These updates should probably happen more frequently but in reality, things move so quickly and are so overwhelming that its only now with completing this stage, that I feel I can properly report on it. The focus of these last two months has been to prepare and pour the foundations. Things that we thought would be obvious were stressful to figure out and the whole thing had a very abstract quality because you can’t easily see what you’re doing when you are operating 1m below ground level.
We started by marking the whole site up with pegs and chalk. Starting at one corner, we used the 3:4:5 rule and then checked it was square by measuring across the diagonal in both directions. We used small pegs because the digger-loader had to be able to move about in the space but in retrospect we would have raised tall markers supported on three sides. The main reason being that once the whole building site is filled with mounds of earth, it becomes nearly impossible to measure and check things again. And you need to keep on checking (once the foundations are dug, when the shuttering goes in and in our case, to mark the placement of the steel pads that go into the concrete plinths). If we had to dig again, we would have ensured that the earth was piled to the outsides of the building.
After the digger loader had dug all the major foundations, the site looked like a series of small clay hills. It’s been quite a mess to work on site and made doing things a challenge. Moving forward, we are hoping to remove a lot of this material. Fortunately, a few local farmers have offered that we can off-load some of this on their land.
The property is mostly dense clay and gets a lot of water in the winter and then dries out in the summer. In addition to the building being designed in three separate parts that will settle individually, the engineer also specified a wider and deeper than usual strip foundation. In terrain that won’t experience much settling, it is typical to have a foundation of 600mm wide by 200-250mm deep. Our foundation is 800mm wide and 250-350mm deep. The concrete pump actually poured deeper than intended so in some places the foundation is now closer to 450mm deep. The plinths that will hold the steel columns are at least 800mm x 800mm and stand 200mm above the natural ground level to avoid the steel feet standing in water. It was a lot of concrete. In the end we used 76 tons of concrete! Our building is going nowhere.
To deal with all the water coming down the hill on the property in winter, a wide storm water channel had to be laid behind the house to divert the water away from the foundations. We searched high and low for these blocks and they were proving to be rare and expensive. Then one day I drove past a road works site in Stellenbosch where they were upgrading a pavement and removing these old storm water channels. I asked if I could have them and the foreman gave them to us for free on condition we collected them ourselves. This would have been an unbelievably expensive item which we really needed and would have been yet another unforeseen cost but we got lucky. It turned out to be just the right amount of blocks for the length we had to lay. What a score!
The strip foundations and the plinths had to be poured separately, starting with the strip footings. To do this, we had to put up shuttering on either side of the plinth and then pour in between. Again, we scored by finding some second hand shutter board on Gumtree, which would have cost double had we bought the boards new.
Next, we laid rebar in the strip foundations areas in a lattice grid of 3 long sections, tied together with short pieces every meter or so. These were then raised with half bricks to bring them out of direct contact with the ground and damp, and to have them in the correct position to reinforce the concrete at its weakest point.
And then the momentous day of pouring came (10 March 2022)… what a giant mess! It happened so quickly that we didn’t have time to consider things very carefully and what we now know is that one should prepare an area for left over concrete and that there should be very easy access to all the places where the pouring will happen.
It works out far cheaper to buy ‘readymix’ concrete than to buy the materials yourself and mix on site by hand or with a rented concrete mixer. Even on the day that we needed the pump truck for the first pour, it was still the more cost effective route to go. But it’s a messy process that leaves a lot of spillage and all the concrete in the pumping crane needs to be dumped somewhere on site. Had we known this, we would have prepared part of the driveway to be this remaining pour but now it will simply serve as expensive back fill.
After a few days of curing, the shuttering for the plinths could be put together. To save money, M190 blocks that will be used elsewhere in the house later on, were stacked on each side to make the walls of the plinth blocks. The steel engineer dropped off the base plates and then we were confronted with the head scratching task of how to place these little steel ‘tables’ in the wet concrete blocks absolutely perfectly square and aligned. This is where having the tall marker became essential but fortunately we were able to get these in place so that we could position the base plates accurately. For this stage of the pouring, the ready mix was poured using wheelbarrows straight from the mixing truck.
Finally, after weeks of prepping, stressing and persevering in the heat, the foundations are ready to receive the steel building. The next step will be to have the last measurements taken and then the building can be erected. In the meantime, we can carry on with building the stub walls and making preparations for the slabs. I’ll keep you posted.
For now, watch the video below and if you have any questions, don’t hesitate to contact me on info@ownerbuilderinsouthafrica.co.za.