COLUMNS

Retrofit Metal Roofing And New Construction?

By Mark James, formerly of MBCI NuRoof Systems

We all know that the word “Retrofit” is used to describe several attributes that are around us everyday. It implies many things in many industries. In general however, it refers to the addition of new technology or features to older systems. More precisely, in manufacturing Retrofit describes the measures taken to allow new or updated parts to be fitted to old or outdated machinery, assemblies and processes.

In the Metal Construction industry, Retrofit is a term that is synonymous with alterations and improvements to an existing flat roof building. It is a concept of constructing a sloped framing system with metal roofing over an existing flat roof building. This concept has been referred to as Retrofit Re-roofing, Slope Framing, Slope Build-up and Overbuild. Regardless what term is used or whether we adopted a wrong word or not, the end result is a new roof that has the ability to discharge rainwater to the outer limits of the building. In addition to this concept and to be fair about things, we have to mention “Metal-over-Metal” systems. These typically employ a structural sub-purlin that is attached to the existing roof and/or structural system. At that point, a new metal roof is installed to provide the building owner long-term performance and reliability.

However, this column is about “New Construction”, so let’s continue on on that basis. These alterations and improvements can be for different purposes. While one building owner may only wish to create positive roof drainage, another may want to utilize the roof as a design element in the overall beautification of his/her building. Then, others may have the need to utilize Retrofit framing to eliminate issues caused by problematic geometry within the perimeter of the existing roof. For a number of applications associated with existing buildings, the concept can be employed as a genuine solution for correcting conditions that have proven to cause leaky roof environments.

The framing system and its components are what make the concept so versatile and purposeful while the metal roof cladding that is installed over the framing provides the building owner long-term performance and related life-cycle savings. Of course let’s be fair again and mention that if you have a particular application that requires the Retrofit framing without the metal roof, then you might be in luck. These framing systems can be engineered to support virtually any roofing assembly as well as design loads. This is true whether the finished roof will be a standing seam metal roof, clay tile or composition shingles over plywood.

Photo 1  (click photos to enlarge)

Photo 2

Photo 3

Photo 4

Photo 5

Photo 6

Now let’s see what else you can do with the Retrofit concept. Have you ever thought about using Retrofit to create the roof geometry on a new building? These framing systems can adapt to pretty much any type of support structure whether they be steel, wood or concrete. For many years now, building owners, design professionals and contractors have discovered that using these light-gauge fully-engineered framing systems to erect a sloped roof on a new building can be very competitive to other alternatives.

Many types of building occupancies have employed the Retrofit concept to establish their new roof geometry. In kind, owners and design professionals have been afforded the economy and associated financial savings from these systems.

The US Navy has used it on dormitories, High-rise developers have used it for curved barrel roofs on office buildings, Architects have employed it for the roof system as well as roof screens on major condominium projects (photos 1 and 2).

Design-Build contractors have even used it to build a Cloud in Las Vegas. Probably the one that uses it most for new construction is the Hotel industry (photos 3, 4 and 5) where they construct a multi-story poured-in-place concrete structure. In many cases hotels have used the concept for roof screens only that create a false roof when viewed from the ground level. But then, they are used to frame a fully enclosed roof system atop a new concrete attic deck. When this is done, it is common for the design professional to restrict the Retrofit System manufacturer and Engineer to a maximum point load at each base member attachment location. What this does is to prevent the attic floor deck from being overloaded by controlling the spacing of vertical members that support the new roof purlins.

More simply, an engineering calculation is performed using the specified design loads to determine the maximum spacing of the retrofit columns/posts and possibly the roof purlin spacing as well. One hotel ownership company that has used the concept for multiple properties is Williams Investment Co. of Adel, GA. They currently have Holiday Inns®, Comfort Suites® and Comfort Inns® in service or under construction. Each are approximately 24,000 square feet of roof area using MBCI’s 16” LokSeam standing seam in Signature 300 Copper Metallic. The architect for these facilities was David L. Wallace & Associates of Dunedin, Fl and the general contractor is Pinnacle Prime Contractors of Valdosta, GA. The certified installer for the MBCI roof system is Bryant’s Millrights and Construction of Norman Park, GA. To capitalize on the energy efficiency possibilities of these systems, a reflective bubble radiant barrier was installed beneath the new roof panels and of course the entire attic space was ventilated using MBCI’s vented ridge assembly.

Another building use that has utilized the concept frequently is correctional facilities for local, State and Federal facilities. In these cases, creating and maintaining a secured enviroment is hallmark to the design and functionality of the facility. Retrofit provides an excellent solution to providing a protected area above the secured confines. Beneath the new metal roof, mechanical and electrical systems can easily be installed atop the ceilings. In many cases, these ceilings are constructed with precast concrete planks. The planks are set in place and the retrofit framing erection commences. In areas that are not secured zones, conventional construction may be used or retrofit is used over open web bar joist and metal deck (photo 6).

So why is this Retrofit framing concept used in new construction? Consider the following next time you are developing a design for a new building:

• Light-gauge zees, cees and other shapes have span capabilities that are greater that the typical hat section members used in pre-engineered truss applications thus reducing the amount of steel framing needed.

• Because of the greater span capabilities, mechanical and electrical systems can be installed beneath the new roof with maintenance access provided through various methods such as hinged vertical surface louvers, roof scuttles, etc.

• Retrofit framing uses commodity type components that are readily available from a wealth of sources virtually anywhere and anytime.

• Retrofit framing can be engineered to receive metal or plywood decking to accept conventional sloped roofing systems (composition shingles, tile, etc.)

• Retrofit framing systems erect as quickly as wood and light-gauge systems.

• In most cases, the Installer of the metal roof system will erect the Retrofit framing system.

• For curved applications, a structural metal roof can be used thus eliminating the need for solid decking. Note that extreme care must be taken during installation of this type of roof geometry to minimize oil canning.

• For new construction projects that also include an existing building that is being renovated, Retrofit can be an answer for the design professional to tie the old into the new using the roofs as a design element.

• Insulation is installed at the attic floor level and the cavity between the deck and new roof is ventilated to satisfy condensation concerns as well as providing energy efficiency.

• In this day and age of high oil prices, metal roof systems have become very competitive with conventional petroleum based roof systems.

Mark James is the former General Manager of MBCI NuRoof Systems. He has been an active contributor to the growth of the retrofit concept in the metal construction marketplace since 1986. Mark has been instrumental in the successful preparation and completion of over 20 million square feet of retrofit projects. His 35-plus years of construction industry experience includes the design, sales, fabrication and construction of conventional and pre-engineered buildings and architectural metal roof systems. He is a recognized and accomplished technical seminar speaker/presenter for building owners, contractors and design professionals seeking knowledge needed to properly retrofit existing buildings.

To view other columns by Mark James or other columnists, click here.