What is “back propping” (with regards to formwork) and what are the important issues to be observed?
“Back propping” can refer to shoring up of forms to support overhead concrete. In this case, the forms are supported by temporary steel or timber beams and as many vertical posts as required. Once the concrete has achieved sufficient strength to support itself, the forms can be removed. The form work is actually designed to support the wet concrete weight + construction loads of workmen placing the wet concrete and equipment. The forms should be straight and true to line and should not be deflecting as the concrete is placed on the forms. For vertical concreting projects, such as the placement of concrete walls, the forms into which the concrete is placed are separated by the wall thickness desired. The reinforcing steel is located within the space between the forms. As the concrete is placed in between the forms, the pressure of the concrete tries to push the forms apart from each other, but the forms are tied together with small flexible wires called form ties. As the concrete fills
