Introduction
Imagine a prefabricated pipe spool delivered to a construction site that does not fit. Or, a part of ductwork which clashes with a structural beam and needs additional adjustments on-site. All this happens on the daily basis and leads to project delay, risks, and budget overruns. On-site errors in installation are one of the common problems in construction, which can be associated with lack of communication or poor planning.
Fabrication drawings are shop-level drawings that help to translate designers' ideas into concrete instructions for workshops and installation sites. As far as MEP (mechanical, electrical, plumbing) is concerned, these drawings help to fabricate a particular component according to instructions. In this article, we explain how accurate fabrication drawings are critical tools to minimize installation errors and save time/money.
What are Fabrication Drawings?
Fabrication drawings are drawings prepared by contractors, fabricators or detailers that translate the design plans into practical instructions for a workshop or site installation team. In contrast to design drawings that are conceptual, fabrication drawings are production ready. It means that all the information about precise dimensions, materials, assembly methods and tolerances is included.
In the case of MEP services, it is important to provide such information for every single component, such as ductwork, piping and supports. Therefore, fabrication drawings should be very detailed.
Common installation errors caused by poor or missing fabrication drawings
When fabrication drawings are wrong or even absent, the project is doomed. The errors become evident on the construction site where installers need to make adjustments, improvise or repeat some work. Some of the most common errors that appear due to inaccurate fabrication drawings include:
Dimensional mismatches or misfits: components manufactured to the wrong size will not fit in the place where they are supposed to be installed; thus, on-site modifications are required.
Using wrong material, thickness or spec selection: incorrect information in the drawings can lead to selection of the wrong pipe, steel, or ductwork gauge.
Incorrect connection or splice details: vague connection details can lead to weak joint, leakage, or other failures, which require rework.
Clash with other disciplines: uncoordinated drawings lead to clashes between MEP systems and structural or architectural elements; it requires last minute changes in designs.
Lack of orientation or marking: in the absence of labeling or orientation, components can be installed in a wrong way, back-to-back, upside-down etc.
How do fabrication drawings prevent these errors?
Accurate fabrication drawings can be seen as a remedy to the problems mentioned above because they help to organize manufacturing and installation.
Accurate dimensions and tolerances: by providing exact dimensions, fabrication drawings almost eliminate the need for any guesswork and ensure that components fit perfectly on the first attempt.
Clear connection and welding details: detailed instructions regarding joints, welds or connections guarantee that components will be assembled correctly and avoid failures on-site.
Detailed material callouts and Bill of Materials: comprehensive bill of materials (BOM) prevents procurement errors by listing all the parts and materials required for a project.
Orientation, labeling and match marking: clear tags, part numbers and orientation help installers to correctly assemble components; the process becomes easier and error-free.
Spool drawings and prefabrication: by breaking down a system into prefabricated spools it is possible to perform the majority of fabrication off-site, which eliminates the need in cutting, fitting and welding on the construction site.
Clash-free coordination with BIM: generation of fabrication drawings on the basis of a coordinated 3D BIM model allows detecting clashes and solving the problem virtually before the material order.
Best practices in preparation of error reducing fabrication drawings
In order to fully use the power of fabrication drawings, they need to be produced properly and consistently. Best practices need to be adopted.
Start with a coordinated BIM/3D model: use the model as the source of truth. Perform clash detection early and often to solve problems in the virtual environment prior to the fabrication.
Standardize drawing templates and notation: use consistent symbols, abbreviations and layout to make the drawing easy to understand for all the stakeholders and reduce the risk of misinterpretation.
Provide complete BOM, tag numbers and material specs: nothing is left to chance. Each component should have a tag and specification attached to it in the BOM.
Provide clear assembly sequences and match marks: include step-by-step assembly guides and match marks to show how to assemble components correctly.
Include tolerances and field-adjustment allowances: include allowable deviation and specify places where it is allowed to make field adjustments.
Perform peer reviews and QA/QC process: implement formalized reviewing and several approvals to detect mistakes at an earlier stage.
Maintain version control: use revision clouds and consistent document control system to ensure that everyone works with the latest version of drawings.
The role of prefabrication and off-site fabrication in minimizing errors
Prefabrication relies on the accuracy of fabrication drawings. It helps to manufacture components such as MEP racks and pipe spools in a controlled shop environment. It increases the quality of components and decreases the uncertainties. Besides, by using prefabrication, it is possible to accelerate on-site installation by just assembling prefabricated components like building blocks.
Implementation of fabrication drawings for MEP services
If you want to implement this practice for MEP services, you need to adopt a proactive approach.
Early involvement: MEP teams should participate in design and coordination meetings from the beginning of the project.
Develop MEP-specific standards: develop in-house standards for MEP component fabrication drawing preparation.
Train your field teams: make sure that your field teams know how to read shop drawings and encourage them to give feedback to the detailers for continuous improvement.
Measure the impact: use KPIs and cost savings
The value of good fabrication drawings can be measured. Measure key performance indicators (KPIs) such as RFIs (requests for information) related to shop drawings, time spent on rework and saved time on installation. ROI is evident when comparing the cost of detailing and prefabrication process to potential savings on site rework, delays, and material.
Conclusion
Good fabrication drawings are an irreplaceable investment into the success of your project. They serve as a foundation of error-free prefabrication and installation and lead to cost savings, accelerated project delivery and safer construction site. Adoption of standardized practices and use of BIM and CAD detailing help to eliminate potential errors virtually.
Are you ready to optimize your next project? Contact CAD Drafting Services for accurate, coordinated and installation-ready fabrication drawings.
Frequently Asked Questions
What is the difference between fabrication drawings and shop drawings?
These terms are often used interchangeably. "Shop drawings" is a broader term that covers detailed drawings produced by a contractor/fabricator, while "fabrication drawings" is a particular type of shop drawings that are focused exclusively on manufacturing instructions. In practice, they mean the same detailed and production-ready documents.
How do fabrication drawings fit into BIM coordination workflow?
Fabrication drawings are the end result of BIM coordination workflow. A coordinated 3D model is used to perform clash detection. After it is performed, the model is used for automated/semi-automated generation of fabrication drawings and spool sheets.
Can fabrication drawings eliminate all installation errors?
They cannot eliminate all errors on the installation site. A precise drawing eliminates the risk of guesswork. However, human errors, unexpected conditions on-site and poor quality control can still affect the result.
What should an MEP fabrication drawing include in order to be installation-ready?
Precise dimensions and tolerances
Complete Bill of Materials (BOM)
Tag numbers for tracking
Weld and connection details
Clear orientation and match marks
Instructions for assembly sequence
How much time/money can prefabrication using proper drawings save?
According to the industry research, better coordination between design and field work facilitated by drawings can reduce project costs by up to 20 percent. For large MEP contractors, the savings can be millions of dollars a year due to reduced rework, RFIs and faster installation. The ROI depends on the size and complexity of the project, however, it is consistent.
Who should prepare and approve fabrication drawings on a project?
Drawings are typically prepared by the fabricator or specialist detailer. They are reviewed and approved by the main contractor, engineers and designers. BIM coordination teams also participate in the process of ensuring that drawings are clash-free prior to issuing