Concrete formwork, also known as shuttering, is essential in construction, serving as the mold for pouring concrete. Accurate measurement of formwork is critical to ensure fair payment to contractors based on the terms of the contract. Payment can depend on whether the cost of formwork is included in the concrete construction unit rate or is billed separately. This article delves into the process of measuring formwork and the nuances involved.
Understanding Formwork Measurement
Formwork is measured based on the area in contact with the concrete surface. This includes all the vertical and horizontal surfaces where the concrete is poured. It does not include surfaces that rest directly on the earth or areas left open, such as the tops of footings or slabs.
Examples of Formwork Measurement
- Footing Formwork
The formwork required for concrete footings includes the surface area of the four vertical sides. The bottom of the footing, which rests on the earth, and the top, which is open, do not require formwork. - Beam Formwork
For beams, the measurement includes the two vertical sides and the bottom. The top, which usually supports the slab, is excluded.
Challenges in Measuring Formwork
- Reuse of Forms
Although formwork is often reused multiple times, the payment calculation is typically based on the total contact area with concrete. Materials like aluminum and steel offer higher reusability compared to wood, which has a limited lifespan. - Complex Shapes
Concrete structures with intricate shapes increase formwork costs due to higher labor requirements and the inability to reuse custom-shaped forms. - Planning for Efficiency
Construction plans must prioritize maximizing the reuse of forms to reduce costs and ensure efficient resource utilization.
Exclusions in Area Deductions
Certain areas are not deducted from formwork measurements, even though they may not physically contribute to the formwork surface. These include:
- Intersections of beams.
- Beam-to-column or beam-to-wall intersections.
- Openings or cutouts in slabs.
These exclusions ensure simplicity in calculations and fairness in payments.
Units of Formwork Measurement
Formwork is typically measured in square meters (m²) or square feet (ft²), based on the contact area with the concrete. Accurate dimensions should be recorded to the nearest centimeter or inch. It’s important to note that the contact area, not the total formwork material used, is the basis for measurement.
Types of Concrete Work and Formwork Measurements
The formwork requirements vary with the type of concrete structure, each measured separately. Common categories include:
- Foundations and Footings
Includes bases of columns, mass concrete, and precast shelves. - Walls and Vertical Structures
Measurements include walls of all thicknesses, pilasters, buttresses, plinths, and string courses. - Suspended Floors and Roofs
Includes landings, balconies, and their supports. - Beams and Cantilevers
Lintels, girders, and cantilevers are measured for their vertical sides and bottom surfaces. - Columns and Posts
Includes vertical supports like columns, pillars, posts, and struts. - Stairs
Regular stairs exclude landings, while spiral staircases include them in the measurement. - Complex Structures
Includes domes, arches, vaults, shells, folded plates, chimneys, and shafts. - Other Elements
- Waffle or ribbed slabs.
- Edges of slabs, floor breaks, and cornices.
- Fins, louvers, and other decorative structures.
Precise measurement of formwork is crucial for fair payment and effective construction cost management. By understanding the contact area and adhering to established standards, contractors and project managers can ensure accurate billing. Moreover, efficient planning and maximizing formwork reuse can significantly reduce costs, making the project both economical and sustainable.