Flexible Retail Center Design - Plumbing & Fire Protection –

The design for plumbing in a retail shell building is typically straight forward; however there are several considerations which should be reviewed when designing the water, sanitary, fire protection and gas (where applicable) systems for the overall center.

Water - When considering domestic water service, it is important to bear in mind the type of tenants that will be served. Depending on the local pressure and water flow, a typical restaurant space could require a 2” line as opposed to a retail space which might only require a ¾” line as long as tank type toilets are utilized. The most flexible design involves working with the developer to consider a worst case scenario as far as water usage is concerned. This worst case can be utilized to size the overhead pipe size that can be run with a series of 1” and 2” taps/valves to allow for ease of future tenant connections. Typically as a cost saving measure, deduct meters are installed under the tenant installation, as all of the valves may not be utilized.

Sanitary - Sanitary waste systems for most retail facilities are very basic with a 4-inch building sanitary main being typically sufficient. There are three basic options for sanitary design. The first is to run under-slab the entire length of the facility with the sanitary main providing cleanouts only at code required locations. This pipe can be run in either a 10ft “leave-out” (no concrete slab) in the rear of the space or it can have the slab poured completely over it. While this approach has an initial low cost, it is often more than offset by slab cut/patch and longer tenant construction timeframes.

A second approach to sanitary, if the landlord has a good idea of the types of tenants they will be attracting, is to run the entire length with the main sanitary and providing restroom stubs in a few key locations for possible tenants who need to get in their space quickly.

Once again, food service facilities will have additional requirements - specifically, the need for a grease interceptor and related grease-laden waste piping. Unless a specific tenant is known, grease interceptors are not typically designed under the shell package. While there are many ways to handle the grease waste, the most flexible approach if a space has the potential to be a restaurant is to provide two stubs out of the facility in case the grease interceptor must be located outside of the space.
Fire Protection - Typically under the shell design a main riser will be installed and in some cases a line will be installed along the entire rear of the facility. The logical question is how big should the line be (both the incoming and the overhead). More than any other aspect of the design, this is dependent upon the available flow and pressure from the local utility. Once the information is acquired from the utility, the sizing of both the main entry and the main riser size can be calculated based on the size of the spaces and there intended use, or worst case usage if tenants are unknown.
Gas – When gas is available at a site there are two primary design decisions that must be made with regards to gas service for a retail shell building. The first is the overall requirements of the facility and the second is distribution of gas piping. As noted with water service above, based on the worst case anticipated needs of the developer, the main gas service can be sized. Ensuring that enough gas is brought to the site is critical as acquiring additional gas after pavement is down can be extremely expensive. The distribution of gas piping is dependent upon the selections made during the HVAC design phase. If gas is needed in the shell space, there are two options for gas piping. The gas pipe and associated metering can either be all sized for retail tenants, all for restaurant tenants, or a combination based on the developers expectations for each space.

As you can see, one set of design parameters will not fit the plumbing requirements of all retail centers; however, a little planning ahead can increase the facility flexibility for both the developer and the future tenants.

Flexibility? So flexibility is dependent upon your perspective. One extreme is no utilities provided, which is a low upfront cost approach at the sacrifice of tenant build-out timing and possible damage to the integrity of your building. While the other extreme provides utilities as if spaces were almost ready to occupy – this approach costs more upfront and limits flexibility but it does speed up tenant occupancy. The conclusion being there is no “one size fits every retail center” solution; however, a careful analysis of each of these components will lead to the most flexibility for your next center.

Trent Beighle, PE is the president of PE-Services. For further information contact Trent at trent@pe-services.com or Roger Butler, PE at roger@pe-services.com.

Flexible Retail Center Design - Electrical Systems–

There are two main considerations to review when beginning the electrical portion of a retail shell design. The primary consideration is the Electrical Service design for the entire facility as well as the individual future tenants. While there are many lighting decisions to make which are primarily preference driven (parking lot lighting, accent lighting, etc.), the emergency/egress lighting is a code consideration which must be evaluated throughout the shell design phase.

In order to create as much flexibility as possible, the main service design will vary widely based on the building size. For larger centers, this may be accomplished through a package switchgear unit or for a variety of centers it might include a wireway with a series of disconnects and meters. As noted with other utilities, the main focus of this portion of the design should analyze the worst case usage. The equipment size is not always reflective of the worst case, but in order to maximize flexibility the secondary conduits from the transformer should always be provided based on the best analysis of the load for the entire facility. The primary difference is that while the package switchgear cost considerably more, in larger applications the space requirements can be significantly less than the wireway option.

Once the main service is designed, consideration must be given to conduit, wire, and panel distribution for the future tenant spaces. Should panels be installed in each space or should we just install conduits. If we decide to install conduit only, what size should we install. The answers to the questions will be based on the confidence the developer has in their knowledge of the future tenant types as well as the necessity to get tenants in the center quickly.

The least flexible tenant service design, although the quickest for future tenants, is to size the panels based on the intended use of the space and provide the meter, disconnect, and panel under the shell package. There are two other approaches which involve empty conduits for future spaces – these conduits can be run under the slab or to maximize flexibility they can be run overhead so as to allow conduits to easily be shortened or extended as tenants require. While not as flexible as the overhead conduits, the conduits underslab can be increased in size to add flexibility while not adding the same costs to the project as overhead metal conduit will. These same alternatives need to be considered for telephone/data conduits to each tenant.