As the nation’s building stock ages and a tight economy limits new construction, there is great potential in retrofit projects. Particularly with government, institutional and education buildings, where long-term operational quality and durability are of vital importance, owners and communities seek solutions to get the most possible use out of their structures.
Metal roof and wall systems are well-suited to retrofit projects and can add many years to the life of an existing building. That said, metal retrofits aren’t necessarily the ideal choice for every job. If a project has a short window for its return on investment, for example, the owner often will incline toward a more inexpensive roof system in spite of the fact that the roof will have to be replaced in 10 or 15 years. For those looking at a 20-, 30- or 50-year investment, however, a long-lasting metal retrofit makes a great deal of sense.
“Our retrofit customer is someone who is looking at the long-term benefits of the project,” says Mark Lawson, vice president of sales for Bossier City, La.-based McElroy Metal Inc. “There is a higher cost going in, but over the long term, metal is a very beneficial product. It has tremendous energy efficiency, it’s recyclable and the owner gets an upgrade in curb appeal. We’ve had architects tell us that appearance is one of the reasons they’ll choose metal for roof retrofits on schools. Schools are looking for energy savings, but when you put a steep metal roof on the building, the aesthetics are beautiful. People in the community feel their tax money is being spent on something that looks great when they take their kids to school.”
One of the reasons school and institutional buildings are so well-suited to metal roof retrofits is that they often have concrete, brick or concrete masonry unit (CMU) wall systems that are designed to last 60 or 70 years. Rather than constantly replacing a less durable roof system several times within that lifespan, it often makes sense to invest in a single retrofit installation that will carry through the performance life of the building. “When the wall systems are looking pretty but the roof is beginning to fail and the building has leaks all over the place, you really have to examine your choices,” Lawson explains. “If you have to put on a new roof, you have to decide whether to get the financial backing for a steep slope metal roof that gives all the beauty and performance you need or to just put a less attractive flat roof back down.”
Up On the Roof
The metal construction industry has been taking on retrofits for some time, and has made the process increasingly efficient. “In the early 1990s, most of the retrofits we were involved with were made out of light-gauge trusses assembled out of galvanized members. You build a form on the ground and it lay it out, build a truss in place and set it up on the roof,” recalls C. Wayne Fulmer, president of Lexington, S.C.-based I&E Specialties Inc., a metal roofing contractor. “In the past decade, most of the retrofits we’ve been involved with have been post-purlin retrofits. Now we build in place on the roof instead of pre-assembling the system in the parking lot and setting it up onto the building. This allows greater versatility.”
“What you’re doing on a retrofit is building 5- and 10-foot grids,” Lawson explains. “A local engineer will review the structural stability of the existing building and provide as-built drawings. We then select one of four designs, which are used to start the structure. A base shoe or base zee angle is fastened into the existing roof. A high point and low point are picked on a run from eave to ridge and eave to rake. That is set using strings as a method and the rest of it is basically stick built. Generally, 20-foot pieces of 16-, 14- or 12-gauge red iron structural zee or cee are used as sub-structural elements. We use cees for columns and zees for purlins. Typically, a clip will be used as a connection point from the column to the purlin or sometimes four self-drillers are put right into the existing column. It’s something like building the skeleton of a mini storage facility.”
The existing roof often is able to stay on underneath the retrofit metal roof system unless weight is an issue, in which case it must be removed. For example, if the old roof is saturated with water or near failure, it may have to be taken off. If it is a ballasted system with gravel, the rock has to be vacuumed off. “As a general rule, what you vacuum off in gravel is more weight than you’ll add with the retrofit,” Fulmer says. “Usually you’re OK on live loads and dead loads. Most buildings that have a flat roof are very structurally designed in the first place because of the amount of weight up there, so it usually isn’t a problem.”
Water is another consideration. “Probably the most difficult job is to put a retrofit roof on a foam roof because that foam roof is nothing but a great big sponge,” Fulmer says. “We had a building we were retrofitting and, even though it hadn’t rained in two weeks, when we started drilling through the foam to put our base clips down, water started dumping out of the foam and drained into the building through the screws. Water is the number one enemy when doing a retrofit roof. You have to prevent water from getting into the building.”
According to Fulmer, a TPO roof offers the best scenario for a metal roof retrofit. “TPO is really easy, mainly for the fact you don’t have to worry about waterproofing it,” he explains. “As you’re framing it, it’s easier to keep the building dry. You don’t have to vacuum the rock off it, it’s a more level surface to deal with and it tends to drain better when it rains. And usually with a TPO-style roof, you don’t have to worry about there being coal tar pitch up there. If you’re dealing with a coal tar pitch roof, it’ll eat you alive.”
One of the great advantages to metal roof retrofits is that the building often can remain in operation while the work is done. “There is no interruption,” Lawson asserts. “Most schools like to do these projects when the kids aren’t there, so you’ll see a tremendous buildup in May and June, but in most commercial, industrial or institutional buildings, buildings stay open. As long as there is appropriate safety for entrance and exits, there shouldn’t be any problems.”
“That is part of the beauty of retrofit,” Fulmer echoes. “We’ve done a number of schools and nobody moves out. The only problem you have is noise. Sometimes you have to work around the owner to minimize noise.”
While the installation may only take a few weeks, the benefits of retrofit metal roof will last decades. Along with being made up of highly recycled and recyclable materials, a retrofit roof also adds a good deal of energy efficiency to a building and will save on heating and cooling loads in the long run. “In many instances, owners are putting in additional insulation and using the added attic space to provide better R-values for the entire building,” Lawson says. “You also get reflectivity from the metal panels, which really helps.”