Measurement of Concrete Formworks for Payment Calculation

Measurement of Concrete Formwork for Payment :

Accurately measuring concrete formwork (shuttering) is essential for the contractor to receive payment for the concrete work completed. Whether the cost for formwork is integrated with the concrete construction per unit quantity or paid separately, as specified in the conditions of contract, will determine the payment due to the contractor.

Factors Affecting Payment for Concrete Formwork:

The payment for concrete formwork is based on various factors, such as the cost of the formwork included in the concrete construction per unit quantity or whether it is paid separately as stipulated in the agreement between the contractor and the client. Accurate measurement of the formwork is, therefore, a key factor in determining the payment due to the contractor.

Measuring Formworks for Concrete Footings

When measuring formworks for concrete footings, the area that is in contact with the concrete surface should be taken into account. For example, the formwork for a concrete footing would only include the four sides of the foundation, as the bottom would be resting on the earth, and the top would be open. To calculate the formwork area, simply multiply 2 x (2 + 3) x 0.6, which gives a total of 6 m².

Measuring Formworks for Reinforced Concrete Beams

When measuring formworks for reinforced concrete beams, the combined surface area of two sides and bottom of the beam should be taken into account. This can be calculated by multiplying the length and width of both sides of the beam, as well as the bottom of the beam, and then adding them together.

Issues in Formwork Measurements

Reuse of Forms: The forms are used more than once in concrete construction but the payment is calculated based on the total contact area of the formwork with concrete and reuse of the forms is not taken into account. Thus, the price per unit area of formwork can be reduced for reuse of the forms. Aluminium and steel forms can be reused for many number of times than wooden forms.

Costlier Formwork Installation for Complicated Shapes: Complicated shape of concrete makes the formwork installation costlier than the simple formwork installation because of labor cost and inability to reuse these forms. A construction plan is required to reuse the forms maximum number of times to make the construction cost effective.

Deductions of Formwork Area: Deduction of formwork area should not be taken for intersection of beams, intersection of beams and columns and walls, and any openings or cutouts in slabs.

Units of Formwork Measurement

Unit of Formwork Measurement: Formworks are usually measured in terms of area, such as square meter, square foot, or square centimetre. Generally, the contact area with concrete is taken as the unit of measurement, since this is the area that is in contact with the concrete. The dimensions of a formwork should be measured precisely to the centimetre or inches.

Calculating Formwork Contact Area

When calculating the contact area of formwork, the formula 2h(L+B) should be used. This formula takes into account the length and breadth of the formwork, as well as the height of the formwork. This will give an accurate measure of the contact area between the formwork and the concrete.

The measurements of formwork are carried out separately for each type of concrete works such as following:

1. Foundations, Footings, and Bases of Columns: Measurements for formwork for foundations, footings, and bases of columns are carried out separately for mass concrete and precast shelves.
2. Walls and Attached Pilasters: Measuring for formwork for walls of any thickness, including attached pilasters, buttresses, plinths, and string courses is conducted separately.
3. Suspended Floors, Shelves, and their Supports: Measurements for formwork for suspended floors, roofs, landings, shelves, and their supports, as well as balconies, are conducted separately.
4. Lintels, Beams, Girders, and Cantilevers: Measurements for formwork for lintels, beams, girders, and cantilevers are conducted separately.
5. Columns, Pillars, Posts, and Struts: Measurements for formwork for columns, pillars, posts, and struts are conducted separately.
6. Stairs and Spiral Staircases: Measurements for formwork for stairs (excluding landings) and spiral staircases (including landings) are conducted separately.
7. Arches, Domes, Vaults, Shell Roofs, and Folded Plates: Measurements for formwork for arches, domes, vaults, shell roofs, and folded plates are conducted separately.
8. Chimneys, Shafts, and Well Steining: Measurements for formwork for chimneys, shafts, and well steining are conducted separately.
9. Vertical and Horizontal Fins: Measurements for formwork for vertical and horizontal fins, individually or forming boxes, louvers, and bands, are conducted separately.
10. Waffle or Ribbed Slabs: Measurements for formwork for waffle or ribbed slabs are conducted separately.
11. Edges of Slabs and Breaks in Floors and Walls: Measurements for formwork for edges of slabs and breaks in floors and walls are conducted separately.
12. Cornices and Mouldings: Measurements for formwork for cornices and mouldings are conducted separately.