You'd also have to look at the coefficient of expansion of the structure, beit wood or metal. PVC expands/contracts about 6x greater than concrete or steel and about 20x more than wood. Humidity changes in a wood structure may far exceed thermal expansion of the structure or the PVC, and should also be taken into account.
0.0000380 %/F, PVC
0.0000060 %/F, concrete (varies by type)
0.0000065 %/F, Steel
0.0000020 %/F, Wood (varies by type)
0.5000000 %/% moisture for Fir
352.44 requires an expansion fitting if this is going to be more than 1/4".
[This message has been edited by SteveFehr (edited 10-29-2006).]
