Rebar chairs are provided to keep the top reinforcement bars of slab, raft, footings etc in place during installation and concreting works.
The chair shall be of sufficient dimensions to provide the good rigidity to top reinforcement bars. also the placing of the chair shall be adequate in number to serve the same purpose.
The chair shall have 2 legs which are resting on the bottom reinforcement mesh of member and each leg should be tied to 2 cross bars of bottom mesh to prevent the toppling of chair during movement.
Height of the chair should be the distance between top and bottom rebar mesh of member.
length of the top portion of chair should be as per diameter of the bar which does not allow bending of chair under human load or material movement load.
Length of the legs shall be adequate to make sure tying on 2 cross bars of the mesh.
in general the length dimensions for smaller sections varies between 100mm to 300mm.