Delegated Design for Glazing: Why Waiting Until Installation Defeats the Purpose

For glazing contractors, engineering can sometimes look like another project cost: calculations, stamped drawings, shop drawings, revisions and submittal reviews.

That makes it tempting to push engineering later in the schedule—or, on some projects, try to get by with less of it.

The problem is simple:

Engineering performed after major decisions have already been made cannot protect those decisions nearly as well.

Delegated design should do more than satisfy a specification requirement. Used properly, it helps confirm that the glazing system, attachments and supporting structure will actually work together before expensive materials are fabricated and installed.

Delegated Design Is More Than a Closeout Requirement

Glazing specifications commonly require delegated-design submittals supported by engineering analysis prepared by a qualified professional engineer.

Depending on the project and jurisdiction, delegated-design documents may also be treated as deferred submittals. In those situations, approval may be required before the delegated portion of the work is installed.

But even when enforcement is inconsistent, the practical risk remains the same:

Installing an unverified glazing system puts the contractor in the position of discovering engineering problems after the least expensive solutions are gone.

A connection that is easy to change on a drawing can become expensive once aluminum has been fabricated, anchors purchased, glass ordered or crews mobilized.

Engineering May Be 2–5% of the Glazing Cost. The Decisions Affect Much More.

As a rough project-planning range—not an industry-standard fee—engineering and drafting might represent approximately 2–5% of the glazing package on many projects.

The percentage can increase significantly with complexity, including:

• Structural glass

• Glass fins

• Point-supported systems

• Complex curtain wall

• Canopies and skylights

• Large sunshades or architectural features

• Difficult anchors and attachments

• Significant building movement

• Unusual supporting structural conditions

Looking only at the engineering fee misses the larger issue.

That relatively small portion of the project can influence the selection, fabrication and installation of a much larger portion of the glazing package.

Where the Real Cost Appears

Consider what happens when engineering is completed late and discovers that:

The attachment doesn’t work.
The specified anchor may not have adequate capacity, edge distance or access.

The supporting structure isn’t where everyone assumed it would be.
Steel, concrete, cold-formed framing and embeds may differ from the architectural assumptions.

The system needs to accommodate more movement.
Building drift, deflection, thermal movement or differential movement may require changes to connections or joints.

The glass or framing needs to change.
A member, glass lite, reinforcement or connection may need greater capacity.

The architectural feature creates loads nobody fully addressed.
Fins, sunshades, louvers, canopies, parapets and specialty façade elements can introduce significant loads and eccentricities.

Every one of those discoveries is easier to address before materials are purchased.

A Better Approach: Pre-Engineering and Design Assist

Instead of viewing engineering as something that happens after award, glazing contractors can use targeted Pre-Engineering or Design Assist earlier in the project.

The objective isn’t necessarily to complete every final calculation before the project is sold.

It is to answer the important questions early enough that the answers can still influence the job.

Better Material Orders

Early engineering can help verify member sizes, glass assumptions, reinforcement, anchors and attachment concepts before long-lead materials are released.

That can reduce the risk of buying the wrong material—or discovering later that additional material is required.

Better Sales and Estimating Assumptions

Estimators frequently have to price projects with incomplete information.

Pre-engineering gives them another technical resource for evaluating unusual spans, attachment conditions, glass sizes, structural requirements and system limitations before those assumptions become contractual obligations.

Better Support for Project Managers

Project managers learn enormously through experience.

But they shouldn’t have to learn every structural lesson through a field problem.

A façade engineer working alongside a PM provides another set of experienced eyes on RFIs, details, interfaces, substitutions and difficult structural conditions.

That creates valuable on-the-job technical development while protecting the project at the same time.

Earlier Problem Identification

Perhaps the greatest value is simply seeing problems sooner.

Experienced glazing engineers and drafters look at projects differently. They routinely evaluate:

• Load paths

• Attachments

• Building structure

• Glass limitations

• Aluminum capacity

• Structural movement

• Edge distances

• Fasteners

• Reinforcement

• Fabrication constraints

• Installation access

• Coordination between trades

The goal isn’t to find fault.

The goal is to find solutions while there are still inexpensive solutions available.

Don’t Engineer the Paperwork. Engineer the Project.

Glazing engineering should not be treated as documentation that needs to be produced eventually so somebody can check a box.

Its highest value occurs much earlier.

Done at the right time, engineering and drafting can help contractors make better estimates, order materials more confidently, train and support project managers, coordinate with the building structure and discover problems before those problems reach fabrication or the field.

The question shouldn’t be:

“How little engineering can we get by with?”

A better question is:

“How early can we use engineering to protect the rest of the glazing package?”

JEI Structural provides Specialty Glass and Facade Consulting, Engineering & Drafting, including delegated design, pre-engineering, design assist, glazing engineering, structural glass engineering, curtain wall engineering, shop drawings and specialty façade engineering.

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JEI Structural is a nationwide specialty glass and facade consulting, engineering and drafting firm specializing in glass and glazing engineering, curtain wall and storefront systems, structural glass, glass railings, architectural metal systems including louvers, sunshades, fins and canopies, cladding and panel systems, delegated design, building envelope consulting, shop drawings, constructability reviews and third-party facade reviews for glazing contractors, general contractors, architects, owners and manufacturers.