Problem w/ new windows - when to pay contractor
We just got the old windows in our 85-year-old house replaced with new Jeld-wens. The windows themselves look great and the contractor did an excellent job, even correcting the 'work' of a previous contractor, but many of the sashes, especially upper ones, seem too tight. Contractor agrees there is an issue and has notified supplier (Home Depot) and Jeld-wen. Contractor is asking for payment in full (gave 1/2 down at beginning of project), but I'm hesitant to pay this off.
My thinking is that although the quality issues with the windows aren't directly the contractor's fault, the job is not yet completed. I'm leaning toward offering the contractor 80% of the balance, with the remaining paid immediately upon resolution of the quality issues. Is this strategy right or am I missing something here?