Today we rammed our last wall on the house. It was not as exciting as we had hoped but perhaps we have passed the novelty stage of exposing rammed earth walls to the elements and the whole process is now becoming fairly routine. Nevertheless, it was a milestone and we are generally very pleased with the overall result. We are fairly regularly reminded of what we've achieved by the awestruck expressions of any new visitor. So are convinced that we have managed to do something fairly special - although the road has been fairly long.
We have learnt many lessons and still don't have all the answers to some of the questions. The biggest outstanding question is how we should properly 'cure' a newly rammed wall to prevent it cracking. Some walls cracked, others didn't. One wall began cracking and then stopped after a few inches while another cracked severely from the top to the bottom. The reduction in lime content certainly improved matters, but how much is hard to say. The final solution will be a combination of several things including (and probably most importantly), the drying rate. However, to put things in perspective, we have rammed 19 panels one of which cracked badly, one cracked slightly (a 4 inch hairline crack), one has cracked in one of our expansion cuts and is not visible and the rest have been fine.The wall in the above picture sprung a small hairline crack very quickly but we began wetting it regularly and this seemed to make it disappear. Now we can't find the original crack and we continue to keep it fully hydrated.
Instead of wrapping the walls in plastic, we have now placed a thin layer of sponge on top of the wall held down with two fibre cement barge boards that protect the chamfered edges. We then covered the entire wall with shade netting and this we soak twice a day. The sponge retains quite a bit of water and the shade netting lets our water reach the wall yet provides it some protection against the full force of the spray. This is one of our theories and it has worked so far. All the cracks begin at the top of the wall and work their way down. The top of the wall obviously dries out the quickest, with three faces exposed to the worst effects of the sun and the wind. By keeping it wet, it remains fairly plastic giving the rest of the wall time to dry out slowly and develop in strength. By the time the top is allowed to dry out, most of the shrinkage has taken place without a crack developing. However this is still a theory and perhaps I will have a definitive answer by the time we complete our next project - the utility building.
We treated our other end-wall similarly. For several days we saturated the wall but kept it covered with plastic rather than shade netting. Finally we sprayed it with the newly recommended sealant. It sucked up around 50 litres of sealant over three days. When we now wet it, it still absorbes water but retains a permanent wet look - which is a much darker shade. We are unsure whether the wet look is due to locked in moisture or whether it is the effect of the sealant. However it has not yet cracked (it may still do so) but we are unsure of how it will develop. Obviously we would like all the walls to look more or less the same colour and we wait patiently while it decides what it is going to do. I would obviously prefer the darker shade than an unsightly crack and time will tell.We attempted a patch job on the wall that had the severe crack.
We cut out the 1.2m panel where the crack had developed and then rammed a new panel in its place. The difficulty is trying to get the coloured lines to flow seamlessly into one another which would help obsure the fact it was a patch. We managed to do an acceptable job, however we expect some shrinkage and hopefully this will manifest itself as a vertical crack at the joint - something we can hopefully hide beneath an 'expansion joint'.
Something else that we have learnt over these past few weeks is the effect of rain. The walls have withstood unbelievable amounts of rain. We have had two storms where 50mm of rain was dropped on them in a few hours. We have also had 3 days of solid light rain which flooded the rain gauge - so was at least 100mm. And the walls have survived this bearing the full brunt of these deluges. But not wishing to tempt fate, we have recently covered just the top of the walls with plastic held down with bricks. However, our nicely sieved sand did get wet despite it being covered. The winds were often too much for our plastic to bear and either ripped it or removed it. 
This significantly raised the moisture content of the soil, which made it sticky. When mixed in the pan mixer, this created a high number of small round balls which when dropped into the form always sought the outside edge/face of the wall. This is also a result of how the soil is spread in the form as when it's spread, the balls of soil all roll to the lowest points which are invariably against the shutterboard. Consequently during the wet phase, many of the walls have an unusually high percentage of roughly finished surfaces as in the picture above. The individual balls are clearly visible. This can be compared to the finish we were after in the second picture, which has the line through it. However, even the rough finish adds character to the house and certainly every wall has a story to tell.Other than the concerns about existing and future cracks, the walls do look stunning.
To remind us that progress is being made, the rib and block roof arrived today and just in time for the builders holiday! We have been through several roof designs and finally decided on the steel rib and polystyrene block arrangement. This reduced the weight of the roof and also improves the insulation qualities. Since this roof will be the last thing standing in this town, the polystyrene is likely to remain in place for several hundred years so I am quite OK with this decision - for the benefit of my conscience that has this product high on its list of things never to use. At least it is not one of those single use polystyrene coffee cups that fill up landfill sites!
The food forest is also beginning to establish itself. The water collects behind the swale just as Geoff Lawtons Permaculture video shows it should. The trees have been well watered and some have been the unfortunate victims of drowning - the ground is so saturated and high in clay that the trees just seem to spend their time swimming. The rest have survived almost tornado speed winds, had their leaves blown off and are now recovering back to where they should be. 
Some have decided not to grow leaves at all this year in view of the weather. The marula's are just not performing at all. They look like planted sticks with name tags attached to them. The fluted milkwoods are battling with the winds. One has lost all of its leaves and the others look tired from fighting. The acacia's are fine as are most of the citrus. Several pawpaw's have drowned but one or two seem to be returning from the dead. The rest are sprouting nicely. The bees are having a fantastic time and a fairly strong hive has recently taken residence on top of one of our test walls. It's obviously the karma of the wall that so energises them! The birds are obviously happy with the trees and a local fiscal shrike has taken to impaling his food on the thorns of some exhausted plant.Below is a video slideshow showing the disassembly of the shutterboard - the daily reveal!
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