LAST BLAST BEFORE CHRISTMAS

Our final order from Ciolli Brothers Readymix, 12cu.m of 15MPa concrete for the 90mm thick ground floor slab, was due to arrive at 9am on Thursday 22 December 2011. So it was a bit of a scramble to get the damp proof sheeting and pre-cut underslab Isolite insulation in place before the arrival of the two concrete trucks. 

Laying the damp proof membrane

Placing the 40mm Isolite insulation over the damp proof membrane

 The concrete pour went ahead on time and without event, bar an apparent slight underestimation in the amount of concrete required. This was quickly remedied by the builders, who mixed up the required extra quantity of concrete by hand in no time, and wheelbarrowed it in place. By 11:30am the slab was complete.

The slab pour begins...

Mixing a little extra concrete by hand

The completed 90mm thick ground floor slab

Work was then begun on the 1.8m high front boundary walls. The wall is in three sections, with timber slatted fence and gate sections inserted between the three wall sections in order to satisfy Council requirements for 40% visual permeability on the street frontage. The walls are built using solid imperial size concrete bricks from Cape Brick, with a 70% recycled content. By the end of the following day [Friday 23 December], all three sections of the front boundary walls were up and bagged. Bagging entails wiping a cement slurry over the finished surface to smooth it off, while still leaving a discernible brick pattern. This type of finish not only saves time and money, but uses far less cement and sand than plastering, with concomitant environmental benefits. Happiness all round that we got so much done before the start of the Christmas break.

The three sections of street boundary wall

TIME AND TIDE

While we are trying, and so far not very successfully, to come to terms with the devastating loss of Tigger, life goes on inexorably. So our excitement at the rapid progress on site has been somewhat muted, and greatly overshadowed by this departure of a close friend.

Overview of progress thus far

This week, the builders have been on site Monday to Wednesday. Friday was a public holiday, and as things go this time of the year, Thursday was taken off for good measure. Progress during these three days has been rapid. The rear boundary wall has been completed up to its 2m permitted height. A storage shed was delivered to site to keep tools and materials safe, now that building has begun in earnest. And the builders have completed the foundation walls of the house, ready to start compaction of the fill in advance of pouring the ground floor slab.

Completed rear boundary wall, 2m high

View towards the street

In addition, on Thursday we received a delivery of 93sq.m of 40mm thick sheets of polystyrene insulation. The polystyrene was supplied by a company called Isolite, which manufactures the sheets in their factory in Philippi, Cape Town. The sheets measure 2.5m X 1.2m. On Saturday we cut a few of the sheets to size, in order to fill in the gaps left over when the full size sheets are laid in position. This is our first major departure from standard house construction in South Africa, where it is unheard of to insulate one's ground floor slab. This 40mm layer of insulation will be placed over the damp proof membrane, and directly under the concrete slab of the house [we are omitting insulation in the Garage]. It should make the tiled ground floor comfortable to walk on barefoot in the depths of the Cape winter, without resorting to under tile heating. This should lower the electricity demand as a result, and make for a more comfortable internal environment.

Cavity wall construction at end walls [brickwork to be exposed]

Solid wall construction at long walls [to receive rainscreen cladding]

2009.09.15 -2011.12.13

 

Yesterday was just one week short of Tigger's second year with us. I remember the day I picked him at the shelter. I had never had a cat before, and didn't really know what kind of cat I wanted, except that I didn't want a ginger. I was in the Tears kittenry for over an hour playing with the kids, and had made up my mind on an aloof little black and white boy. All that time there were two little ginger babies fast asleep in a hanging basket. I decided to wake them up just to see what they were like. It was Tigger at the bottom, and his little sister asleep on top of him. She was not too pleased that I had disturbed her beauty sleep, but Tigger promptly climbed up onto my lap and fell asleep there. That was how he picked me. His wiry coat and affection melted my resistance, I knew he was the one.

This terrible disease was probably already in the making at that stage, but there was no way of anyone knowing. I am happy to have given you a home for the two years that you were destined to be here. I can still hear the little gurgling noises you used to make when you were being playful. I can still feel your deep resonant purring in the next room. I so wish you would still come and greet me with a nudge and a curly tail whenever I come home. What I would give to be woken by the sight of you sitting on my chest staring into my eyes, gently purring me awake.

