flexiblefullpage
billboard
interstitial1
catfish1
Currently Reading

Roof renovation tips: Making the choice between overlayment and tear-off

Roof renovation tips: Making the choice between overlayment and tear-off

Roofing experts offer guidance on making the decision whether to tear off and replace the existing roof or to overlay the new roof right on top of the old one.


By C.C. Sullivan and Barbara Horwitz-Bennett | September 19, 2013

When embarking upon a roofing renovation project, one of the first decisions for the Building Team is whether to tear off and replace the existing roof or to overlay the new roof right on top of the old one.

“Typically, you’re reroofing because of leaks or damage to a roof,” says Shad Traylor, AIA, CDT, LEED AP BD+C, a LEED administrator with the design-build firm BRPH, Melbourne, Fla. “A tear-off allows you to inspect the condition of the roof substrate and is more favorable for roof warranties. If the load-bearing capacity of the roof substrate is in question, a tear-off also reduces the additional weight of a second roof.”

However, if  the roof has minimal water damage, he adds, reroofing with an overlayment strategy can be the quickest, least expensive, and easiest solution because it eliminates tear-off costs and reduces replacement time. “Overlayment also allows owners to maintain a weather barrier if sensitive equipment and products are installed or stored below the roof,” adds Traylor.

Analysis and testing may be needed to determine if the existing roof structure is adequate to support the added weight of an overlay. This can involve core cuts in strategic areas to analyze material conditions, as well as thermal scans and insulation tests. According to Anthony Vross, owner of Simon Roofing, Youngstown, Ohio, a rule of thumb is that if more than 30-40% of the existing roof is wet, then a tear-off is in order. The same is true in situations where the existing roof system is ponding water and it is not possible to add drains or taper insulation with the perimeters or penetrations at least eight inches higher than the primary roof surface.

In some cases, the decision on the type of reroof may be dictated by the applicable building codes. For example, where two roofing systems are already in place, most jurisdictions won’t allow the addition of a third layer of overlayment. Consequently, a tear-off or full replacement is the only allowable option.

Another instance favoring tear-off is when mechanical equipment upgrades require the roof decking to be rebuilt, in which case tear-off provides the best continuity, says Mark Yanowitz, LEED AP, Assoc. AIA, UCSL, with design-build firm Verdeco Designs, Andover, Mass. “Although there have been significant improvements in new insulation adhesives that make quality overlay roofing projects more viable, tearing off an existing older roof almost always assures a better installation and fewer problems in the future,” he adds. “This is largely because there are no unknowns with attachment issues as to how the previous roof was installed and the integrity of the overall system.”

A number of other factors need to be taken into account, including the building type, location, building usage, roof access, roof traffic, penetrations, decking, and slope.

Other techniques similar to overlayment, such as spray-applied foam products, may be viable alternatives. Another retrofit path for green building projects is the use of a “cool roof” coating, which is fluid-applied directly to the exposed roofing material. Assuming that the roof’s surface is relatively smooth, moisture is not a major concern, and decent drainage is in place, these novel, light-colored roof coatings can be a cost-effective option.

“The extra benefit is that the coating type conforms to all shapes and sizes and seamlessly seals all potential water entry points that typically leak, including flashings, termination bars, corners, pipes, and curbs and the like, which don’t always conform to the shapes of traditional roofing materials,” explains David J. Welte, President of the consulting and commercial building maintenance contractor GreenPROChicago, Lake Forest, Ill.

Vegetated or planted roof coverings may also lend themselves to part of a reroofing strategy as overlayments. For extensive, unoccupied green roofs, a common strategy is to cover existing roofs with plantings in individual trays. With some products, it’s even possible to remove the dividers between the trays, once they’ve grown, at which point they become a seamless blanket of vegetation, says Blake Jackson, LEED AP, Sustainability Practice Leader with Tsoi/Kobus & Associates (www.tka-architects.com), Cambridge, Mass.

“This type of system is most appropriate when you want to cover a surface quickly,” says Jackson. “This will contribute to earning LEED credits and help in terms of building performance and rainwater management.”

In virtually every situation, the sequencing, phasing, and coordination of the roofing work is critical to successful, watertight tear-off installations. Contractors should work from the low point to the top of the roof to prevent back-lap areas that buck water, says David Cook, AIA, Principal Architect in structural and architectural evaluation with CTLGroup (www.C-T-L.com), Skokie, Ill. In addition, sections should be worked in a strategic sequence so that workers don’t have to walk across finished work surfaces.

Protecting the substrate or deck is another key point, says Jason Hand, Vice President of roofing contractor Property Development Solutions (www.pdscompany.com), Lubbock, Texas. This also goes for the building’s contents at times when sections of the roof are fully removed.
“Weather must be tracked and precautions made to dry-in the structure at a moment’s notice,” says Hand. He, too, emphasizes the importance of staging roof work in portions. “The building assemblies should also be torn off in stages to limit exposed area in the event of unexpected precipitation,” says Hand.

