength of lumber used in roof framing applications is time related. In this practice, the cumulative effect on strength of annual thermal loads from all temperature bins is increased 50 times to establish treatment adjustment factors for fire-retardant treated lumber roof framing.

5.3 The procedures of Test Method D5664 employ an elevated temperature intended to produce strength losses in a short period of time. Although the exposure is much more severe than that which occurs in an actual roof system, the chemical reactions that occur in the laboratory test are considered to be the same as those occurring over long periods of time in the field.

5.4 Treatment adjustment factors developed under this practice apply to lumber installed in accordance with construction practices recommended by the fire-retardant chemical manufacturer which include avoidance of direct wetting, precipitation or frequent condensation. Application of this practice is limited to roof applications with design consistent with 1.3.

Subcomité:

D07.07

Referida por:

D8223-19, D5664-17

Volúmen:

04.10

Número ICS:

13.220.50 (Fire-resistance of building materials and elements), 79.040 (Wood, sawlogs and sawn timber)

Palabras clave:

design values; fire-retardant; fire-retardant treatment; lumber; mechanical properties; strength property; thermal effects;