Introduction

There is one situation that every project manager in the construction industry experiences. A prefabricated duct section is delivered on-site, and it does not fit. The hangers are slightly off because of several inches’ margin. The connection points do not align with the structural steel. The situation looks like something simple enough; however, it becomes complicated since it needs several hours of rework and days of delays.

Such issues with installation are not only inconvenient but also quite costly. Rework causes huge cost overruns, and most of them are associated with inaccurate fabrication drawings.

A fabrication drawing, sometimes called a shop drawing, is a document that provides a detailed set of specifications about how the components will be manufactured, assembled, and installed. Fabrication drawings differ from design drawings because of the level of details. Fabrication drawings for MEP (mechanical, electrical and plumbing) services are even more specific. The main purpose of such drawings is to create accurate instructions for the fabrication of prefabrication parts in the shop environment before they are installed on-site. Thus, it can be concluded that accurate fabrication drawings are extremely helpful for project managers, fabricators, MEP contractors, and BIM coordinators. Below you will find out why.

 What are Fabrication Drawings?

Fabrication drawings are technical drawings that provide detailed information about the manufacturing process of the building components. These documents are required to manufacture components in a shop environment before their installation.

The difference between fabrication drawings and design drawings is that while the latter shows what kind of building should be created, the former indicates how it should be built. The key features of fabrication drawings are dimensions, materials, tolerances, connections, assemblies. Types of fabrication drawings include shop drawings, detail drawings, assembly drawings, as well as piping and ductwork drawings, fittings, and structural steel component drawings.

In general, it is important to distinguish between fabrication drawings and construction or installation drawings. Construction drawings are used to direct the construction process and show how the systems should be located. However, fabrication drawings are the guidebooks for the shop floor. They show what to cut, bend, weld, and how to assemble.

The typical flow for creating fabrication drawings is the following one: the designs and ideas are developed by architects and engineers, and later translated into shop drawings by detailers. Then, fabrication drawings are used by fabricators to manufacture parts that will be installed on-site by construction crews.

 Key Elements of Accurate Fabrication Drawings

Accuracy in fabrication drawings is impossible without details. A good fabrication drawing should include all necessary elements, and leave no room for doubts.

First of all, it includes dimensions, tolerances, and material specifications. It means that every dimension should be marked precisely, and tolerance should be indicated too. Every material should be specified – its type, grade, thickness, finish, and all the rest.

The second important element is connection details that indicate how components should be joined together. For example, fabrication drawings should show welding symbols, bolt sizes and patterns, splices and anchors. In addition, for MEP systems, support and hanger information with spacing and load ratings should be provided too.

Finally, there is a Bill of Material (BOM), part numbering system and cutting and bend/cut list for ducts and pipes. In addition, fabrication drawings include revision stamps and approval marks to ensure that all drawings were checked and approved.

 How Fabrication Drawings Improve Installation Accuracy

Eliminating the Guesswork

The most obvious advantage of the fabrication drawings is that they eliminate guesswork. Since they include all required dimensions and connection details, all parts are manufactured exactly as it should be. When installation crews get parts designed to fit together, there is no need for corrections, since everything is already done in the shop environment.

Minimizing the Field Rework

It goes without saying that field rework costs a lot of money. Every hour spent on rework adds to the cost of the project and makes it longer. However, accurate fabrication drawings guarantee that prefabricated parts are manufactured correctly and do not require rework.

Coordination

In today’s world, modern construction projects involve numerous trades that work in the same area. Therefore, they need to coordinate ducts, pipes, conduits and structural steel. Fabrication drawings integrated with BIM (Building Information Modeling) allow to detect clashes before any material is cut. Clashes between MEP systems and structure can be detected in advance using digital models, not in the construction site.

Standardization

Consistent fabrication standards and shop practice result in repeatable and accurate assemblies. Standardized templates, layer naming conventions, symbols, and part numbering allow for everyone to understand the drawings in the same way.

Better Logistics and Sequencing

Prefabricated modules and their labeling and part numbers simplify the installation process. People who work on-site know exactly what each piece is and when it should be installed. This makes sequencing easier, and site congestion decreases.

 Role of Technology in Accurate Fabrication Drawings

  • Modern technology has changed the process of fabrication drawings creation from manual drafting to precision engineering.
  • CAD, BIM and 3D modeling became the standard today. These technologies allow to perform clash detection, precise dimensioning, and visualization, and it is impossible to achieve with 2D drawings. With 3D modeling, the components’ interconnections become visible, and potential clashes can be detected even before fabrication starts.
  • Modern CNC fabrication equipment works according to the CAD-to-CAM workflow that relies on the accurate shop drawings. The drawings made with the help of BIM software can be transferred to the machinery to perform fabrication tasks automatically and without any errors.
  • Moreover, fabrication drawings are easy to edit and approve digitally. Instead of mailing the physical drawings to each team member, they can collaborate in real time commenting, reviewing and approving drawings immediately.
  • Besides, scan-to-fabrication and laser measurement technologies are used to close the gap between existing conditions and the new construction. With laser scanning technology, an environment of the renovation project can be measured with millimeter accuracy. This allows adjusting the fabrication drawings according to the as-built condition.

 Best Practices for Producing Effective Fabrication Drawings

Early Coordination

Fabricators should be involved in the design process. It is the most effective way to make fabrication drawings accurate and buildable. Fabricators can bring their experience in manufacturing capability and material availability to the table.

