Blockwork sitting on top of I beam. Iv tried filling the void with timbers at every 300-400 covering with building paper/roofing felt and covering again with riblathe. All joints crossed at least 400mm. We have tried filling the void with cement board aswell doing thin coat with mesh and topped with sand+cement but always after a few month's hairline cracks appear at the 2 ends where the I beam sits on the concrete pad and some cracks where the timbers were inserted behind the felt or...
Blockwork against I beam
Blockwork against I beam