Craig R. Garey, owner of roofing contractor WeatherSure Systems (www.weathersuresystems.com), Sheridan, Colo., advises going from the inside of the facility outward in identifying liabilities, risks, deck conditions, and design prior to beginning any renovation. Once a sound plan is in place, a disposal chute is the best way to transfer debris from the roof to the ground, unless the building height exceeds 120 feet.
Yanowitz is a proponent of reusing insulation and stone products to the greatest extent possible once the membrane has been removed and replaced. In cases where on-site reuse isn’t practical, trash hauling companies with off-site recycling facilities are a good option so that contractors don’t have to spend the time segregating products on site.

A roofing retrofit that involves changing a flat roof to a steep slope system can present its own set of difficulties. For starters, the structural engineer must ensure that the weight of the new roof structure meets the proper load bearings and dead-load requirements, says Simon Roofing’s Vross. The architect must verify that the building’s new look meets aesthetic and building code demands.

“Going to a steep slope from a flat roof will change the drainage design, so an engineer will need to be consulted to make sure the existing drainage system can handle the increased flow of the water entering the drains,” he explains. “Due to the amount of air space between the structure and the flat roof, the proper amount of insulation needs to be installed to meet the building code and prevent condensation.”

Related Stories

| Feb 17, 2014

Call for Entries: 17th annual Building Team Awards - Deadline Extended!

BD+C's Building Team Awards is the industry's only recognition program to honor projects that achieve excellence in both design/construction and collaboration of the AEC/O team. The deadline has been extended to March 14, 2014.

| Feb 14, 2014

ASHRAE, Green Grid team up on energy-efficiency guide for data centers

Vendor-neutral publication examines aspects of the popular power usage effectiveness (PUE) metric.

| Feb 14, 2014

Giant interactive pinwheel adds fun to museum exterior

The proposed design for the Santa Cruz Museum of Art and History features a 10-foot pinwheel that can be activated by passersby.

| Feb 14, 2014

First look: Kentucky's Rupp Arena to get re-clad as part of $310M makeover

Rupp Arena will get a 40-foot high glass façade and a new concourse, but will retain many of its iconic design elements.

| Feb 14, 2014

The Technology Report 2014: Top tech tools and trends for AEC professionals

In this special five-part report, Building Design+Construction explores how Building Teams throughout the world are utilizing advanced robotics, 3D printers, drones, data-driven design, and breakthroughs in building information modeling to gain efficiencies and create better buildings. 

| Feb 14, 2014

Crowdsourced Placemaking: How people will help shape architecture

The rise of mobile devices and social media, coupled with the use of advanced survey tools and interactive mapping apps, has created a powerful conduit through which Building Teams can capture real-time data on the public. For the first time, the masses can have a real say in how the built environment around them is formed—that is, if Building Teams are willing to listen.

| Feb 13, 2014

University officials sound off on net zero energy buildings

As part of its ongoing ZNE buildings research project, Sasaki Associates, in collaboration with Buro Happold, surveyed some 500 campus designers and representatives on the top challenges and opportunities for achieving net-zero energy performance on university and college campuses. 

| Feb 13, 2014

3 keys to designing freestanding emergency departments

Having physically disassociated from a central hospital, FEDs must overcome the particular challenges associated with a satellite location, namely a lack of awareness, appeal, and credibility. Gresham, Smith & Partners' Kristin Herman-Druc offers three keys to success. 

| Feb 13, 2014

Why you should start with a builder

They say the best way to eat an elephant is one bite at a time. Expanding your building or constructing a new structure for your business, church, or school isn’t all that different. Attacking it is best done in small, deliberate pieces. 

| Feb 13, 2014

Related Companies, LargaVista partner to develop mixed-use tower in SoHo

The site is located at the gateway to the booming SoHo retail market, where Class A office space is scarce yet highly in demand.

boombox1
boombox2
native1

More In Category

Urban Planning

Bridging the gap: How early architect involvement can revolutionize a city’s capital improvement plans

Capital Improvement Plans (CIPs) typically span three to five years and outline future city projects and their costs. While they set the stage, the design and construction of these projects often extend beyond the CIP window, leading to a disconnect between the initial budget and evolving project scope. This can result in financial shortfalls, forcing cities to cut back on critical project features.




halfpage1

Most Popular Content

  1. 2021 Giants 400 Report
  2. Top 150 Architecture Firms for 2019
  3. 13 projects that represent the future of affordable housing
  4. Sagrada Familia completion date pushed back due to coronavirus
  5. Top 160 Architecture Firms 2021