When the U.S. Air Force retrofitted a 7,800 square-foot building at Hurlburt Field AFB in Florida to meet a Category V hurricane with wind speeds of 157 mph, it proved to be a sound investment. Roof Hugger's sub-framing products played a prominent role in the metal-over-metal retrofit roof process.

Following the catastrophic damage from Hurricane Michael in October 2018 at nearby Tyndall Air Force Base and elsewhere on the Florida Panhandle, the project just 82 miles away suffered no damage, even with Michael’s documented peak wind speed of 155 MPH.

The existing building was a metal building constructed some years ago that needed a new metal roof. In lieu of removing the existing roof and replacing it and to minimize disruptions of ongoing activities within the building, the Base Facility Construction department elected a metal-over-metal retrofit - a system where a new metal roof is installed over new structural sub-framing that attaches directly to the existing roof’s support system, without removing the existing metal roof.

While doing this, the Base knew that it was possible to engineer the new retrofit system to be in accordance with current wind uplift design for the area.

In addition to hardening the building with the increase in wind uplift resistance, the Air Force included three inches of fiberglass insulation between the existing roof and the new metal roof.

Hardening of building roofs is very common on metal-over-metal retrofit roofs in the coastal States. Many older buildings were engineered for a 90 to 100 MPH wind speed and must be upgraded to minimum code requirements that are currently at 120 MPH inland and 130 MPH for coastal areas.

Some parts of Florida and Texas have requirements of 155 MPH or greater. U.S. Government facilities typically specify criteria that exceed locally adopted codes.

The work was performed by Royster Contracting LLC of Fort Walton Beach, Fla., a building construction firm on the Florida Panhandle since 1977 that has completed several metal-over-metal retrofit projects using Roof Hugger LLC sub-framing products.

Skip Royster, owner and founder of Royster Contracting, explained that Roof Hugger provided 2,700 lineal feet of their standard Model “C”, manufactured to fit over 12-inch on center “PBR” rib panel roofs. Central States Manufacturing of Lowell, Arkansas furnished their 24” wide Central Seam Plus trapezoidal standing seam roof in 24 gauge in Brite white for the new roof.

Since 1991, Roof Hugger has maintained a library of published and hand-drawn obsolete metal roof profiles that include their physical dimensions, rib spacing and other critical information. Having this allows in many cases to verify the existing roof profile that is being identified, ensuring the new Roof Huggers, manufactured to “nest” over the existing roof and its major ribs, fit correctly to provide a low-profile sub-purlin system

According to Roof Hugger, "There are a number of ways that existing metal roofs have been and still are being retrofitted. Many of these methods cannot be considered structurally correct sub-framing systems. They lack the ability to withstand wind uplift and therefore are subject to failure."

Over the past 26 years Roof Hugger sub-framing systems have been installed on over 85 million square feet of existing metal roofs and continue to be installed on approximately 6 million square feet annually. The systems have withstood hurricane force wind loads from Katrina, Ike, Michael and others without a single failure.

Advice For Retrofitting Metal Roofs

To help building owners nationwide, including federal and state governments, withstand severe weather, Roof Hugger offers the following advice for retrofitting metal roofs.

• Never install hat sections over the top of existing metal roof ribs. The hat section width will allow only one screw to be installed into the existing purlin. The other screw will be attached to the existing 26- to 29 gauge metal, which does not provide sufficient pull-out strength.

• Sitting on top of the existing ribs requires a long attachment screw and when exposed to thermal movement, they will “rock” back and forth causing fastener back out and ultimate failure.

• Don’t use wood purlins over existing metal roof ribs. Quantity of fasteners for the new metal roof will have to be increased due to the much reduced pull-out strength into wood, increasing installation labor and material costs. Pressure treated wood is corrosive when placed in contact with existing and new metal roofs.

• Stand-off clip systems over existing metal roof purlins require special attention. The manufacturer of the stand-off clips must have a system to provide required additional sub-framing in the edges and corners of the existing roof; this method is challenged to withstand the increased wind loads in these zones by reducing the purlin spacing to properly support the new panels.

• Sprayed-on Coatings: Most coatings are quick fixes and temporary solutions that fail to permanently fix the existing roof. Preparation of the existing roof is vital to the coating’s performance. They do not comply with new stringent Building Code wind speeds.

Preventive Maintenance To Protect Roofing Investment

Whether metal or single ply, Roof Hugger advises that the most important reason for establishing a program of regular roof maintenance is to protect the owner's investment. A properly executed maintenance program will add years to the life of the roof by detecting minor problems before they become major, as well as providing better protection for, and avoiding interruption of, the internal functions of the building.

