Foundation Specifications 0053

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All reinforcing steel must be securely blocked and tied to prevent vertical and/or lateral

displacement during concrete placement. Reinforcing steel should not be hung or sus-

pended from the formwork or templates (the rebar weight can cause settlement in the form

panels affecting pour grades). Top reinforcing steel mats supported by chairs should be

blocked to the forms or sides of the excavation. The bottom reinforcing steel mat which

supports the vertical column steel should be blocked to prevent any settlement. It is required

that all reinforcing steel dowels be tied in place prior to concrete placement and not “stuck

in” during or after concrete placement.

The effective depth of reinforcing steel is critical and must always be checked. For a footing

supporting a single column, pier or wall, the effective depth is the distance from the

centroid of the reinforcing steel to the top of the concrete footing. The bottom mat should

be located at the design depth, even for over-excavated footings, since the vertical column

reinforcement is supported by the bottom mat and the location of the top mat is tied to the

bottom mat by the shear hooks. Lowering the bottom mat is not desirable as it would

require longer vertical steel, longer shear hooks, and may require welded splices on the

longitudinal bars. It should be noted that the additional concrete placed below the bottom

steel mat in over-excavated footings does not increase the design depth of the footing.

Immediately prior to placing concrete, all material which has sloughed into the excavation

must be removed. Check again the clearance between the bottom of the excavation and the

bottom reinforcing steel mat. The foundation material should be wet down but not satu-

rated. To avoid segregation of the concrete, the ends of the concrete pour chutes should be

equipped with a hopper and length of tremie tube to prevent free fall of concrete in excess of

Foundation Problems and Solutions

It is mandatory that the Engineer inspect the excavated surface at the planned footing

elevation after the excavation is completed (Section 19-3.05 of the Standard Specifications

requires the Contractor to notify the Engineer after the excavation is completed). Only by

visual inspection can the Engineer determine if the foundation material is suitable,

disturbed and/or contaminated, or unsuitable.