The prelaying of urea formaldehyde particleboard floors, as a working platform before the erection of the walls, has been practiced in New Zealand for the past 12 years. Approximately 80 percent of all new houses are constructed in this manner. Little is published about the extent of deterioration of particleboard that occurs during the exposure to the weather before houses are closed in. This paper reports the results of changes in physical and mechanical properties of particleboard exposed to the weather for periods of up to 6 months. The changes were measured both before and after the particleboard had been sanded back to a clean surface. After 3 months weathering and subsequent sanding, the particleboard tested met standard criteria for bending strength. Lack of a suitable surface for clear finishing may determine the amount of weathering the flooring can be subjected to before the houses are closed in.