My contractor that built my deck has also installed a self design underdeck roofing. His father,an engineer, designed it. Basically it consists of 2x2 furring strips nailed and caulked onto the inside of the floor joists and plastic panels caulked into place between them . Then exterior plywood was installed as a ceiling. The system is leaking in several places. They have attempted to repair it twice. Now they want to use caulk to fill the spaces between all the deck floor boards. Any thoughts?