The total cost of concrete construction work includes the cost of formwork also. Construction of formwork involves considerable expenditure in terms of cost of material, cost of labour for fabrication, erection and removal of formwork and time element. In case of buildings, the cost of formwork may range between 30 to 40% of the cost of concrete work. In case of special structures like bridges, tall chimneys, dams etc., the cost of formwork may range between 50 to 100% of the cost of concrete work, or even more. Since formwork contributes nothing towards the stability of the finished structures, its cost should be kept barest minimum consistent with safety.
Steps for Economy in Formwork
Following steps should be followed to effect economy in the cost of formwork.
The building should be planned in such a way that there are minimum numbers of variations in the size of rooms, floor area etc., so as to permit re-use of the formwork moulds repeatedly.
The scheme of the formwork should be efficiently planned and suitably designed to determine the most economical but safe sizes of different components including the supports or pros.
The formwork should be constructed in such a way that timber (where used) is cut to the minimum and it can be struck off with ease and re-used with least damage.
The quality of finished concrete surface depends to a great extent upon the quality of formwork used in the work. In case the formwork is made out of rough timber and is not constructed properly, the resultant concrete surface will be irregular and full of defects. The expenditure involved in rectification of defects in such works is invariably more than the saving made in the cost of formwork.
Thus to effect economy, the formwork should be made with good quality material and should be constructed properly following the steps mentioned as above.
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