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Retro - Fitting Over Existing Roofs



   Author: D. V. "Red MC-1" McConnohie
Location: Tampa, FL


D. V. “Red MC-1” McConnohie, inventor of the Roof Hugger Sub-Purlin, Director & Partner, Roof Hugger, Inc. With over 40 years of design/build contracting of metal structures in the U.S. and overseas projects.

Dale Nelson, President, Roof Hugger, Inc., graduate, Northern IL University in Business & Finance. 30 years design/build contracting of metal structures in U.S. and overseas.

Charles “Chuck” Howard, P.E., Ohio State College of Engineering. 30 years design & construction of conversions of conventional flat roofs into sloped metal roofs.

Mankind has always sought to have a roof over his head. The maturation of roof technology has run the gamut from caves through palm fronds, thatched, sod, shingle, tile, built up tar and gravel and now metal alloys.

All, except the deep cave, have one thing in common: the problem of wear and tear by the elements and eventual failure. THERE -- IN LIES OUR OPPORTUNITIES! Where is our vital and essential roofing industry today in terms of employing the knowledge and skills our trades possess in these large new markets?

The past 50 years has seen enormous progress in both materials and technique which have led to ever growing roof life, cost –to-benefit-ration.

This is particularly true of the metal roof industry which has exploded with the advent of the “pre-engineered metal structures” designs which presented a revolutionary change from the conventional “stick built” buildings and now dominates the one and two story market in the commercial – industrial – institutional and recreational construction field with over 65 percent of the contracts to build.

Why? The goal of architects, engineers and specifiers over the centuries was to identify the lightest weight material combined with “life cycle” performance and aesthetic appeal for the final roof cover, especially in the non-residential area where large clear span areas were essential.

The lighter weight-to-strength ratio allowed design of lighter support structure members, easier, faster erection, and, in some, a more economically feasible shelter to protect large areas from the vagaries and destructive forces of nature.

World War II spurred massive demands for fast, low cost shelter which was answered by the steel industry with the Quonset hut. In the 1960’s a number of technological advances all came together with the advent of the computer that facilitated design of the tapered, indeterminate frames of today capable of clear spans of considerable lengths. Further strides in metallurgy, protective coatings formulas, weather head self drilling fasteners, resins, polymers and plastics have brought us to the modern steel structure. Not to be left out of this burgeoning new market, machinery suppliers quickly came up with sophisticated automatic welders, roll formers, slitters and folding machines that vastly increased production and quality.

Together, the combination created an entire new industry within the construction field as exemplified by the most recent statistics published by Metal Construction News magazine “Product File and Directory” Survey and MBMA (Metal Building Manufacturer’s Association) Estimate, January, 2003 Edition, Page 8, “Metal Roofing Market for 2003”, 1.75 billion sq. ft. of that amount, 525 million sq. ft. is for METAL ROOF REPLACEMENT. THAT IS WHERE WE ARE WELCOMED IN THE DOOR!

525 million sq. ft. of replacement metal roof translates into field contract value of labor and materials of over two billion dollars annually – and growing. That is hardly an insignificant amount awaiting the expertise of our trades.

The old practice of tearing off the old roof to replace it carried with it many liabilities and added costs. The building was opened to sudden weather changes, falling debris that made a mess on everything below and business was interrupted for a prolonged time – again, dependent on weather changes.

The demolitioned materials had to be hauled away, much of which is now labeled “unfit for standard land fill” and must be treated as hazardous waste in many EPA rulings so that more cost is added.

To further complicate matters, the more recently constructed buildings of the past 30 years for manufacturing and storage facilities have gone up in eave height to 28 to 34 ft. to accommodate modern “hi-lift” storage racks to make profitable use of the cheaper cubic foot of space in lieu of floor space.

The resulting mass of racked inventory is also often of high cost, fragile items susceptible to severe damage even by excessive dust. To shut down a fast paced business of such a nature is simply not acceptable to the owner/tenant who therefore diligently seeks an alternative.

To his rescue, here come the experts in metal re-roofing over the existing roof. Not exactly “the Marines have landed and the situation is well in hand”, “Dirty Harry”, Clint or John Wayne, but to that owner, we are just as welcome we can solve his problem with no interruption of business, no opening his building roof and in most cases he will probably hardly know we are there.

Whether he has a flat roof with B U Tar and Ballast or a ribbed metal roof, today’s highly specialized systems will meet his every need. Many firms exist as single source engineering; materials and labor for converting those flat roofs into sloped metal roofs with positive drainage adjustable stanchions anchor the light gauge, light weight framing and roofing to create “attic space”.

