With 3D technology, earthwork modelers and surveyors can view virtual models of proposed projects before the groundbreaking work commences. Different types of software can generate such visualizations, and this has led to the BIM vs. CAD modeling debate. Both options have their benefits and supporters.
For anyone new to these software tools, it’s important to be able to make an informed BIM and CAD comparison. Therefore, it is crucial to understand the pros and cons of BIM and, likewise, the pros and cons of CAD.
What Is BIM?
Building information modeling (BIM) is a set of software tools that make it possible to visualize a design idea with realistic dimensions from a multitude of angles. With BIM, design teams and work crews can have a virtual experience of a building, road, bridge or monument before the structure is physically constructed. For all the parties involved in the conceptualization and construction of a structure — including earthworks and surveying crews — BIM provides the following benefits and features:
1. Conflict Prevention
BIM tools allow earthwork teams to determine whether any clashes might occur between a proposed design and the underlying conditions of the site in question. For example, if a building would need deep plumbing yet the ground being excavated sits over thick roots and rocks, these discoveries can be factored into the design plans to avoid issues down the line.
2. Error Reduction
BIM technology makes it possible to catch any errors that initially appeared in a proposed design before the construction work goes into effect. For example, if earthwork crews discover that the dimensions of a proposed building design will not be feasible at the prospective site, planning crews can take this information into account and either make adjustments or change the overall plan.
3. Use in Construction
BIM software is used by construction crews who break grounds on new lands to establish the foundations of roads, highways, buildings, bridges, monuments and structures. The software makes it possible to determine which structures will ultimately work over certain types of soil, thus making the processes involved with earthworks easier for planners and crews.
4. Use in Ground Logistics
BIM software contains a range of features that specifically outline the logistics of plumbing at a given work site. This way, planners can determine whether the stretch of land in question will be suited for the project at hand, be it a tall office building or a wide industrial facility.
5. Use in Planning Piping
BIM solutions make it possible for earthworks crews to determine which type of piping will suit the stretch of land in question. The software can be used to create 3D piping designs that take into account the diameters and lengths necessary to transfer water underneath a proposed building site to the nearest reservoir.
6. Collaboration Tools
BIM solutions offer collaborative tools that make it possible for earthworks teams to interact with other teams in the construction process, from designers and architects to builders, planners and investors. Collaboration tools include communication technology that works across different platforms, allowing cloud-based branches to interact with more traditional departments.
7. Visualization Technology
BIM tools make it possible to visualize a site in 3D and determine how a potential structure will appear from the ground up at a given site. Based on the position of the proposed structure, the tools allow earthworks and construction crews to determine how sunlight will hit the walls of the building or factory and potentially light its interiors.
8. Step Sequencing
BIM software programs arrange the building process in a series of steps from the ground up, including the logistics involved for earthworks crews. The tools can be used to determine how wide the clearance will need to measure for a proposed structure and how deep the ground will need to be broken to support the height and plumbing needs of the building in question.
9. Advanced Features
BIM solutions go beyond 3D technology to make a full-scale planning sequence for earthworks and developers. In new and upcoming versions of the software, BIM is activating tools in 4D, 5D and 6D, giving users the ability to visualize cost logistics in tandem with design concerns. These more advanced features also make it possible for users to determine the thermal and acoustic properties of a proposed building on the site in question.
Potential Issues With BIM Software
On the downside, BIM has yet to be developed to the point of universal compatibility across all branches of the construction industry. Companies and crews that have fully embraced the technology may have problems communicating certain ideas, information and visuals with cooperating entities that still rely on older technology.
Due to the relative novel nature of BIM technology, expertise in BIM software is a relatively small field. Consequently, there are few technicians to consult when users need outside support on a given issue.
What Is CAD?
Computer-aided design (CAD) is a set of software tools that allow designers to create 2D and 3D virtual models of buildings, structures, machines and parts. For surveyors and earthworks crews, CAD makes it possible to review a proposed structure before commencing work on the ground. The features and benefits of CAD can be summarized as follows:
1. Enhanced Visualization
CAD software makes it possible for designers and project developers to visualize a product or part in advance of its production. The software can be used to examine a proposed design from a variety of angles, both inside and out. Whereas conventional designs offer a flat illustration of a proposed idea, CAD makes it possible to step inside of a design and view it from a 360-degree perspective.
