Residential Floor Systems: Wood I-Joist Creep Behavior

Abstract

A creep study was undertaken to characterize the creep response of a wood I-joist framed and oriented strand board (OSB) sheathed floor system under typical residential in-service loads (e.g., gravity and environmental). The study examined one full-scale floor system constructed of composite wood I-joists and OSB sheathing for 508 days of sustained uniformly distributed loads equivalent to the design dead load, 0.48 kPa (10 psf), plus 25% of the design live load, 0.48 kPa (10 psf). The creep deflection of the system fluctuated with changes in environmental condition (e.g., temperature and relative humidity) but virtually stabilized after 168 days of loading regardless of variation in environmental conditions. The average of the individual floor joist ratios of total creep deflection to initial deflection was 1.66 at 508 days for the floor system. The observed ratio is greater than would be applied in standard United States or most international design practices.