The phenomenon of creep causes the deflection of a wood beam under sus
tained loading to increase throughout time. Current design codes inclu
de provisions to account for the time-dependent deflections of wood me
mbers in bending, but these guidelines have been based, to a large ext
ent, on past performance and engineering judgment only. Previous relia
bility studies for wood have not explicitly considered creep effects,
and consequently, questions as to the true limit-state exceedence prob
abilities associated with serviceability design procedures remain unan
swered. In this paper, the effect of creep deformations on the reliabi
lity of single dimension-lumber wood beams is examined. A stochastic v
iscoelastic stress-strain relationship is used to model the time-depen
dent behavior of wood, and stochastic pulse process models are used to
account for the temporal variability of the loads. Reliability levels
associated with current serviceability design procedures are then det
ermined, and resistance factors that include creep effects are suggest
ed for use in a checking equation for load and resistance factor desig
n.