2. Improved Communication
CAD allows developers to communicate about the logistics and dimensions of a given design and make improvements as discoveries come to light. For earthworks crews in need of new tools and machines for an upcoming set of tasks, CAD provides an easy way for designers to communicate with team supervisors.
3. Use for Structural Engineering
CAD software accommodates the various aspects of structural engineering. Moreover, most CAD programs offer functionalities that apply to specific industries and the various branches that the projects entail. For projects that involve railroad, tunnel or freeway construction, the design features take all the dimensions into account as the design team drafts a 3D visual of the proposed structure, which earthworks teams can then examine and use to visualize the intended finished project.
4. Use in Earthworks Logistics
When the design for a proposed building, road or bridge is created on a CAD platform, the visualizations that the technology provides makes it easier for earthworks crews to foresee how the finished structure will look from the ground up. This knowledge can then be compared to the findings of work teams as they survey the land in question and prepare to break ground.
5. Accurate Design Specs
CAD platforms make it possible for civil engineers to generate maps and analyze specs across a stretch of land. This research enables better-informed designs for railways and tunnels, thus reducing potential errors and costly redrafts down the line. This information can then be communicated to earthworks crews, making the overall plan more efficient and easier to bring to fruition.
6. Input and Feedback
CAD platforms allow conceptualists to take a raw idea and turn it into a three-dimensional design. This allows different branches of a development team to mutually review a proposed design idea and make suggestions that can easily be implemented. If an earthworks supervisor spots an issue with a proposed design, the designing engineer can immediately take this feedback into account.
7. Advanced Tools
CAD software comes equipped with various design tools that facilitate ease of use and also make it possible to achieve visualization effects that would not be possible with a flat illustration. For example, both 2D and 3D CAD software contains a gripping feature that allows designers to pull, alter, adjust and reshape the dimensions of a proposed structural concept. If an earthworks supervisor reports that a road or pavement design requires an adjustment in width, a grip tool can help employees quickly make those changes.
Potential Issues With CAD Software
CAD software typical takes time to master, meaning that the cost of training can be high and the learning curve can be long. Moreover, the number of CAD experts is relatively small, which can make it difficult to find help if a problem arises.
For any company that has yet to migrate to a cloud server, CAD would be a step removed from that company’s technical infrastructure. As with most new technology, CAD is primarily designed for companies that are up to date on today’s more advanced systems.
What Are the Differences?
A quick rundown of the features of BIM and CAD makes the two seem rather similar. So how do you compare BIM and CAD? The two have some crucial differences that make each more suitable for different types of projects. So what is the difference between BIM and CAD?
CAD was developed to design virtual models for everything from appliances and furnishings to automobiles and rolling stock. CAD software tools are used to create 3D visualizations of the surrounding bodies of vehicles and tools, as well as the smaller parts that comprise the motors and fans inside each machine.
CAD can be thought of as a computerized sketchbook in which designs are hashed out and ultimately refined in 2D and 3D renderings. Each line works independently of one another and can be adjusted or eliminated without affecting any of the surrounding or underlying lines in the design. Therefore, if the design for a parking lot or road requires an extra three feet on one side, you can adjust the line that represents that side accommodate the change in dimensions.
Complex CAD designs consist of numerous sheets, each with separate lines that are overlaid in a virtual file. If a design needs to be adjusted, you must adjust all the layers affected by this change individually. If a design consists of many layers that must each be adjusted in tandem with the others, making revisions can be complicated. With CAD, there is no way to synchronize the layers into a single-action item for a multi-layer adjustment.
BIM was developed more exclusively for the virtual design and multi-dimensional visualization of proposed building ideas. As such, the tools are designed to digitally render the complex dimensions of all the parts that comprise the interior and exterior of a residence, factory or office building, including the walls, stairs, doors, windows, ceilings, plumbing, wiring, lighting and ventilation.