Standardized Templates

All the projects should use the same templates, layer naming convention, symbols and part numbering. It will allow avoiding misunderstanding and accelerating the training process for new team members. In addition, standardized template ensures that there will be no information overlooked.

Explicit Installation Notes and Tolerance Tables

All fabrication drawings should contain explicit notes and tolerance tables. This information will be useful for those who are responsible for installation. Moreover, these notes and tables will show acceptable variations, assembly sequence, and some special installation instructions.

Internal Quality Assurance and Review Cycles

Multiple reviews should be performed during different stages of drawing development. However, it is not recommended to submit unchecked drawings for approval. Forgetting to send drawings for checking can result in multiple review cycles. Drawings should be checked and fabrication-ready before approval.

Revision Management

It is very important to keep fabrication drawings updated with revisions and keep clear revision history. Feedback loops should be included in the drawing set for future improvement. Good version control is essential; otherwise, outdated drawings on-site can ruin everything.

 Specific Considerations for MEP Fabrication Drawings

  • MEP services have many aspects that require special consideration in fabrication drawings.
  • For example, in order to manufacture ducts and piping, there should be precise information about dimensions, fitting specifications, and hanger spacing. All bends, tees, and transitions should be indicated accurately. Spool drawings of pipes show how pipe assemblies should be manufactured and installed.
  • The location of valves, dampers, access panels should be determined to ensure accessibility in the future.
  • Service penetration coordination is one of the most common problems. Ducts, pipes, and conduits should go through structural steel elements. Penetration locations should be coordinated with structural drawings to avoid any clashes.
  • In addition, modular MEP assemblies become more and more popular, and they require accurate fabrication drawings to ensure that all modules will fit together on-site.
  • Code compliance should be taken into account too. The fabrication drawings should contain all codes and manufacturer requirements. This is especially important for fire protection, life safety, and energy efficiency systems.

 Performance Measurement: KPIs and Outcomes

  • How do you measure the effectiveness of your fabrication drawings? Pay attention to these KPIs:
  • Reduction in rework hours on-site: You can track how many hours are spent doing rework on the site compared to previous projects when improved fabrication drawing practices were not applied yet.
  • Fewer RFIs: Well-prepared set of fabrication drawings should answer all possible questions in advance, hence less RFIs.
  • Installation time savings: Measure how much time is taken by installation of MEP systems. Faster installation is the sign that your fabrication drawings are effective.
  • Lower costs: Change orders and field modifications tracking will show how lower costs your fabrication drawing approach provides.
  • Scheduled on-time installations: It guarantees that the whole schedule of the project is predictable.
  • Gathering these KPIs can be done through field reports, QA checklists, BIM model changes, and change orders tracking. Data will show the efficiency of your investment into accurate fabrication drawings.

Conclusion

Fabrication drawings are not only the drawings but also the key factor of project success. Precise, detailed drawings eliminate ambiguities, reduce rework, improve coordination and speed up installation. They bridge the gap between design intentions and its realization. Fabrication drawings allow to produce parts, which fit perfectly on the site.

Benefits of good fabrication drawings are evident – reduced costs, improved schedules and low risks. The path to achieve them is clear too – involve fabricators early, make good quality MEP fabrication drawings and use digital workflow to guarantee their accuracy at all stages.

When fabrication drawings are done right, installation is the assembly. And the assembly leads to profitable and timely project completion.

Frequently Asked Questions

What is the difference between fabrication drawings and shop drawings?

These terms are often used as synonyms. Shop drawings are a kind of fabrication drawings, which describe components to be produced in the shop. They both provide all necessary information for fabrication and installation.

How do fabrication drawings reduce installation rework and costs?

Accuracy of fabrication drawings guarantees that the components are fabricated right from the first try. Perfect fitting of parts on site eliminates any need in rework. It saves labor costs, material resources and schedule.

What should be included in an MEP fabrication drawing?

It should contain dimensions, materials, tolerances, connection details, hanger locations, valve and access points, and the bill of materials. Also, routing of duct and pipe, bend details and penetration locations should be included in the MEP fabrication drawing.

When should fabricators be involved in the design process?

Fabricators should be involved early in the design process, during design development stage. In this way, they have a chance to give feedback about manufacturing requirements, availability of material, cost-effectiveness and other issues related to fabrication drawings.

How does BIM increase the accuracy of fabrication drawings for MEP services?

With BIM technology 3D modeling, clash detection and dimensioning become possible. Integrated models provide coordination of MEP systems with the structure and architecture of the building and prevent clashes, which cause rework. BIM technology also enables CAD-to-CAM workflow for automated fabrication.

How do I ensure that fabrication drawing is accurate before starting its fabrication?

Thorough internal QA checking of the drawings should be performed prior to their submission for approval. After the approval, the control of revisions should be ensured. Field verification by laser scanning can help to detect possible discrepancies before starting fabrication of parts.

Ready to Improve Your Installation Accuracy?

Camellia Buildtech specializes in providing BIM and fabrication drawings for MEP and structural services. We are ready to provide you with professional assistance in preparation and checking of accurate and coordinated drawings. From clash detection to shop drawings production – we provide all the necessary expertise.

Contact us today to learn more about our BIM and fabrication drawings service Let us help you bring precision to every project.