FORMWORK IN CONSTRUCTION

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According to the Concrete Reinforcing Steel Institute (CRSI), “form work and its associated labor is the largest single cost segment of the concrete structural frame—generally more than 50%.”

          • maintaining constant depth of horizontal construction
          • maintaining constant spacing of beams and joists
          • maintaining constant column dimensions from floor to floor
          • maintaining constant story heights

Standard Forms

Since most projects do not have the budget to accommodate custom forms, basing the design on readily available standard form sizes is essential to achieve economical form work. Also, designing for actual dimensions of standard nominal lumber will significantly cut costs. A simplified approach to form work carpentry means less sawing, less piecing together, less waste, and less time. this results in reduced labor and mated costs and fewer opportunities for error by construction workers.

Repetition

Whenever possible, the sizes and shapes of the concrete members should be repeated in the structure. By doing this, the forms can be reused from bay to bay and from floor to floor, resulting in maximum overall saving. The relationship between cost and changes in depth of horizontal construction is a major design consideration. By standardizing the size or, if that is not possible, by varying the width and not the depth of beams, most requirements can be met at a lowered cost, since the forms can be reused for all floors. To accommodate load and span variations, only the amount of reinforcement needs to be adjusted. Also,experience has shown that changing the depth of the concrete joist system from floor to floor because of differences in superimposed loads actually results in higher costs. Selecting different joist depths and beam sizes for each floor may result in minor savings in materials, but specifying the same depth for all floors will achieve major savings in forming costs.

Simplicity

In general, there are countless variables that must be evaluated, and then integrated into the design of
building. Traditionally, economy has meant a time-consuming search for ways to cut back on quantity of materials. As noted previously, this approach often creates additional costs-quite the opposite effect of that intended. An important principle in form work design is simplicity. In light of this principle, the following questions should be considered in the preliminary design stage of any project

   1) Will custom forms be cost-effective? Usually, when standard forms are used, both labour and material costs decrease. However, custom forms can be as cost-effective as standard forms if they are required in a quantity that allows mass production. Class A1 concrete finish

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