Adobe T-Brick Shed: Trenching the Foundation

The plan is to put in a rubble trench foundation. A rubble trench is a trench filled with rubble or gravel. Clever eh? The benefits are of the rubble trench are:

  • No concrete required. The trench will be filled up to grade level and the building will be built directly on it.
  • The rubble drains water away from the building.
  • A moisture barrier. Water will wick up through the soil and concrete through capillary action. With a rubble trench they are air gaps that stop the wicked action.
  • The rubble trench distributes the weight of the structure.

Sounds great except for the whole digging the trench part in hard packed caliche soil. Caliche is a soil that has been cemented together by lime (calcium carbonate). Lime will prove useful later in the building process but for digging the foundation, not so much. Fortunately, we just have to get below frost line which in central Texas is like 6 inches. We’re going for a depth of 12″ – 18″. For the job we rented a trencher which is kind of like a chainsaw for the ground.

Our first trencher lasted for about an hour and a half before giving up

The next day we decided to upgrade a bit to a hydraulic trencher which made a huge difference

The problem with the trencher is that makes a trench about 4-6″ wide. We need a width of approximately 18″.

So we had to dig two parallel trenches.
Jean even got in on the trenching action.

Jean is digging a drainage line from the foundation

As a reward for her grueling labor Jean got a milk shake from P.Terry’s