Tigger fought his illness bravely. I aspire to attain his dignity and stoicism in dealing with adversity. Never once did he complain or feel sorry for himself. Tigger, if I could have borne your burden for you, I gladly would have. Yesterday, you could fight no more. I am so sorry for any discomfort you experienced. I wish it didn't have to end this way. You fell asleep gently, gazing into my eyes. You are always unforgettable, my Little Lion.

FRANTIC FRIDAY

Friday 9 December 2011 was a busy day on site. We had 10 pallets of bricks and blocks arriving, Ciolli Brothers were due to pour 17cu.m of concrete, and the builders wanted to get started on the rear boundary wall.

So that's how the morning began. Building of the rear boundary wall started using concrete blocks which had been delivered the day before. This wall is built of MA190 blocks, basically hollow concrete blocks dimensioned 390mm long X 190mm high X 190mm wide. For most of the house as well as the front boundary wall we are using solid imperial size bricks, 220mm long X 72mm high X 105mm wide. All our bricks and blocks are concrete, and sourced from Cape Brick, a local manufacturer based less than 20km from the site. Cape Brick has excellent environmental credentials. Their concrete masonry products have an average recycled content of 70%. In fact they claim to use 10% of all concrete building rubble generated in the Cape Town region in the manufacture of their products. And again their close proximity to site keeps the transportation carbon footprint smaller too. So although we are using heaps of concrete, a huge proportion of it is either blast furnace slag or recycled rubble, so no guilty conscience there. And the longevity of the product as well as its excellent thermal mass characteristics will minimise life cycle costs of the building further.

Our engineer specified that our concrete footings be 300mm thick. The 17cu.m of 25MPa foundation concrete came in 3 separate trucks, the first two carrying 6cu.m each. When we saw how much was still left to pour after the first two trucks, we contacted the supplier to increase the final batch from 5 to 6cu.m. The extra concrete was needed as the trenches became ever wider with the sand continuously falling in and being dug out again. This extra concrete order delayed the third truck for a couple of hours, which gave the builder a little time to keep building on the rear boundary wall. A productive day all round.

The north wall foundation concrete in its final resting place

Progress on the rear boundary wall

Overview of the site from the rear

BUILDING STARTS!

Following a weekend site visit by our foundation engineer, we were advised of the steel reinforcing, and concrete strength and dimensions required for the strip foundations. The steel was ordered on Monday and delivered on site Tuesday 6 December 2011. Our builder, Pieter Olyn, made quick work of cutting and tying the steel rebar, and placing it in the foundation trenches.

Steel reinforcing, consisting of 4 rows of 12mm rebar tied at 750mm intervals with 10mm rebar

The first of 3 batches of readymix concrete was delivered on site Wednesday 7 December 2011. This was a 6cu.m batch of 15Mpa concrete for the boundary wall foundations. We are using a local company called Ciolli Brothers. They have a stone quarry and concrete plant just a few kilometers from the site. The cement specified in the mix is 40% slag [ground granulated blastfurnace slag or GGBS - an effective cement substitute], a waste material collected from iron smelters. This is sometimes mixed with cement in varying proportions and sold as Eco-Cement by some companies. As it is a by-product or waste material, it has a significantly reduced carbon footprint compared to regular virgin cement. This fact, together with the close proximity of the quarry and concrete plant to the site, makes the concrete as environmentally sound as is reasonably possible on a tight budget. Our concrete supplier does not even market his concrete as an environmental choice, and it did undercut the quoted price from large multinational suppliers. My advice, do research on your suppliers and educate yourself about the options, as environmentally responsible materials are not always the more expensive option.

Pouring a section for the front boundary wall foundation

OOPS! Partial collapse of the house foundation trench, cause by the heavy truck

 The concrete pour started with 2 cu.m for the front boundary walls, easily accessed from the road. Getting the concrete to the rear boundary wall trench was a little bit more tricky though. The driver had to manoeuvre the truck down the narrower south side of the site, as the sand on the wider north side was too loose to drive on. After a few tries over this still loose sand, he managed to get through, despite a heart stopping moment of soil collapse into the house foundation trench. The remaining 4 cu.m were poured at the rear boundary, and he went on his way within the allotted 45 minutes.

Pouring concrete in the rear boundary wall foundation trench