Hal, it is my understanding that a concrete deck will crack, reguardless as to what you do. The plastic strips are just a bigger 'control' joint. My source of this info is in the public domain, you can go to www.straightdope.com or go to a good library and read the book itself (he's published 5 and it's in one of them - sorry I can't recall which one the ? was in, but if I get the time - I'll look through my copies)