BIM and Shop drawings: An experiential perspective
A relatively less talked about benefit of BIM modelling is in the area of shop drawings. 2D shop drawings are quintessential for contractors (civil, electrical, mechanical, plumbing, etc) who review them for constructability in mind, conduct value engineering and optimization and then generate shop (fabrication) drawings. The shop drawings are typically made for execution of services illustrating details like size of pipe, slope, type of joints, bending angle, length of uninterrupted pipe based on availability in the market, information about hangers and distance, among others.
This blueprint shows a clear picture of the entire construction process, specifies measurements, production standards, and fabrication specifications for prefabricated components, details of construction supplies and other necessities. Ranging from steel beams, trusses, and concrete slabs to elevators, appliances, cabinets, ducting, and electrical layout, shop drawings show a wide range of modular components.
Let’s look at the role of BIM in assisting the process of generating accurate shop drawings. BIM helps identify potential clashes at the design stage and minimizes constructability issues on site.
This process of coordinating and integrating all the services and civil components in a 3D environment before generating the shop drawings strengthens the process of drawing generation and minimizes possibilities of co-ordination issues or human errors as compared to hand drawings.
Typically, MEP (mechanical, engineering, plumbing) contractors face challenges like – inaccurate component installation due to insufficient details in the drawings, inaccurate cost estimates, poor co-ordination between project stakeholders, inability to standardize fabrication parameters and lack of visualization leading to not-so-informed decisions.
Drawings generated from the BIM model are consistent so the challenges of version management are quite avoidable. A large amount of time is otherwise spent in incorporating changes at a micro level, which is saved when the generation of drawing is supported by BIM.
Let us look at two of our Excelize projects to understand this better:
For a mechanical contractor in USA, we were asked to produce shop drawings for HVAC (Heat, Ventilation & Air Conditioning) from the existing design issued for construction drawings. The team produced the CAD output: a series of shop drawings showing HVAC installations.
This was achieved by building a LOD 400, 3D BIM model from the design data provided. Clash detection was performed thereafter and critical clashes were addressed through a preliminary report. Once these conflicts were resolved, a sample sheet was generated to align with the sheet standards set by the customer.
Had we taken the traditional approach, the coordination effort would have been tedious as everyone would have work in the 2D environment in isolation. While using a BIM model, each contractor could see the design of the other contractors at work and liaise suitably. This saved significant amount of time and effort. Also, with the details captured in the BIM model, the duplication of creating the details in 2D was eliminated.
Architects for state-of-the-art international school located in Alipore, Kolkata appointed Excelize to develop an interior 2D Shop drawings package for a built up area of 200,000 sq.ft. The details were developed for classroom, laboratories, libraries, activity areas, dining areas, auditorium, play areas and the entrance lobby.
2D interior shop drawings were generated from the general arrangement drawings (GA drawings), reflected ceiling plans (RCP), elevations and others shared by the customer’s team. Various packages were developed for interiors in coordination with the structure and MEP services. Flooring plans with pattern and details, casework drawings, ceiling pans and details, lighting layouts, specialized furniture details for activity rooms, classroom furniture and other such details were illustrated in the shop drawings.
All CAD & design standards were maintained throughout the project with the help of checklists and a stringent QC process.
Shop drawings drive accurate fabrication and installation through precise and detailed information and advanced visualization to clearly communicate design intent. Extraction of detailed drawings from Revit, for interiors and each MEP component, ramps up project speed and streamlines construction significantly.