Expansion joint missing, preventing new tiles from cracking

[Mike_I]

I removed the old failing tiles, discovering in the process that there is no expansion joint between cantilever concrete deck and pool shell. Crack runs the entire length around 20x40 pool. Any creative solutions to install new tiles without them cracking right away? Replacing the deck is not in the cards due to cost. I was thinking about cleaning the crack, building up the pool shell up to the deck but not touching it and then sticking a backer rod or foam in between before tiles go up. Any ideas on what that material should be? Any idea of a better way to solve the problem?
As a side note, the pool is not leaking except that crack by the skimmer, but that should be an easy fix.
Thanks

 

[ajw22]

Expansion Joints and Coping - Further Reading

www.troublefreepool.com

A “decoupling” expansion joint should extend across the entire width of the top of the bond beam to allow the deck to move independent of the pool shell. This joint can be created with a 4mm plastic sheet or 2 layers of roofing felt underlayment.

If your deck is sitting on the bond beam you will not have an expansion joint and things will crack again.

 

[Mike_I]

Thank you, that was one of the diagrams that helped me understand that I am missing the expansion joint. Regarding the material, where would someone find 4mm plastic? Or did you mean 4mil? I see there are 24x36 4mm Corrugated Plastic Sheets for Lawn Signs maybe I can try that. Since 40+year old deck is in place I only have access to the front of it and was hoping to minimize the cracking of the tiles by cutting in about 1" deep into the space where the joint is supposed to be and just applying it to that section. That is before the tiles go up

 

[ajw22]

Yeah, 4 mil.

If you do not completely uncouple the deck from the bond beam you will not accomplish anything.

Cutting in 1 inch is not adequate.