Getting hooked on an ancient gadget

The basic footing preparations were done, so I could shift my focus to the details.

I had a little more excavating to do, in order to match the footings to the layout and elevations. At this point I opted for some additional resilience. The architectural details specified a two foot wide and one foot deep reinforced concrete footing. Some number crunching convinced me that the incremental cost of increasing the footing width from two to 2 ½ feet would be worthwhile. Plus, we had the room to add three inches to each side.

Our salvaged porch lumber came in handy. I used the old two by eights and two by fours to build the formwork for the concrete.

This was the moment where precision was not an option but an absolute necessity. The top of the formwork had to be perfectly level since we still have to pour the foundation wall onto the footing. It is a b***h of a task and a huge time suck to build the wall formwork on an uneven footing. So, starting with a perfectly level footing is the way to go.

But how do you do that? Using a spirit level is risky. Its a handy tool, but not precise enough, certainly not over the distance of 42 feet (the total length of the footing). Modern technology has given us the gift of laser levels. But I didn’t have one.

This is where my apprenticeship in the German landscape industry came in handy. I remembered that before the days of laser levels, we used something called “Schlauchwaage” – which translates into hose or water level. And if this nifty gadget was good enough to for the Egyptians to set and check the elevation of the Pyramid footings, it will be good enough for our porch footing.

There are several variations of water levels. I simply used 50 feet of clear vinyl tubing which I filled with water. There cannot be any air bubbles in the water, or they would distort the hydrostatic pressure and render incorrect readings.

Because the water in the tube seeks a hydrostatic equilibrium, the water level at one end of the tube is equal to the water level at the opposing end.

schlauchwaage-01

This gave me an extremely simple yet precise tool to transcribe the exact same elevation across the entire formwork length. You could even use the water level around corners or across different rooms. There’s no need to have a visual connection between the two tube ends.

But beware of the meniscus, particularly in smaller tubing! The surface tension tends to create a concave or convex water surface, which, if looking at it from the right angle, can lead to 1/8 or ¼ inch inaccuracies in readings.

All right, enough gadget talk. The much less precise yet essential rebar layout required my attention. This got me a lot closer to pouring the concrete, which was scheduled for the next day.

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About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

2 thoughts on “Getting hooked on an ancient gadget

  1. I admit the water level is cool, but I still rank my self-leveling laser level up with my impact driver as one of the most useful tools I’ve got, and it was only about $100. It doesn’t replace a string line or a bubble level, but it makes a lot of jobs easier.

  2. Marcus, thanks for posting this series. It is very useful following the progression of this build, given your experience and professional point of view.

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