Exacting Standards

After we had discovered that 5% lime behaves very differently to 4% lime, we began improving our standards. To establish the water content of the soil, we first weighed a sample and then saturated it in alcohol. This we set alight and stirred while it burnt itself out and in the process evaporated off all the moisture. We then weighed the sample again and the difference was the water content. The next step was to weigh a standard wheelbarrow of soil and using a bit of simple arithmetic, we calculated the dry mass of a standard wheelbarrow of soil. We then recalculated the mass of the lime based on the dry mass of the soil. This required us to drop the amount of lime added and now we are operating at far more exacting standards. To what extent this will improve the shrinkage of the soil is anyone's guess but at least we now know that we have minimised the possibility of stabilisation cracks.

Our window boxes have improved significantly with experience. The amount of kicking is now minimal and the openings are perfectly straight - whereas before we always had small kick somewhere on the face. Now using lots of wedges and bracing, the end panels remain true. On the window openings, we have been flying blind and living in hope to some extent. We know the window sizes, but there was a degree of uncertainty of the windows and their dimensions that would finally arrive from China. Well they did arrive yesterday and there were many panels and each one was surprisingly heavy. I ended up taking two panels to the site and we were pleasantly surprised. Johan was simply grateful that they were actually made to size and fitted comfortably into the spaces we had created for them. This made his day. I was really pleased with the colour and the neat internal blinds that gracefully slide between the double glazing. So between showing off the fact that they fit and that they have fancy little features, there was relief all around on another gamble that had paid off handsomely.



The steel reinforcing for the roof arrived and now needs to be assembled. We finally decided to go with a rib and block roof structure, where the ribs are steel channels and the blocks are made of polystyrene. Due to the significant spans and the fact that we are going to have a heavy (planted) roof, the roof needs to be unusually strong. As a consequence, we have quite a bit of reinforcing. To avoid using steel reinforcing mesh, we have decided on a fibre additive that is added to the concrete that equally boosts the strength. Trevor the concrete specialist advised us to use waterproof concrete. He said that the torch on bitumen product always fails - not that it is a poor product, but it is only as good as the application, and it is the application that always leads to problems later. So we have asked for waterproof concrete which is stronger and is guaranteed by the supplier. Presuming that it is 100% effective, I am now revisiting how I will lay the planted roof. Before I was planning to have a waterproof layer, then a drainage layer with special plastic drainage cups, then a geotech fabric and on top of that the planting medium. Now with a genuinely waterproofed roof that has a 7.5degree fall for drainage, I'm inclined to place a course gravel layer directly onto the concrete slab. Over this can go the geotech fabric and then above this a layer of riversand that will aid in the filtration of the rainwater and finally the planting medium. This will be significantly cheaper, longer lasting and probably as equally effective.

In the meantime, builder's holiday begins on the 11th December and everything (despite the recession) closes down for a month. We were hoping to get the roof up by then but were concerned that we would not make it. We are still concerned about this timeframe however we have now found a subcontractor who specialises in the erection of these roofs and has all the tools to do it. He is confident that it can be done in time but this is obviously reliant on the electrician and plumber installing their services in time. The benefit of this is significant - concrete takes 28 days to reach its full strength and after the concrete is poured, it must remain supported for around 3 weeks before the props can be removed. By letting the roof cure over the holiday, we are saving a significant amount of time.

Finally we have begun the trenching for all the plumbing and electrical reticulation. We've managed not to confuse the plumber with all the groundwater drainage and the rainwater, greywater and blackwater reticulation needs. It seems that houses were build like this in a previous era and the plumber adapted fairly easily to the requirements when he managed to relate the layout to one that exists in his mental archives.