Before starting any construction project, you must ensure that all materials are delivered to the construction site on time. However, this is only possible if you have a detailed list of materials and inputs for the project. This is where quantity takeoff comes into play: estimating quantities based on information provided by construction drawings and other project documents.
Because quantity estimating uses design documents as a starting point, design errors lead to incorrect estimates. You can avoid this by delegating the entire design and construction management process to a qualified engineering firm. This ensures a code-compliant project, quick approval with the local building department, and a construction process free of excessive costs and delays.
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An accurate survey of quantities is also a valuable tool for purchasing managers, as they can know the exact inputs needed during each stage of construction. Materials with long lead times can be ordered in advance, ensuring that the project is not delayed due to lack of inputs. Efficient purchasing of materials has become especially important in 2021 as supply chains have been disrupted around the world.
What is quantity takeoff?
Once you become familiar with construction drawings, you will be able to easily identify MEP components such as air ducts, lighting fixtures , plumbing lines, HVAC units, etc. However, the drawings do not show the exact quantities of material needed to install these systems. During the quantity takeoff process, a construction estimator will determine the quantities of materials and other supplies needed to complete the project.
For example, a construction drawing may indicate the number and distribution of light fixtures in a large room while specifying the branch circuits needed to power them. With this information, the takeoff estimator will determine the electrical materials needed and their quantities. Following are some materials you can find in the list:
- Quantities of conduits and their respective diameters.
- Electrical accessories such as connectors, couplings, elbows and conduit strips.
- Number of wiring rolls, including gauge and insulation colors.
- Quantities and types of circuit breakers.
- Clamps, hooks, and brackets are required for light fixtures.
Knowing the number of luminaires and branch circuits is not enough to purchase the necessary electrical materials. Once the quantity takeoff process is complete and you have a detailed list, you can proceed with shopping. The quantity estimate will not only tell you the quantities of materials needed, but also information such as skilled labor and equipment hours. This means that quantity estimation is also useful for hiring specialized subcontractors or renting equipment.
Accuracy is very important for quantity surveying, especially when it comes to materials that have high prices or long delivery times. If you overestimate expensive materials, the cost of the project can increase dramatically. If you underestimate materials with long lead times and need to purchase more during construction, the project could experience major delays.
Manual takeoff vs software automated takeoff
Quantity taking has traditionally been a manual process, where an experienced estimator analyzes construction documents to determine quantities of materials and other inputs. However, modern design software offers automated takeoff, which is much faster than a manual procedure. However, there is a common misconception that software can replace a human takeoff estimator.
The software will process the data based on the instructions provided by the user, which means wrong instructions will lead to incorrect results. To use quantity takeoff software correctly, the operator must be familiar with the process. Manual takeoff is also useful when you need to double-check software results, especially when dealing with critical building systems.
Generally, Building Information Modeling (BIM) Software is capable of automatic quantity takeoff. Based on the geometric construction model and material properties specified for each component, the software can generate bills of materials. By relying on software, construction estimators can handle more projects simultaneously. Instead of wasting many hours on manual surveys, they can manage and review automated software surveys for multiple projects.
Fast, Accurate Quantity Takeoff: A Competitive Advantage for Contractors
Contractors who optimize their quantity takeoff procedure have a competitive advantage. They can estimate project budgets more accurately and submit bids before competitors. An accurate survey also reduces financial risk, as contractors can know exactly how much they will spend on materials and other supplies before starting the project.
When a project's material requirements and inputs are accurately known, construction managers can ensure everything is delivered on time. Generally, contractors are responsible for any costs they did not consider during the bidding phase and are penalized with heavy fines for missing deadlines. With an accurate quantity taking process, you can avoid both of these problems.
