After drying out the furnace and following its shrinkage, particularly vertical shrinkage, we were concerned that the tunnel did not provide enough clearance for the fire. We decided to move it upwards by about 1.5" so it was just below the Phoenix plaque.

The first job was to make a better foundation for the tunnel to sit on, which we did by building up the level behind the lower stokehole bricks with tiles and daub.

After marking the new height of the the tunnel on the furnace wall we removed the daub using a hammer and wood chisel, exposing a small portion of ceramic fibre blanket in the process.

We repaired and smoothed over the surface with daub (not photographed) and replaced the tunnel on two 1" layers of ceramic fibre blanket. The weight of the tunnel compressed the fibre so the the tunnel sat at the correct height.