The addition of a custom glass entrance is an excellent way to revitalize an existing building. Whether it’s a point-supported glass vestibule to manage traffic and space conditioning within the building, or a structural glass façade to attract more visitors, the aesthetics that come along with custom glazing systems can have a big impact. Critical first steps in the successful completion of a custom-design retrofit, is to coordinate with the engineer of record and engage in investigative work to determine the existing structures, materials and conditions.
When completing a renovation on an existing building, detailed as-built drawings seem to be the most efficient way to uncover what is hidden by various exterior cladding systems. The trouble is, these drawings are not always available or accurate and up to date. For instance, older buildings can undergo multiple renovations without updates to as-built drawings. Unfortunately, this lack of information can lead to uncertainty during the bidding stage and preliminary design stages of subsequent construction.
If accurate as-built drawings are not available, the strategy to obtain an accurate determination of existing conditions is based on access.
– Field dimensions: In cases where the area under renovation is accessible, simple field dimensions can often provide what is needed for renovation design and planning.
– 3D scanning: Scan technologies such as laser scanners allow for the creation of a detailed “point cloud” of information of existing conditions that can be converted into detailed 3D models of various formats. Building scans are particularly helpful when the project conditions are too large or inaccessible to measure manually.
– Demolition / coring: To avoid issues with unforeseen conditions later in the project, there is always a certain level of physical demolition and research that should be done to accurately document what is already in place. Coordinating with the engineer of record is a great way to get the background information and set the expectations for the demolition work. Keeping the physical demolition to a minimum is a key component, peeling back just enough to allow for access. Field measurements can then be pulled to set the parameters of the design, quantify materials, determine anchor points, etc.
The following project examples include a situation where the position of structural members was determined well after the start of construction (1350 Eye Street), and one where a laser scan was performed prior to material fabrication to insure proper coordination/fit of new system on existing structure (MIT Kresge Auditorium).
1350 Eye Street
Bellwether completed a renovation to an existing building in Washington, DC consisting of an exterior glass wall with an integrated interior vestibule. During the preliminary design stages, the structural steel anchorage was believed to be within 12” of the finished ceiling based on original building architectural and structural drawings. This proximity of structure called for a simple face-mounted anchor.
When the GC proceeded to core out the existing finished to expose the structure, well after the start of material fabrication, it was discovered that the structural steel anchor point was over 3’ from the finished ceiling surface. Bellwether coordinated with the building engineer to develop a steel kicker/anchor that could handle a significant increase in torsional forces applied to the tall anchor.
Bellwether then analyzed the ability of the entire structure (wall and vestibule) to handle the imposed loads as a coordinated system. To reduce the torsion on the tall kickers and existing structure above, Bellwether used the stability of the base glass vestibule and walls to nullify the cantilever of the suspended fins. The end solution saved the installer, GC, and building owner money by looking at the complete picture and engineering a relatively low cost kicker versus finish materials such as extended glass fins or a more extensive supplemental steel support structure.
MIT Kresge Auditorium
Bellwether recently completed a renovation project at the historical Kresge Auditorium on the MIT Campus in Cambridge, MA. The main objective was to replace the existing aluminum skin system with a new laser fused stainless steel system while retaining the original curtain wall design, shapes, and dimensions.
The new system was to mount to the existing interior steel mullions. To accommodate the existing steel dimensions and tight tolerances of the new material to be fabricated, a laser scan was completed to ensure accuracy in the relationship of new to old when the pre-fabricated material arrived on site.
Materials were delivered pre-fabricated and pre-finished to accommodate efficient installation and a tight project schedule. The existing steel mullions outside tolerance were straightened and refinished, allowing the new system to fasten directly to the existing structure with minimal site work.