I am replacing old yellow pine T&G on a covered porch. The porch is over a finished basement which currently gets wet when it rains. I am planning to replace with an EPDM membrane and Tendura T&G. The difficulty is that the original 8″ thick knee wall style railings were installed after the flooring. The knee wall is 4″ off the floor. I am seeking a method of floor replacement that does not involve removing the railing system, which incidentally is covered with cedar shakes. Can anyone suggest a way fasten the PT plywood, membrane, 2×4 sleepers, and T&G without removing the railing or a cost effective alternative.

Thanks,
RSquared