By Charles Plunkett
If you’re developing self-storage, there are many reasons to consider building a multi-story facility. First, a multi-level project can allow you to develop on a smaller site, which can be important in areas where land is extremely expensive or you’re only able to acquire a limited plot. This type of structure also allows you to infill an urban site such as a downtown property in a major metropolitan area.
A facility with multiple floors also allows you to offer higher security. For example, you can restrict access to a floor to only those tenants who rent units there. This is ideal for properties that offer more than traditional storage, such as records or wine storage.
Through their height, multi-story facilities even create their own “signage.” This can include the use of attention-grabbing building materials, or a showcase of roll-up doors through windows. This immediately lets prospective tenants know the building is for self-storage.
In addition to the many benefits of a multi-story self-storage facility, there are important factors to consider, such as zoning, structure type, foundation and building codes. Let’s take a look at each.
Zoning
One of the first issues to resolve is your site’s zoning. The need for a zoning change or special-use permit can be a huge hurdle. You’ll often need a highly attractive project to gain municipal and community support for the required entitlements.
Consider any local height restrictions. These can come in the form of a deed restriction on the property, ordinances imposed by the city, a restriction due to proximity to an airport, or simply one that develops as part of the rezoning process. In the case of rezoning, neighbors can demand a height or story restriction in exchange for their support of the project.
Structure
There are essentially three types of multi-story buildings:
- A slab on the ground with the multiple levels going up
- A basement (or even multiple levels below ground) with additional levels extending above ground
- A split-level building
In many cases, split-level can be the most cost-effective construction method. It works especially well on a sloped site. You build a retaining wall at the back side of the building to hold back the earth, with partial retaining walls at each end of the structure. Tenants can enter the first level on the front side, or drive up and around to the back to enter at the next level. This can help alleviate the need for massive site work, i.e., adding or removing soil to level out the site. If a split-level is only two stories high, you can usually eliminate the need for stairs or elevators, which results in huge savings.
Foundation
You have to consider constructability issues related to the site. This can include the proximity of utilities such as sewer and water. One of the bigger potential problems is soil condition. The saying “A house is only as good as the foundation on which it’s built” rings true. I’ll take it a step further and say, “A foundation is only as good as the soil on which it sits.”
Stable soil is an important component in any building project, but it’s even more significant in a multi-story project due to the added weight of the building. Movement or settling in the soil is magnified in a multi-story project, and problems can result.
If you’re building a basement, this presents an entirely new set of challenges, including the need for concrete retaining walls, which hold back the earth around the portion of the building that’s below ground. They must be properly waterproofed on the exterior so no moisture can seep into the building.
You also need to install a drain mat around the exterior of the retaining walls to direct any moisture to the bottom of the wall, which is then collected in a French drain system. This drain will gravity-flow the moisture to a collection box and pump it to the surface or, if possible, continue the flow to where it can be exposed at a lower grade and surface-drain onto the ground or a storm-water system.
Building Codes
In the past, builders could use the typical light-gauge steel framing that’s customary in the self-storage industry for buildings up to four stories tall. But building codes have changed. Where there were previously several building codes under which cities could choose to operate, these have been consolidated into the International Building Code (IBC). Most cities have adopted the IBC 2012. Under this version of the code, any building more than three stories tall is required to be rated. This means the skeleton, or supporting framework, must be a one-hour fire-rated assembly. (An assembly is a tested and approved method or system of construction.)
If you have a facility that’s more than three stories, you only have two effective methods of construction: an all-concrete structural skeleton, which is typically poured-in-place concrete; or a class-A, structural-steel framework using a composite beam-type system (bar joists typically used in office-building-type construction don’t work well for this type of system).
This steel-beam and column system would then be coated with a spray-on fire-proofing material in the specified manner or possibly with intumescent paint, which is much more visually appealing but also more costly. Some developers are constructing a below-grade basement with three stories above grade to effectively create a four-story building without the cost of building four levels above grade.
In very general terms, it appears the added cost of a rated structure is around $10 per gross square foot of building area. So if you have a 100,000-square-foot, four-story building, this would add about $1 million to your construction costs. If you built the same facility with a basement and three stories above ground, assuming the soils aren’t too bad, the added cost would be about half.
Self-storage developers are getting very creative to accomplish their objectives. Some are producing projects with multiple levels below ground as well as building facilities up to seven stories high. Even with the added costs, this often makes economic sense and results in impressive projects in highly desirable locations.
Charles Plunkett is founder, owner and CEO of San Antonio-based Capco Steel Inc., which supplies steel and erects metal buildings, including self-storage and boat/RV storage. The company provides design for projects of all sizes as well as engineered drawings, unit-mix layouts, hallway systems, roll-up doors and more. For more information, call 210.493.9992; visit www.capcosteel.com.
