Self-Storage Roof Systems

September 1, 2004

6 Min Read
Self-Storage Roof Systems

Self-Storage Roof Systems

Top it off right

By Wayne Woolsey

The most basic components of a self-storage building can bethe most difficult to master. When it comes to selecting and installing yourroof system, there are a multitude of factors that will affect construction. Themost notable of these are roof type, pitch, penetrations, insulation anddrainage. This article provides an overview for the novice developer. While theroof installation may seem simple, critical details can mean the differencebetween a profitable business and a bed of insurance claims.

Roof Type

The first decision to be made is the type of roof panel touse. You can choose from screw-down panels or standing-seam roofing. Screw-downsystems are somewhat cheaper but will not serve for the long term. Insteadchoose a standing-seam system with a 24-gauge panels to accommodate 5-footspans. The panel finish should be Galvalume or a painted, not Galvanized.

Roof Pitch

In a self-storage application, you can choose a single- ordouble-pitch roof. Double-pitch roofing is preferred on a project that is 80 feetor wider, as shipping 80-foot roof sheets is not cost-effective in most cases.In this preferred installation, roof sheets are taken to the apex of thebuilding and the ends of the panels folded to create a positive stop end. Thejoint is then covered with a ridge cap.

Due to lot sizes and building locations in relation toproperty lines, you may not be able to pitch the roof in both directions. Inthis case, you can pitch the roof sheets in one direction, using a roof step toeliminate expansion issues. Adding a roof step that accommodates gutters anddownspouts will allow you to control and isolate water drainage from the roof.This design will help in the long-term maintenance of your standing-seam system.

A single-pitch roof involves caulking and screwing roof sheetstogether, which is just a leak waiting to happen. A standing-seam roof works ona floating-clip system. During expansion and contraction, which is likely tohappen in extreme changes in temperature, the sheets rub together, creatingelongated holes in their surfaces. The unfortunate thing about stitched roofsheets is once they start leaking, they are very difficult to repair. When you cannot use a single roof sheet due to excessivebuilding width, stick to a double-pitch roof with a ridge cap or add a roofstep.

Roof Penetrations

The goal of a standing-seam roof is to get all water thatlands on its semi-flat surface to move as quickly as possible, withoutobstruction, to the gutters and downspouts. This is why it is particularlyimportant to consider the placement and number of any roof penetrations.

The biggest penetration to the roof is the elevator shaft,which typically takes up an area of about 200 square feet. Unfortunately, itacts as a dam for water. After the roof type, the location of this huge waterstop is the next design question that must be answered. The most logical choice is at the highest point on the roofline. This will allow the least amount of water to travel behind the shaft.

Air-conditioning units, vent pipes, roof hatches and smokevents are other common roof penetrations. These should be kept to a minimum toavoid standing pools of water or opportunities for leaks. There are manymistakes that occur during installation of these fixtures, but the most commonis failure to divert water from the roof pans. This can be easily accomplishedby capping off the pans involved or installing diverter sheets. If you canprevent water from standing in the pans, you wont have to rely on caulkingand rivets to maintain a watertight seal.

Another common mistake is choosing a poor location for apenetration. Most of the time, there are options, but they are oftenoverlooked. Sometimes, penetrations are positioned to accommodate trades workingbelow the roof, creating convenience for those installing plumbing, ductwork orelectrical wiring. Ideally, penetrations should be kept as close as possible tothe high side of the roof. In the case of multiple installations, they should berun in a line parallel with the roof sheets to ensure the least obstruction towater flow.

Insulation Systems

Insulation is critical, as metal roofs will always accrue someamount of condensation, which can damage tenants goods. Insulation isdesigned to resist heat transfer and is rated by R-value, or heat resistance.The greater the R-value, the more effective the insulation is at slowing heatflow. Roof insulation comes as either a vapor barrier or part of a completeclimate-control system.

If you use a vapor barrier only, the minimum insulationrequired for the roof is R6, with a thickness of 1 inch to 2 inches. If yourfacility is climate-controlled, your insulation value will range from R13 toR19, from 3.5 inches to 6.25 inches. The important thing to remember aboutinsulating your roof system is there are proper roofs for different climates. Consult your supplier if you are uncertain which product isbest for your area.


You have installed and insulated your roof and sealed yourpenetrations. Now you need to consider the system by which water will drain fromthe roof: your gutters and downspouts. These are among the last items to beinstalled and common areas for problems. It is not unusual for architects to include insufficientgutters and downspouts in their designs to create the look they want for afacility. Yet they overlook the practical necessity of shedding water from theroof. While it is appropriate to keep aesthetics in mind, the No. 1 priority ofthe roof design should be to accommodate water runoff.

Water flow is critical. Therefore, roofs subject to largevolumes of water or those with longer roof sheets need gutters and downspoutsdesigned to carry the right amount of water per square foot of roof. As ageneral rule, you need one 4-by-4-inch downspout for every 1,200 square feet ofroof area. The roof must also have the correct pitch for the gutters anddownspouts to do their job. The minimum roof pitch for a standing-seam roof is0.25:12. For longer distances, you may want to increase your roof pitch to0.5:12 to get the water flowing off the roof.

Gutters must be installed with a minimum 1- to 3-inch gapbetween the inside face of the gutter and the outside face of the building. Thisis to protect the building in the event water overflows the gutters. It is alsoimperative to drip form the roof sheets. This is done by bending the lastinch of the roof pans down toward the gutters. Failing to do this is anothercommon mistake made by inexperienced installers. If the roof sheets are notdrip-formed, it gives water the opportunity to flow back underneath the roofpanel and into the facility.

Gutters for snow and ice need to be handled differently thanthose designed for normal rainfall. They will typically have added supports toaccommodate the weight and a low-profile front to allow snow to exit the roofwithout removing the gutter with it. In areas subject to excessive amounts ofsnow and ice, it may be a good idea to add heat strips to the gutter to avoidice-damming.

One final word of wisdom here: When you build a self-storagefacility, the first three words that come to mind are location, location,location. I agree: location of the sun to location of the roof tolocation of the gutters. When possible, position the roof so the sun alwaysshines on the gutters. This will help melt snow and ice and assist in drainage.

Following the above guidelines will help you avoid commonmistakes in the design and installation of your roof system: inadequate rooftype or pitch; insufficiently protected screw points; improper overlaps atflashings; excessive, misplaced or poorly installed roof penetrations; and lack of water drainage. Always follow the roofmanufacturers guidelines or work with a qualified, trained professional toensure the best possible installation.

Wayne Woolsey is sales manager for Kiwi II Construction Inc.,which offers in-house installation, design and engineering services nationwide.The company specializes in light-gauge building systems, conversions, climatecontrol and roofing systems for the selfstorage industry. For more information,call 877.465.4942; visit

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