Assessment of Longitudinal Shrinkage and Swelling Using the APA and ASTM Methods


  • Trevor G. Jones
  • Ian G. Simpson
  • Jonathan J. Harrington


APA, ASTM, longitudinal shrinkage, radiata pine, swelling


The APA and ASTM methods of measuring longitudinal shrinkage and swelling were evaluated and compared using radiata pine coupons with a wide range of wood properties and different operators. The two methods gave different measurements of longitudinal shrinkage and swelling as a result of differences in the location of the measurement points, and the ability to correct for out-of-plane distortion. The APA method gave more precise measurements from the use of inserted brass eyelets and the correction of out-of-plane distortion with a vacuum table. The measurements were not affected by wood type or operator. The ASTM method was found to be sensitive to the condition of the transverse surface at the measurement point and to the presence of drying distortion. The measurements varied in response to wood type and operator. The results indicate the APA method is more precise for measuring longitudinal shrinkage and swelling when measurements are made in series along boards and cants.


APA test method (2001) P-1. Linear expansion and thickness swell measured from oven-dry or 50% relative humidity to vacuum-pressure soak. APA PRP-108 Performance standards and qualification policy for structural-use panels. Pp. 43-44. APA-The Engineered Wood Association.nASTM standard (1999) D1037-96a, Sections 107-110, Linear variation with change in moisture content. Annual Book of ASTM Standards, Volume 04.10: 154-156.nLittell RC, Milliken GA, Stroup WW, Wolfinger RD (1996) SAS System for Mixed Models. SAS Institute Inc., Cary, NC 633 Pp.nNordström J-EP, Johansson I (1995) End-grain glue-joint strength. Part 2: The microstructure of machined end-grain surfaces of spruce timber. Holz Roh-Werkst 53:38.nOehlert GW (1992) A note on the delta method. Am Stat 46(1):27-29.nSAS Institute Inc (2000) SAS/STAT User's Guide. Version 8, Volumes 1, 2, and 3. SAS Institute Inc., Cary, NC.n






Research Contributions