The excavation of some Iron Age iron smelting furnaces near Wokingham for West Sussex Archaeology is a major current project. The furnaces have a wide flat floor, they are over a metre in diameter and have a broad arch with a large raking pit. They therefore have some morphological similarities with the later Roman domed furnaces of SE England.
The site has two furnaces sites. One was almost completely destroyed by a modern pit. The other has an early furnace that was demolished and filled with slag and the debris from its superstructure, with a replacement furnace constructed over it and just 0.5m further west, so that it was able to use the same raking pit and slag dumps. The two furnaces are aligned and bounded by short lengths of shallow ditch.
Update 17.8.14: Excavation of the first furnace showed that it had a similar form to its successor. The clay wall of the pit was vertical and horseshoe shaped in plan. The arch was effectively the entire width of the pit and defined externally by a pair of large furnace-bottom slag blocks, oriented vertically.