A major difference between BIM and CAD is the interactivity of the different dimensions during the editing process. In BIM, the dimensions that comprise an object are interconnected. Therefore, any adjustment that needs to be made in a building design, such as the width of a wall or corridor, can be done in a single edit.
In BIM, the dimensions of a given detail can be synchronized to all instances of the detail in question. For example, if the windows on a building are initially designed to be 3.5’x5’ and need to be adjusted to 4’x5’, you can change all the windows on the virtual building with a single adjustment.
What Is Right for Me?
Earthwork modeling and surveying teams can use BIM software to determine the ground dimensions of a proposed structure. Surveying crews can take a proposed building design and determine whether the chosen piece of land is right for the project in question. Earthworks modelers can then use the software to design the depths and dimensions at which ground will need to be excavated to set the foundations and build the sub-levels or layers of the building, factory, road, parking lot or structure.
For earthwork modeling, BIM tools can facilitate a more efficient flow of tasks because the software is designed to edit complex dimensions in a few steps. When all the dimensions of a construction layout are taken into account, BIM offers a more complex set of dimensions from various angles in a virtual preview. This way, all the parties involved in the construction can review the measurements beforehand and make suggestions or edits in advance of the project’s starting date.
BIM software tools can be especially advantageous for earthwork modeling of designs that consist of multiple levels. For example, if a development team proposes a multi-level courtyard across an acre of land, BIM tools can be used to accurately render the dimensions of this idea. The surveying team can then review this virtual design and provide suggestions and feedback. Construction crews can then reference this final design when it comes time to break the ground for the courtyard.
Data Preparation by Take-Off Professionals
For complex site work, it’s crucial to have 3D models to preview before construction begins. Take-Off Professionals is staffed by a team of expert engineers who develop 3D models for earthworks projects. Regardless of the size and complexity of the project in question, we can prepare data the way you need it. Contact Take-off Professionals to learn more about our 3D modeling services.
As a professional involved in architecture, engineering and construction (AEC), you’re likely familiar with quantity takeoffs. The term has been around a long time in the building industry, and it reflects an important part of the planning process. Quantity takeoff requires a highly specialized skill set to do data management correctly.
This crucial step in a project’s early stage can make or break success. In fact, improper quantity takeoffs can underestimate or overestimate construction costs, causing inefficiency in the entire construction chain.
It can be detrimental to any job when required material amounts and realistic pricing values are overlooked or duplicated. The key to successful construction data collection is thoroughness and accuracy.
What Is a Quantity Takeoff?
Explaining what a quantity takeoff is in construction is relatively straightforward. Essentially, a quantity takeoff refers to estimating materials. You review the project plans and take off information about what physical materials the architect, engineer or draftsperson specifies to assemble the project.
Quantity takeoffs have many other names, including:
- Estimating takeoffs
- Construction takeoffs
- Earthwork takeoffs
- Material takeoffs
- Material estimating
- Material counts
- Quantity surveying
Regardless of what you call them, quantity takeoffs are material-specific. As a rule-of-thumb, quantity surveyors or takeoff specialists don’t account for other project needs like labor, overheads, permits, insurance, equipment or incidentals. They stick to isolating material requirements and transposing that information into cost-based estimates.
Technology has changed the quantity takeoff method, and for larger construction companies, computerization has been invaluable.
Today, advanced processes like Building Information Modeling (BIM) raised the technological bar with more complicated systems than used in the past. However, computers significantly increase estimation accuracy. This helps to solve the age-old problem of low productivity and excessive waste elegantly outlined in a commissioned report by the Economist Intelligence Unit.
Computer-aided design (CAD) programs revolutionized the building industry. Many modern projects are built twice. They start life as virtual environment models that work out the bugs and then move forward with reduced-risk structures in the real environment.
While computerization has increased takeoff accuracy and speed, the human element in quality takeoff examples can’t be replaced. Digital takeoffs are still at the mercy of human operators and interpreters just as manual takeoffs are. Today, we still rely on two quantity takeoff methods — manual and digital.
1. Manual Material Takeoffs
This is the oldest and simplest material takeoff form. Manual material takeoffs involve the estimator taking physical plans or blueprints and carefully detailing every material type and quantity specified on the construction drawings. This is a time-consuming data management process and prone to human error. It’s the estimator’s knowledge of materials, experience in estimating and skill in taking off material quantities that ensures accuracy. With manual methods, there’s no substitute for attention to detail.
