Need your heads. I need to install a sliding door above a steel as in the picture, the finished floor level is at the top of the joists, i need to find a way in which to buildup from the steel inorder for the sliding door to sit at the right level (i need to be 70mm lower then the finished floor level.....currently at 220mm)i need to build up by 150mm from the steel. What's the best approach? -Timber I thought would decay over time. -Brick mortar? would it stick? or become lose. - whats normal practice. The steel is floating, there is a room below, so i may need to take in consideration a very small level of deflection/movement. What do you guys recommend. BTW the joist are being reinstalled.