5 November 2020
Using BIM Models and Drawings for Homebuilding Design
‘Get it done on time and within budget!’ seems to be the mantra for general contractors in the AEC industry. Also known as main contractors in the UK, general contractors make it their number one priority to complete projects efficiently, on time and in the most cost-effective manner possible. Typically, general contractors act as project managers. Some of their most crucial responsibilities include studying project-specific documents prepared by architectural firms, applying for site permits and regional licenses, day-to-day site surveying, project cost estimation, time and schedule monitoring and liaising with multiple disciplines, consisting of mechanical, electrical and plumbing services specialists. Fulfilling most of these requirements, BIM (Building Information Modelling) technology has become a firmly entrenched guest at the homebuilding table, and residential BIM modelling services are much in demand.
Since general contractors are responsible and bear the risk for the timely completion of projects, they appreciate greater predictability and a smooth workflow with minimum delays, leading to an effective and profitable construction process. Needless to say, adding a fourth dimension of time scheduling to 3D BIM models can help contractors and discipline-specific subcontractors in the project.
While the 3D BIM modelling concept has been widely accepted by general contractors worldwide, few have actually realised the benefits of adding 4D scheduling to BIM models. Sometimes referred to as simulation-based modelling, 4D BIM plays an integral part in construction planning while helping contractors and other stakeholders evaluate the impact of design features on the construction schedule and workflow.
What is 4D BIM?
Well, since the fourth dimension is time, 4D BIM refers to the 3D visualisation model of a homebuilding project which includes scheduling and sequencing. Project scheduling data is included in the 4D BIM design process, enabling stakeholders to analyse processes and effects sequentially, using visualisation and data.
In 4D modelling, a BIM software application, such as Autodesk Revit, is bidirectionally linked to a project management application, such as Microsoft Project, to monitor the progress of the project. Alternatively, 3D BIM models created using Autodesk Revit are combined with the Autodesk Navisworks TimeLiner tool to create 4D simulations of planned construction processes and sequences.
For general contractors, 4D models can help create a virtual mock-up of the entire construction system design, identify workflow-based clashes and manage the supply chain for materials and labour personnel needed on site.
Virtual mock-ups, also known as sequence-based simulations, can help contractors communicate extremely complex processes to the entire team while improving productivity on site. As a result, projects are implemented on time. Additionally, main contractors can identify time and workflow-based clashes from 4D models, which makes planning for materials, equipment and multidisciplinary personnel in a constrained space and time highly convenient.
Some of the other benefits of 4D BIM are:
Viewing scheduling data in graphical design helps to compare the scheduled plan with the actual plan.
On-site workers are well informed on their proposed tasks at a particular phase of the project and rework is minimised, leading to improved coordination among various disciplines. Contractors can easily coordinate the activities of other disciplines and plan ahead to maximise worker efficiency on site.
Visual data in graphs and datasheets helps planning and moving resources around according to planned schedules of tasks, leading to increased operational efficiency in meeting deadlines.
Using 4D BIM results in generating considerable detailed data regarding building products schedules and the visualisation of a step-by-step process. Lead-time, construction and installation time, allowances for drying and mixing time and the time duration for dependency on other products are examples of time-based data that 4D BIM facilitates for a variety of building components.
In a scenario that uses 4D BIM, can 5D BIM be far behind?
The fifth dimension in BIM incorporates costs. So once 4D BIM (time scheduling) is worked out, the next step is 5D BIM, which includes the accurate generation of quantity and cost estimates, development of rates and the overall costs, excluding any natural calamities or other unforeseen circumstances.
Using 5D BIM can offer the following advantages:
Detailed Cost Estimation
The cost for an entire residence can be calculated in the design process. A high level of detailing using manufacturer details in 3D models and knowing current component rates can help generate a detailed account of the total quantity of each building component required, which can lead to an understanding of the total costs involved.
Easy Option Selection
Architects can select design options easily as per client requirements, since accurate and fast estimations (typically in seconds) are generated while analysing different options. This is useful during the bidding phase for owners, contractors and sub-contractors.
Automated Quantity Take-offs
Any modification on a component impacts its cost, related construction documentation and scheduling. All these changes are calculated automatically. Take-offs and measurements are generated from the model, ensuring data that is consistent with design.
Faster Quantity Take-offs
Automating quantity take-off for cost estimating reduces human error, saves cost and saves time. By linking cost information to the 3D model and scheduling, financial estimations are created instantly, reducing or eliminating the lengthy process of quantifying resources and estimating cost.
Using cloud technology, such as in BIM 360 Design, for the BIM process allows contractors and project managers to access data from anywhere in the world and on any device. Physical presence on the site is not required, helping coordination with different teams on schedules or design changes.
As helpful as 5D BIM has become, 6D BIM takes us even further. The next level of BIM modelling involves additional data for operations and facility maintenance, an addition of the building’s whole-life costs. Some of the information provided can include details of component manufacturers, installation and maintenance details, decommissioning data and energy performance.
One thing’s for sure – 3D and 4D BIM are setting the homebuilding industry on a juggernaut of change, picking up 5D, 6D and other advances on its sure and steady path. Data-laden 3D BIM models with additional 4D benefits, integrated with cloud technology, enables stakeholders in multiple locations to effect alterations, cut costs and calculate quantity take-offs easily and accurately.
Though 4D BIM modelling necessitates certain adjustments to the models so that they align closely to actual conditions, the final output in residential BIM modelling is more than worth this effort. Furthermore, contractors can test various ‘what if’ scenarios and make improvements if needed. Summarising, the simulation of various construction sequences vis-à-vis their planned timeframes enables general contractors to make quick, effective and informed decisions. This decision-making advantage and greater predictability offered by availing of BIM 4D modelling services from reliable and experienced offshore partners results in on-time and cost-effective project completion.