Here the inside of the completed rock wall portion of the composting chambers can be seen. The rear portion will be completed using ferrocement from the ground up, making it quicker and easier to create usable openings for the access doors through which the finished compost will be removed. The "Odjob" brand mixing drum (black with green lid) used to mix mortar and concrete batches can be seen in the background, just left of center.
The metal mesh armature for the ferrocement portions of the composting chambers is under construction. The skeleton, consisting of 3/8" rebar and nine gauge galvanized wire, is being covered with one layer of expanded metal lath on the outside. Two layers of one inch galvanized hexagonal mesh ("poultry netting," "chicken wire") will be added on the inside. The two layers of hex mesh will be offset so that the holes in each layer are criss-crossed by the wires of the other layer. All three layers are attached to the skeleton and each other using small twists of 20- or 22-gauge galvanized wire.
This view from the rear of the chambers shows the complete metal mesh armature in place and ready for plastering, including the center divider that separates the two composting chambers. The concrete thresholds at the bottom of the door openings were formed using simple wooden forms, and were poured after the bottom ends of the vertical door edge rebar pieces were put in place and plumbed. Vertical rebar that extends above the top edge of the armature will be cut off later.
This view from the front shows some more details of the finished metal mesh armature for the ferrocement portion of the structure. The vent pipe fitting for one chamber can be seen at left. It is a standard 45-degree bend ABS DWV (Drain Waste Vent) pipe fitting that has been inserted through the finished mesh armature. The male end is pushed through a snugly fitting hole in the mesh from the inside to the outside. The ridge or shoulder forming the female end sits against the inside of the mesh. The fitting is then simply plastered in place.
Here is a view of the East Wing after plastering. The vent pipe described above can now be more easily seen as it protrudes out of the ferrocement wall near the top edge. The darker color around the door edges and top edge of the wall indicates that these areas have been more recently plastered than the chamber walls - the plaster is still a bit wet there. I find it easiest to do the edges after the rest of the structure has been plastered. The irregular meeting of rock wall and ferrocement wall can be seen to the right of the door opening. These areas took a bit of extra patience and care, both when applying the metal mesh and when plastering.