Tenant Improvements – Does the Existing Structure Need to be Reviewed or Upgraded?Mar 24 2015 · 0 comments · Nishkian Chamberlain, Tenant Improvement ·0
Building owners and architectural consultants lose many a night’s sleep wondering how much they can alter the existing building space and structure to accommodate and attract new tenants before they are slammed with the Department of Building and Safety’s request to have the “Existing Structure Reviewed or Upgraded.” In a previous blog post, a review of the requirements for upgrading existing structures was discussed with a focus on repair due to unexpected building damage. In this post we focus on planned tenant improvements, a quick review of Code requirements, and a short project example.
Tenant improvements (TI’s) are one of the most common projects in construction today. Often renovations, upgrades, or even additions to existing structures are more enticing for Owners than building from the ground up. With limited budgets and tight timelines, sometimes tenant improvements are the only answer for “new” space. TI’s can work within tight budgets by reusing much of the existing structure or at a minimum within the framework of the original building. They also save time by eliminating some of the overall building construction as well as simplifying the permitting process with fewer permits not to mention fewer fees to be paid.
But when the decision has been made to improve or add to an existing structure, how is one to know when an upgrade to the existing structural elements or entire building will be required? Common questions include:
- Is this a bearing wall and can I remove it?
- We are adding a new stair between floors and opening up the slab. Do you need to analyze the whole building?
- We are adding a new A/C unit to the roof. What do I need to do?
- The storefront is being replaced. No other changes are being made. Would this trigger any mandatory structural improvements?
Working with and designing for existing structures is inherently different than with new buildings. These structures were designed to older Codes and often have materials and/or construction techniques that are different than how we would build today. For this reason, existing structures have a separate section of the Code to address additions, alterations, and repairs which is found in Chapter 34 of the International Building Code (IBC) and is adopted by most states. This section lays the foundation for dealing with existing buildings.
For any TI project, the addition or alteration must comply with the requirements of the Code for new construction (unless an alternate method of compliance is accepted by the jurisdiction). The existing building structure with the new alteration or addition must be shown to be no less conforming than it was prior to the addition.
Two key structural provisions of Chapter 34 include:
- Structural Elements carrying gravity load: Any existing gravity load-carrying member to which an addition or alteration increases its load by more than 5% or decreases its load carrying capacity by more than 5% shall be strengthened/altered as needed to carry the increased load in accordance with the Building Code for new structures.
- Structural Elements carrying lateral load: Any existing lateral load-carrying member to which an addition or alteration is implemented and its demand to capacity ratio increases by more than 10% compared with the addition or alteration ignored shall be strengthened/altered in accordance with the Building Code for new structures.
Beyond these two provisions it is critical to ensure changes to the structure are not creating other irregularities or unwanted structural performance in the building. Each TI project is unique and must be reviewed for its individual changes and effects of the specific structure.
One recent project (names withheld to protect the innocent) involved renovations to an existing two-story concrete building built in the late 1920’s. The TI scope involved a complete gut of the existing interior of the building and the addition of a new main staircase and 2nd floor opening, new exterior wall openings, new rooftop skylights, enclosing of some wall openings, infill of an old non-conforming staircase and addition of a small mezzanine.
An analysis of the building was undertaken to review the change in lateral performance with respect to the proposed new floor and wall openings. A preliminary analysis revealed that the new wall openings triggered a full building upgrade requirement due to significant changes in stiffness of the existing buildings structural elements and expected performance of the entire building during a major seismic event. With a tight budget, that did not include provisions for a full building seismic upgrade, a creative approach to accommodate the proposed wall and floor openings was needed.
The Nishkian Chamberlain engineers in collaboration with the building owner and the design team, obtained approvals by the local building department to modify the existing structural system in such a way that the new wall openings did not alter the demand to capacity ratio by more than 10% in any of the remaining wall structure. This focused the improvement on the alteration without requiring the full building to be upgraded due to the wall opening on one side of the building. The project resulted in a win for the Owner utilizing a tenant improvement on a 1920’s building to develop a virtually “new” building without the cost of a “new” building.
Nishkian engineers have established themselves as creative, collaborative problem solvers with extensive experience in dealing with complex tenant improvement projects involving additions, alterations, and repairs. Should you have any questions about an upcoming or ongoing project, do not hesitate to contact any of our offices. You can also send an email directly to Craig Chamberlain at email@example.com.