2. Digital Material Takeoffs
Performing material takeoffs through computer analysis and database application is relatively new in the construction industry. The first effective CAD-based programs date back to the late ’80s and ’90s, and their sophistication quickly evolved to include computerized building models integrated with digital takeoffs. Digital takeoffs are superior to manual methods for large and complex projects because of their speed and thoroughness. The qualifier is the takeoff technician being properly trained and proficient with the software application as well as highly attentive to applying the takeoff information into cost-based results.
Quantity takeoffs can be complex and involved processes. However, they have a single purpose, and that’s accurate data management. Whether you employ manual takeoff personnel or equip them with the latest digital takeoff program, the outcome must be an accurate list of all materials required to complete the project. It also has to conclude with a meaningful price structure.
Who Needs to Do Quantity Takeoffs?
Everyone involved in organizing the front end of a building project needs to do quantity takeoffs. Material takeoffs aren’t a tail-end qualifier. They’re a critical step that begins the bidding process to propose a realistic contract based on accurate material and financial information.
No matter how small or large your project scales, you have to start by calculating how much it will cost and how much material it will need. That’s whether you’re looking at a single residential unit or a larger subdivision undertaking with compounded earthworks, utilities, road surfaces and integrated above-ground structures. It begins by taking off materials, understanding what you have to work with and predicting the eventual price.
Architects, engineers and construction managers aren’t the only people needing to do quantity takeoffs. No matter what industry you’re in, if you build anything at all, you’ll require material calculation and price estimates. Here’s a list of professionals who need to do material takeoffs:
- Urban master planning and smart city designers
- Tunneling and subway architects
- Residential home builders and renovators
- Rail and metro transportation engineers
- Offshore and marine architects
- Landscapers and landscape architects
- Highway and road engineers
- General contractors and construction managers
- Energy and utility contractors
- Civil, mechanical and structural engineers
- Architects and all building designers
Conducting a quantity takeoff takes skill, patience and powers of observation. It also takes a lot of experience. Quantity surveying is a high skill and a vital component to support project proposals. In fact, material data estimation is such a critical part of construction that many managers retain specialized independent takeoff professionals to do quantity takeoffs for them.
How to Do a Quantity Takeoff
Like every facet of infrastructure in building construction, quantity takeoffs are a process. Learning how to do a material takeoff is a skill people can potentially manage if they have the time and resources to train in their system and then allow field time to polish their skills.
Learning in the field can be expensive. Humans are prone to error and manual takeoffs are especially open to misinterpretation, omission and wrongful calculation. So are digital takeoffs if the source input is wrong or the program operator fails to apply sound principles.
There are two ends to ensuring quantity takeoffs are sound and therefore meaningful. Deviating from either path can result in mistakes that can compound errors. An input error is sure to create a wrong end-calculation, and a bad output mistake can have equally damaging effects on money, time and inefficiency.
Getting a quantity takeoff correct is a matter of following a proven process. This formula has been around for years, and it’s the same method whether you use manual or digital takeoff methods. These are the two parts of doing an accurate quantity takeoff:
Proper material takeoffs begin with inputting accurate information into the plans. Whether your draftsperson still hand-draws blueprints or your CAD operator creates multi-layered, three-dimension building models, your takeoff technician is paramount to managing data. This starts by inputting precise information onto the blueprints or into the computer-assisted takeoff software.
Your takeoff personnel only have so much control over what they’re given. Normally, a designated estimator won’t prepare the original concepts, working drawings or CAD layouts. Others in the building chain usually design and specify projects. However, an astute takeoff tech can spot irregularities and account for them during their data management. This is a critical control in the input stage.
Performing material takeoffs is core to the data management output stage. Output turns concepts into physical entities, and this is where accurate material estimation is essential. Putting out hard figures from software printouts creates solid estimates, which are the foundation for successful bids.
Here is where your takeoff person or team has control. Setting aside errors and omissions, your material takeoff relies on a system of identifying materials, quantifying them and then attaching data to a price schedule. This systematic approach, if done right, results in a fair an accurate proposal to move the project forward.
