Last week on METALCONLive!, the Metal Construction Association presented leading authority on metal roofing recover systems, Charlie Smith with McElroy Metal, who gave a detailed presentation on the benefits of using metal to recover an existing sloped roof. You can stream the presentation on-demand by clicking on the above image. Some key takeaways from the presentation include the growing advantages of using metal for roof recover work, the future of using a “T” shape panel and if doing a retrofit, and knowing your clip offset before starting a project.
Charlie opened the presentation with the simple, yet important, question, “Why metal?” He answered his own question by saying, “Simple, it has the longest life expectancy of approximately 40-60 years.”
“The number one reason why a metal roof fails is poor installation,” stated Charlie. Training, especially with the installation of end laps, is key to the success of a metal roof. He explained end laps are the single most preventable source of a leak along with exposed fasteners.
Currently, the most common recover system in the marketplace is the trapezoidal structural standing seam panel. Charlie explained its benefits — “It is great for lower slope applications, good use for recovers, good wind uplift and it is watertight.” He went on to say the chief disadvantage is once they are installed, they are difficult to alter after the fact. Given this disadvantage, Charlie said, “the future for recover & new construction is the “T” shape panel because it gives you the ability to make simple and easy repairs which you don’t get with double folded seams.” Charlie recommends using symmetrical seams because of the advantages of its easy repair.
Another advantage of symmetrical seams is most have a watertight seam design. Charlie explained, “The design uses continuous clips which provide the highest wind uplift capacity (especially good for recover work), they are easy to repair or modify, eliminate panel end laps, and can pull panels out in 5 minutes with un-seamer.”
Remove and Replace or Recover?
Some questions to ask yourself to decide whether to remove and replace a roof or recover it are:
- Are you going to disturb a building occupant if you remove and replace?
- How much more weight can the building structure support? If it can’t take anymore weight, recover may not be possible.
- Can the connection to the existing roof meet current wind uplift and structure, codes? (for example, if new roof meets 3 lbs per sq foot weight, then can put a new roof on).
- Does the building need to be brought up to current energy codes?
Charlie advises to “Re-think a low slope curve roof as it has a tendency to pool water too much.” He suggests using transverse panels on the sides of curbs to prevent water pooling. Transverse panels are especially good for recover work and helpful with roofs with skylights (showed an example of a roof he recovered for a Chicago-based company).
According to Charlie, the number one way to cover a metal roof with another metal roof is with notched purlin. In most cases it will add strength to the underlying purlin and increases load capacity.
Before starting a retrofit project, Charlie advises, “know your clip offset!” He explained, “Knowing this will dictate the method for your retrofit. To recover, you have to know what method you’ll do.” Currently, the most common method is to use a model T-roof hugger.
Charlie reviewed the different types of retrofits including the example of placing a metal roof over a shingle roof. Having proper ventilation is key in doing a shingle roof recover. He advised using continuous clips as a way to attach to the shingles and then lay the metal roof over. By creating air flow between the shingles and the metal roof will decrease the heat transfer into the home.
Thank you to the Metal Construction Association and Charlie Smith for this excellent presentation.