According to the Roofing Contractors Association of British Columbia, a preventive maintenance program is simply a program of scheduled inspections and subsequent corrective action. The purpose is to maximize the life expectancy of the roofing system, thus providing maximum protection to building and contents and minimizing overall costs.

The basic elements of a preventive maintenance program for roofs are:

• Regular visual inspections to determine the current condition of the roof membrane and flashings.

• Immediate repair of any defect before it allows moisture to enter the roof system or building interior.

• Non-destructive moisture detection to determine if moisture has infiltrated into the insulation of the roof system.

• A vital part of the condition of the roof system is whether or not the insulation remains dry. A roof may appear to be in excellent condition from the surface, but may have areas of saturated insulation, which severely affect the thermal efficiency of the roof.

• Non-destructive moisture detection of roof systems has developed into a sophisticated technique that can provide accurate analysis of roof insulation condition. Two commonly used systems are nuclear meter and infrared thermography. Both systems require trained skilled operators, specific weather conditions, specific roof types, and professional analysis. Visual inspection by a trained person is the key to a successful maintenance program.

Inspection Guide

Roof Hugger recommends that roofs should be inspected at least twice a year — spring and fall — and also after any significant weather or construction event.

The inspection should be preceded by the preparation of a detailed roof plan on which all defects or notes can be marked. If the inspection indicates that more than minor work is required, an inspection checklist is necessary to ensure thoroughness. Call your professional roofing contractor to perform the required maintenance work.

Begin the inspection by looking at the underside of the deck, if accessible, and also at the outside of the building. Look for cracks, stains, rusting, watermarks, efflorescence, wet spots, spalled mortar etc. or other signs of excessive moisture or deterioration. The observations may give clues to not only roofing problems but also other conditions affecting the performance of the building envelope.

The final and most important part is inspecting the roof itself. The keys to a competent roof inspection are thoroughness and attention to detail — be prepared to get dirty.

What to do and not to do for roof maintenance:

• Do be aware that wise maintenance will prolong the life of any roof — even the best of them.

• Do perform inspections at least twice a year, preferably at the end of winter and right after summer, when roofs have passed through the periods of severest stress.

• Do conduct additional inspections immediately after unusual occurrences such as extremely heavy rains, high winds, hail, nearby fires, explosions, etc.

• Do check the building exterior for settlement or movement. Cracks in the wall are a warning of possible cracks in the roofing and flashing. Are overhangs, cornices, fascias and edging in good condition? Are gutters and downspouts satisfactory? Breaks in roof edge elements can cause leaks and also let wind get under the roofing membrane and cause blow-offs. Damaged or clogged gutters, roof drains, and downspouts can cause water back up on the roof.

•  Do be certain that equipment servicemen going on the roof are warned against penetrating or dropping tools on the roof. They should be accompanied by your trained maintenance man to ensure no damage to the roof assembly occurs.

• Do assure that your roof is kept clean and free from debris.

• Do recognize that exposure of roof felts (bare spots) on a gravel surfaced roof can lead to quick deterioration. This requires immediate attention by qualified personnel.

• Do be advised that flashings, gum pans, gravel stops and all other roof penetrations are the source of most leaks. Pay extreme and careful attention to these items.

• Don't allow unqualified personnel to maintain your roofs. Metal roof professionals are not the same as conventional roofing contractors; they have different skill sets and are not interchangeable.

• Don't allow traffic on your roof unless accompanied by your informed maintenance man.

• Don't allow equipment servicemen to penetrate your roof without being certain that qualified personnel flash the penetrations. If your roof is covered by a RoofStar Guarantee, RGC or the membrane manufacturer should be notified prior to cutting the roof or altering it in any manner.

• Don't permit products of unproven quality to be used on your roof.

• Don't be taken in by "cure-all" products, which can be applied by anyone.

• Don't take bids on projects without adequate, uniform specifications.

• Don't reroof over an existing roof unless a careful evaluation is made, and a qualified consultant or standards authority gives prior approval.

• Don't expect a guarantee to keep the water out of your buildings. Guarantees do not cover many of the problem areas of your roof.

• Don't think that the lowest price is always the best. Be certain you will not be faced with a number of change order requests for extras after a project is awarded.

• Don't deal with firms who cannot stand behind their work and will not be available when you need them. Remember that no product is better than the applicator.

Your building’s roof is one of your most valuable assets. Its installation, inspection, maintenance and repair are critical to protecting everything contained within walls of your facility. Protect it and it will do the same for you.