 The original building was shorter in length and contained only 4 retorts but foundations for later extensions were included and soon used as the building was extended.The small rear section plus the first connected division of the building were part of this extension with the divide visible by a slight change in brick colour.Inside, the coal was transported to the top level where it was deposited in a long hopper at the top level of the building (which also contains the conveyor drive and water tank).