Stools are also known as chairs. The purpose of stools is to retain reinforcement at the exact location as well as detach the top reinforcement & bottom reinforcement or to arrange sufficient spaces among the meshes.
The dimension of the stools varies as per needs.
While installing the main mesh reinforcement throughout construction, steel chairs are important to retain the spacing uniformly and retain the mesh reinforcement in place ahead of and after concreting.
The stools have good strength to withstand the loads devoid of modifying the gap of two layers. 12mm or 16mm bars are used to make the stools.
Based on the construction, several types of stools are available like wire chairs, plastic chairs, or small concrete cubes or cylinders. Some are even little dog bone shapes. It is also seen in raft reinforcement in foundation & footing.
The thickness of stools is dependent on the size of footing and slab. The spacing of stools generally remains 1 square meter for one stool. The diameter of stool is equal to diameter of main reinforcement.
The stools are found in the slab specifically in the downward portion of bent up bars to maintain exact spacing between top reinforcement & bottom reinforcement.
The height of the stools = Slab thickness – (2 x Cover + diameter of the top and bottom bars).
Stools are used to separate the top reinforcement mesh and bottom reinforcement mesh. Dimension of the Stools could be change as requirement. Those should be strength enough to bear the loads without changing the gap of two layers. 12 mm or 16 mm bars are used to make the stools.