Accurate, Complete Shop Drawings a Plus on Metal Roof and Wall Panel Projects

A shop drawing is a drawing or set of drawings produced by the contractor, supplier, manufacturer, subcontractor, or fabricator on a metal roofing or wall panel project.

It is an essential part of any project and the quality of the drawings can influence whether a project will be done correctly to specification, whether there will be legal issues down the road about meeting spec and even whether the job will be completed on schedule.

Shop drawings are not produced by architects and engineers under their contract with the owner. The shop drawing is the manufacturer’s or the contractor’s drawn version of information shown in the general contractor’s construction documents. It is drawn to explain the fabrication and/or installation of the items, in this case, metal roofing or wall panels, to the contractor’s installation crews. Unlike an architect’s drawing, a shop drawing’s primary emphasis is exclusively on the particular product or installation, unless roofing and wall panel materials must be integrated with other materials.

The shop drawings should include information for the architect to compare to the architectural specifications and drawings. The shop drawing gives the architect the opportunity to review the fabricator’s and/or installer’s version of the product, prior to fabrication. Attachment of manufacturer’s material specifications, “catalog cut sheets,” and other manufacturer’s information like independent testing results and installation instructions should accompany these drawings. Manufacturers like Englert have all of this information readily available at their company websites so it can be downloaded onto a disk or easily printed out for attachment to the drawings. Some fabricators and manufacturers will provide symbols, data, or instructions concerning installation. This can include a list of other materials, such as fasteners or adhesives, appropriate but not included for the product.

Special care must be taken by the contractor to measure and verify dimensions. It’s important that all the details of the materials and their specific installation be planned out on the shop drawing so that when a subcontractor’s crew arrive s at the work site they know specifically what is required for that roof. If not, and they have questions, for example, about cap flashing or the kind of joints that are needed, the situation arises where the job has to be designed on the spot, while a four-person crew working at an hourly wage sits idly by.

Some roofing and wall panel contractors have in-house staff to do shop drawings. Others will hire a draftsman to do them for a specific job or call on a panel manufacturer like Englert to do them as an added service.  Depending on the size of the project, the time to develop shop drawings can range from two to four hours up to 120 hours.

The general contractor has a timeline schedule for construction and the request for shop drawings appears on that schedule with a requirement to the roofing or wall panel installer to provide them usually from two to four weeks. If the drawings are sketchy, the timeline can be affected.

The quality of the final drawing hinges on the subcontractor’s ability. Some can be pretty rough and others can be very sophisticated. The irony is that some contractors really know the products they are working with and are excellent and innovative in installing them. But when it comes to the drawings, they simply can’t present or draw well. Consequently, those drawings will be “redlined” by the architect and kicked back to the contractor to provide more detail and explanation.  Shop plans are generally a long lead item in the construction schedule—part of the real-time sequence of activities on a project. Kicking them back to the contractor to be fixed can easily delay the sequence of activities on the project.

Ultimately, the architect is responsible for changes in these drawings and should have the opportunity to analyze any modifications. It is imperative that the fabricator and/or installer address any areas that need clarification with the architect before the installation begins. This attention to modifications and the quality of the shop drawings can avert legal issues down the road. An architect may have an issue with the details the contractor provided on the roof or wall specifications. The contractor should be able to point specifically to the shop drawing as proof he fulfilled the architect’s initial requirement, thus effectively closing the door on any disclaimers. Otherwise, if there is a dispute because the information is unclear or missing, the architect controls the purse strings and the contractor may have difficulty getting paid.

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