After completing the perimeter of the slab with the 90° rebar, it was time to work on the mat for the slab.  This is when it gets difficult to walk and takes more time.

Some Rebar Basics and Our Requirements

Reinforcing steel, rebar, strengthens concrete walls to help minimize cracking and buckling under load.  Since we need a ‘concrete boat that is heavy enough to sink and strong enough to avoid breaking and cracking as it sinks’, we need a fairly strong mat slab and foundation walls.

For our project, our structural engineers (Duquette Engineering) specified the requirements for the rebar in the mat slab and the foundation walls.  There is a two-layer grid required for both the horizontal mat slab and vertical walls.  The horizontal plane is connected to the vertical plane with #8 rebar bent at a 90 degree angle.  These pieces are set every 6 inches on center.  The horizontal mat slab has two layers of #5 rebar with each direction spaced 12 inches on center (creating a grid).  The minimum distance rebar can be from the exterior surface is 2 inches. so spacers are used.  One of the tasks when setting the rebar in place is to tie the pieces together with wire.  Very tedious work.

Oh, the diameter of the rebar is the number multiplied by 1/8 of an inch.  Thus, a #5 rebar is 5/8 of an inch in diameter and #8 rebar is a full inch in diameter.

Laying the Rebar

Positioning the materials in advance.

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