June 17, 2014

North Roof - Parapet Wall & Drain

Work on the north room roof continued with the of building a parapet wall around the perimeter of the earthen roof. Providing for a drain from the north room roof across to the south where the natural pitch would move the water away from the building.

About 14-ft of 3"-dia ABS pipe was required to establish a drain-path along the wall separating the large main room from the circular dome room.  I had to design the drain inside the wall in order to efficiently move the water from this north roof to the south side of the building to take advantage of the natural grade of the land which slopes to the south.  I had to use a pick to curve-out a channel in the cob of the existing wall.  It's incredible how hard a basic clay/straw mix can be. It took several hours to carve a simple trench to accommodate the pipe.

In the photo below A 90-deg elbow and drain collector was attached to the north end of the pipe in order to act as the collection point for the north roof.

A found an old plastic battery enclosure in my resource area (aka 'the junk pile') to use as framework for a mold for the drain box in the parapet wall. The photo below shows enclosure on top of the drain and the cob wall built-up around the box to act as the outer form of the mold.

The string-line shown in the photo will be the finished height of the parapet wall.  The final height was established using a surveyor's level to ensure height uniformity.  The photo below shows concrete poured in the mold to create the drain box and some concrete to establish a solid collection area for the drain.

The photo below shows the formed concrete drain-box with the plastic battery-box framework removed. At the entrance of the drain collection area, a concrete floor area was added as robustness, for water that will drain into the box from this specific north roof.  

Finally, an overall of the north roof, showing the finished cob parapet wall, earthen roof and drain area at lower-left of photo below. 

I found a section of fired-clay pipe at a salvage yard and it sliped over the 3-inch ABS pipe.  Even though cob (clay/straw mix) would cover the pipe as the walls continue to rise, you can see in the photo I bent into a "U" shape a piece of rebar and pounded it down into the cob wall to secure the clay pipe in place.

The clay pipe shown below extending a couple of feet out from the south side of the building.  The cob wall is now shown built-up above the pipe.

Note: The next steps will be to pour a concrete top-cap and waterproof the earthen roof with a rubber membrane.  Those steps will be posted next as completed.

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