yes it does.All building materials expand and contract, but not at the same rate. For example, upvc materials expand and contract at a different rate than wooden materials.
Dazzer, January 2010
Only in hot conditions - when cold it contracts
You can sometimes hear it cracking as it moves
The coefficient of linear expansion of PVC-u is about...
0.00006 per ºC which is about 5 times that of steel and 2½ that of aluminium
