Size, shape, and alignment of slabs, beams, columns and other concrete structural elements depend on accurate construction of the formwork. Forms must be built to the correct dimensions. Formwork must be rigid enough under construction loads to maintain the designed shape and alignment of the concrete element. If the forms deflect excessively, bulges in the concrete surface may require expensive chipping and grinding. If the forms move out of place, the misalignment can destroy the integrity of the structure or affect installation of the structural frame, the building’s façade, or building equipment. The formwork must stay in place until the concrete is strong enough to carry its own weight and any external loads.
The quality of the surface finish of the concrete is directly affected by the forms and form material. Poor workmanship and a lack of attention to detail while installing formwork will lead to form concrete leakage and rough finishes. If the forms do not produce the specified finish, considerable corrective work such as grinding, patching, rubbing, or coating may be required.
If the job has unusual requirements or special architectural finishes for walls and columns or entails new techniques, it is a good idea to have the crews who will be doing the work construct sample walls or units. Mock- up panels and walls can be built to perfect concrete mixes, fine-tune construction techniques, demonstrate early-age strength, or provide an example of the surface finishes that should be expected. These panels can also help clarify the type of finish desired by the architect. Another place to try sample finishes, sandblasting or coatings is on a wall that will later be backfilled or on an interior wall that will later be covered.