Construction data management professionals take material takeoff output and put this information into schedules based on valid pricing structures. In small-scale projects, estimators might use values based on local suppliers or subcontractors. In large building proposals, estimators often use national pricing. Takeoff professionals know where to look for quality data to use in a quantity takeoff.
What to Look for in a Quantity Takeoff
For the most part, doing a quantity takeoff is a mathematical exercise. You extract or extrapolate material figures on the input side. On the output end, you reference your material figures to values. This creates a base for a total project estimate which adds in additional costs for labor, equipment and overhead.
You’ll hear the term “quantify” used in material takeoff discussion. This is the name for identifying quantities of material being estimated. It might be the quantity of cut and fill required for earthworks. Or, it might be the quantity of pipe, steel or lumber necessary to complete a structure.
Quantity surveyors or material takeoff professionals have a special challenge. They have to turn two-dimensional plans into three-dimensional images to quantify them. Accurate quantity takeoffs come from both the two-dimensional and three-dimensional worlds.
With manual takeoff methods, the surveyor needs to think two and three-dimensionally and visualize the concept. Digital takeoff methods relieve a lot of this spatial load, but a technician still has to manage that data. Here are the base formulas takeoff professionals use to look for and quantify construction materials:
- Unit count: This is the simplest takeoff task, yet it’s easy to miss something in a unit count. When planning a building, estimators will count single items such as light fixtures, pipe fittings or door knobs. They calculate the total unit figures and multiply by unit price to achieve a gross total.
- Linear length: Total lengths or runs are specific to materials like lumber, steel and piping. These building products are difficult, or nearly impossible, to unitize. Estimators will add up the combined linear lengths of materials in this category and also add a gross value to it.
- Surface area: Accurately estimating surface area materials is still a two-dimensional task. It doesn’t matter if it’s flatwork stones, floor coverings or roofing materials. The calculation is length times width, and this total gets quantified to a value.
- Cubic volume: Here’s where the three-dimensional reality enters the material takeoff business. Earthworks, concrete pours and insulation are prime examples where you’d use a cubic volume takeoff. This is length times width times height, and it’s applied as a unitized number on a value column.
- Physical weight: Calculating construction by weight often happens in addition to other takeoff quantification. You might hear pounds of steel or tons of backfill. Calculating physical weight is necessary when accounting for transportation costs.
Although material takeoff professionals pay strict attention to their two and three-dimensional calculations, they realize their figures eventually support two more construction dimensions. Time is an additional dimension on construction projects, as is cost. Because of time and cost, it’s vital to make sure material takeoffs are done right.
Why Ensure Quantity Takeoffs Are Done Right?
The United States construction industry generates huge costs and consumes massive time. American construction projects generate billions of dollars and employ millions of workers. Because of the money and people affected, it’s important to get material takeoffs right.
You have two main material takeoff options. The first is using the old and antiquated manual method. The other is using a modern and more accurate digital takeoff system. Your choice might depend upon how much time you have and what the cost of a digital takeoff system will run you.
Comparing time and cost against accuracy might be a tough data management decision. Fortunately, you have a third choice. This one makes a lot of sense when you’re under a time constraint and demand estimation accuracy.
It’s turning to a material takeoff professional to estimate for you. These experienced construction experts make sure your takeoffs are accurate, thorough and dependable. You can trust them to support your bids and your business.
Contact the Take-Off Professionals for Help
We’re Take-Off Professionals (TOPS). We’re a team of experienced and knowledgeable engineers who will produce accurate data so you can manage your business and build your projects without construction estimation worry.
TOPS offers takeoff services to meet your individual needs. You might be a small-volume builder needing a simple material list to complement your proposal. Or, you might require a comprehensive plan for cutting, hauling and filling earthworks. Whatever your need, TOPs can help improve your productivity by ensuring you have the sharpest information based on the best material takeoffs possible.
Professional material takeoffs increase your bidding accuracy and work efficiency. This results in saved money and greater profits. For more information on how we can help, call the Take-Off Professionals today at 623-776-9546 or connect with us online.