Need Expansion Joint for underdeck shed

[DLausche]

I would like to build a 10' x 12' storage under my deck for storing the mowers and snowblowers, etc. Already have a floating slab under the deck. The deck also has an underdeck rain diverter system so it is nice and dry under there. I'd like to construct 2x4 walls and side it to match the house (vinyl siding). The only thing I can't figure out is some type of expansion joint to use between the top of the 2x4 wall and the deck joists. I think I should plan for at least 1. 5" of movement. Measured during the middle of winter and then this spring and noted that there was about 1. 25" of frost heave during the winter. I've been looking for some type of Z or W fold vinyl strip that I could use to fill a gap between the shed wall and the bottom of the joists. Anybody know of a long type of expansion joint that a guy could use for such a purpose?



Thanks

-Deon