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To be or not to be Structurally sound....that is the question!

Updated: Nov 11

By: Karl Travis, RID and partner at Hager Design International Inc.


As a Registered Interior Designer (RID) in the field of restaurant interior design, we deal with all aspects of the build out of restaurants. We do not just design pretty restaurants and position things for what looks best, there is a lot of considerations that must be addressed when designing the whole infrastructure of what makes a restaurant tick.

Having worked in restaurants myself, I am passionate about designing a fully functioning and profitable restaurant. Whether a Quick Serve Restaurant (QSR) or a regular franchised or independent restaurant. Front of house and back of house, we cover it all! We deal with all consultants, mechanical, electrical, structural and sometimes architectural. Our principal is BCIN accredited, which means we know the building code extremely well and apply for building permits on behalf of our clients on a regular basis.


During our design process, we always come across some issues that were not anticipated for the future use of the space. Like for instance, when working with the mechanical requirements of a QSR we need to add a Make-up air unit (MAU) to the roof, and the weight of the unit (plus the snow load in some areas) may impact the structural stability of the building. The landlord has not allowed for this in the construction of the building hence the need to engage a Structural Engineer to ensure that the unit (weighing 1500 lbs or more) will sit securely on the roof without collapsing.

To reinforce the importance of engaging a Structural Engineer for their MAU & RTU (roof top unit) in the early stage of the project, here’s the excerpt of the email I sent to the building owner.


“With regards to structure, it would be best if a structural engineer would be contacted for the placement of both the new RTU and MAU locations. Simply installing structural supports without a structural engineer’s input may not fly with the City nor hold up structurally.


When a roof top unit of any sort is added to an existing structure, the engineer provides the calculations based on the size and weight of the unit along with the appropriate placement on the roof in relation to the joists. As well, the engineer considers the other equipment located on the roof including wind or snow loading requirements.


The drawings that are provided by the mechanical engineer do not take into considerations any structural calculations, only indicates the mechanical engineer’s preferred location and requirement for separations by code. In particular, the KEF (Kitchen Exhaust Fan) cannot be located within 10 feet of any air intake from adjacent RTU’s or the MAU.


Therefore, the structural engineer will need to consider the mechanical engineer’s preferred location and ensure that it is ok or do the following:

  1. First, if those locations work, the AHJ (Authority Having Jurisdiction) requires a letter indicating this. The AHJ may require new drawings especially if a new RTU is being placed.

  2. If the units’ placements can be slightly adjusted and does not require structural support added, then there is no added cost and time of adding supports.

  3. If the units’ placements need to be adjusted substantially, the mechanical engineer needs to be consulted if the new locations are acceptable in relation to the ducting runs below.

  4. If the structural engineer’s suggested new placement is different than the mechanical engineer’s placement and new structural support is required, the structural engineer has to create a drawing that will advise the contractor on the size, location and type of support that is required.

Randomly placing heavy equipment on the roof can cause problems and damage to the roof structure if not designed properly as well becomes a life safety and liability issue.

Here is a capture of a drawing provided to us by a structural engineer (Gerrits Engineering in Barrie, ON) for a project. In this case, the joists were steel.

In the case of this project, if the outlined suggestions would not have been followed, this restaurant would not have been allowed to open and the goal is obviously to achieve that in record time. Hiring professionals to deal with not just the interior design that results in a great Return on Investment but focuses on health and safety that also includes structural in situations like this, is critical for a successful project that can get opened with a permit in record time earning money for the owner.

Karl Travis is a RID and a Partner in Hager Design International Inc. and also heads the Restaurant Interior Design Division. Karl can be reached at info@hagerinc.com

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