7 to 15 5 pounds per square inch at 50 percent deflection 2 compressive set 16 percent maximum of original thickness after 22 hours of loading and 24 hours of recovery 5 tear resistance 10 to 12 pounds per square inch in the machine direction 7 thermal stability 1 5 percent maximum shrinkage over a three hour period with no load at 180 degrees fahrenheit 9 thermal conductivity 0 25 btu per hour foot squared degrees fahrenheit per inch k factor at 7 degrees fahrenheit above the pad 11 is flooring 19 which is a series of boards including boards 21 23 and 25 the boards 21 23 and 25 are machined tongue and grooved end matched and assembled from contiguous and adjacent beech strips 27 and 29 the strips 27 and 29 are assembled at the longitudinal joint 31 by means of a jointer using a double dovetail and permanently glued using a polyvinyl acetate adhesive centrally located in the boards 21 23 and 25 a standard grade of beech is used and each board 21 23 and 25 is five and one sixth inches wide by twelve foot one and five eights inches long by seven eights of an inch thick the boards 21 23 and 25 weigh 3 28 pounds per square foot the.