One of the early experts in the challenging conversion of flat to sloped roofs, is, Charles “Chuck” Howard, P.E. whose expertise in design and construction of such has covered several decades. Conversions require structural analysis of existing structure load capacity, support layout and aesthetic appearance.

The results are worth the effort as the owner now has a long life roof, lowest maintenance and “fresh new look”. “Chuck” can be found at: chuck@metalroofconsultants.net or by phone at (919) 349-2118.

For existing sloped metal roofs, a re-roof became a simple matter with the introduction of the unique “Roof Hugger” Sub-Purlin “Z”, punched to fit over existing ribs with the bottom flange “nesting” into the valleys for secure structural connection into existing support purlins and achieving absolute minimal roof height change.

Introduced nationally in 1994, the formed Sub-Purlin has created a large and profitable new industry for a host of metal building contractors and erectors because of its simplicity and rapid re-roof completion time.

What was a job to be avoided due to the liability and costs involved in “tear off and replace” is now a source of revenue eagerly sought fitting neatly over any rib style from old 2.67 inch corr. through today’s sophisticated array of standing seam designs and web heights to suit insulation or mechanical requirements, the Sub-Purlin became an instant favorite and are now in wide distribution through metal building and component manufacturer’s nationally.

Availability of the fully engineered and certified Sub-Purlins have largely eliminated several less desirable “Make Do’s” in the field in attempts to comply with owners pleas to not tear of the old roof and shut down his business.

These “Make Do’s” included using wood 2 x 4’s “Sleepers” in the valley, another 2 x 4 across and impaling the new roof to the wood frame (some used treated lumber which corroded the new sheets when the sun baked out the highly corrosive preservative chemical) while the untreated often “warped” creating unintended problems.

That art was further refined by using light gauge “hat” channels lying on top of the already degraded ribs of existing old roof. Which produced other “unintended consequences” such as over torquing of the single long fastener into the purlin and “crippling” the rib so that little to no support was provided. Only one fastener could be used to fasten to the purlin because the “hat” rails were wider than the purlin lip. Wind failures occurred from that trial.

The next step in “Make Do’s” was to use a “hat” channel “sleeper” up the valley, fastened by two fasteners into the underlying purlin, then another “hat” longitudinally, fastened to the “sleeper hat”. A structural four fastener connection but again, “unintended consequences” showed up when using the old stand by “R” panel for the new roof, through fastened into a rigid connection, thermal movement of the roof panel “backed out” the fasteners and elongated the holes – result? Leaks!

The notch punched sub-purlins, replicating the original structure design of “Z” purlins has solved those many problems as did adjustable stanchions solve flat roof conversions.

There are many other engineered and approved systems on the market by major manufacuturer’s to address the need for “non invasive”, retro-fit procedures and a great deal of progress has been achieved.

Looking at a 2 billion plus dollar annual market today, one must factor in the reality that nearly 5 times as many metal roofed structures have been built in the past 25 years as were built in the preceding 25 years. The future of solid growth in this specialized field is assured.

The time to position oneself as a knowledgeable proponent of metal retro-fit, is now. Look for the systems that best position you in the marketplace, learn all about them and proceed to secure yourself a “front row seat” in this lucrative field.

Every roof out there is aging by the day. Every year comes a new “crop” of roofs in dire need of your services. 500 million sq. ft. a year will soon be 750 million with no end in sight. If a roof leaks bad enough – IT WILL BE REPLACED!

Architects, engineers, specifiers and roof consultants are essential ingredients to guide the owners, contractors and erectors to the correct decisions in roof replacements!

Recent certified engineering load tests undertaken by Roof Hugger, Inc. have confirmed that the “Sub-Purlin” attachment system for the new “Roof-Over” panels adds live and dead load capacity to the existing support system in both strength and stiffness by some 20% of rated capacity, thus putting to rest questions of excessive imposed dead load of some 2 lbs. PSF of the “double roof condition”.


Comments: Retro - Fitting Over Existing Roofs

A very informative article. All that is needed now are some directions as to where your readers can obtain plans for adding a lift over an existing roof. Good reading Les
By Les
Do you know of a company that does the "metal roof over a flat roof" in the Tampa/Brandon area? Do you know the approximate cost per 100 sq ft? I have searched on Google for hours looking for options to re-do our flat roof, and this looks promising. I also saw a "wedge" build up system on HGTV but cannot find any info on that either. Any suggestions or other options would be appreciated thanks
By Myrna
cool site.
By Pat Williams
Cool site.
By Rob Miller
Thanks for sharing this informative article . Gulf Coast Supply is able to provide roofing materials for any commercial, residential, architectural or agricultural project that you may have.
By annmark
Post a comment > -


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