Replacing a Modified Bitumen Roof with TPO

Replacing An Improperly Installed Modified Bitumen Roof — No More Wrinkles!

By the time we saw the roof on this church in Norcross, it was definitely time to re-roof. In fact, replacing this modified bitumen roof years earlier may have been a good idea. But since it had only been installed in 2003, the church understandably had wanted to get more life out of it — a modified bitumen roof should last much longer than a decade. If it’s installed properly, that is. 

What surprised us most about the roof’s condition

About 15 years ago a contractor had replaced the original ballasted EPDM roofing system with a new modified bitumen roofing system, leaving the original EPS insulation in place. For an unknown reason, the bitumen was never attached to the building. This allowed the bitumen sheets to move around and even blow around — the building’s maintenance crew had to lay the sheets back down after particularly windy days.

As a result, the first thing we noticed was the bitumen looked more like wrinkled bed sheets than a protective barrier. 

The second thing we noticed was the penetrations. You could see the membranes pulling away from them. There were problems with the flashing across the entire roofing system and the edge detail wasn’t installed correctly. There were also visible (and, as it turned out later, not visible) problems with the HVAC equipment pitch pans, plus the repairs that had been made over the years with tar and other materials weren’t to code or effective. While building maintenance personnel can be very skilled in many areas, even the best staff wouldn’t have been able to manage the leaks caused by an installation as faulty as this one. There were at least 50 leaks over the auditorium area alone, and many other leaks as well.

Why there had been no warranty on this modified bitumen roof

Low bids are very attractive. Often property owners aren’t aware of their re-roofing options or why one bid is so much lower than another. And some contractors are not always truthful about the type and magnitude of problems that can be created by cutting corners. The church had received an excellent price for a roof of this size but, unfortunately, it had to deal with constant leaks from the day it was installed. 

Not getting a warranty is another way to cut up-front costs. But in the end, it only makes things worse. While you initially save on inspections and other warranty-related costs, without the materials manufacturer inspecting the system, contractors can ignore the manufacturer’s specs and install the roof any way they please — including not actually attaching the roof membrane. They can also use inferior products and untrained installers.

How we proposed to solve this roof’s problems

Clearly, we felt this roof need to be replaced despite a competitor’s claim that it could be fixed. We proposed removing all of the bitumen and antiquated EPS and taking the system it down to its metal deck, which, fortunately, was in good shape. Starting over with a warrantied roof was the best investment for the church. The leaks would stop, they’d have an inspected, warranted system that would last a couple of decades, and they’d have our team of experts ready to help them with any issues that happened to come up moving forward. We’re glad our client agreed. Their days of unending whack-a-mole leak management would soon be over. 

Three of the surprises along the way

The property itself is not complicated. The building was formerly an office building — it’s a big rectangle and access to the roof is easy. The re-roofing project wasn’t complicated either. Our crews have a lot of experience replacing a modified bitumen roof section by section. But as with most re-roofing projects, we did experience a few unexpected events.

  • Day-one drama: corroded gas lines 

The first day on the job we had to spring into action. We found that improper flashing for the HVAC-unit pitch pans had caused significant corrosion of some of the gas and electrical lines that ran through those pans. It was a dangerous situation. We had to have the gas line cut off immediately. 

Luckily, nothing bad happened — other than the building having no AC for a while in the middle of summer. We had the mechanical contractor we brought in to repair the pipes on standby for the rest of the project, just in case. 

  • Jobsite restrictions: curious kids!

During one of the three weeks that we were replacing the roof, the church held a summer camp. The camp’s morning drop-off and afternoon pick-up took precedence over the re-roofing activities, of course, so we shut down operations during those times to not interfere with the processes. 

We’re used to accommodating unusual client scheduling issues and are glad to do it, but there was one camp-related workaround that was pretty unusual. Evidently, our hard hats were quite interesting to the kids and they distracted them from the camp activities. So our crew needed to stay away from the edges of the building while the kids were outside — we’re pretty sure that’s the first time we ever got that request. But we were happy to comply.

  • EPS adventures: “snow” in the middle of summer

Our crews saw first-hand what can happen to 30+-year-old EPS insulation when it’s removed — and it’s not pretty! Well, it’s a little pretty if you like snow.

EPS, or expanded polystyrene foam, is a white, styrofoam-like material within a rigid closed-cell insulation system (boards). It was used in the original EPDM roofing system and left in place for the modified bitumen system. Today, EPS is only used occasionally, such as to fill the metal roof grooves under a TPO membrane, because it melts at 250 degrees and is also flammable. Another thing EPS does is crumble, especially when it’s old. When it crumbles and flies around in the wind, it looks like snow.

Since there were 40,000 square feet of 4’ x 8’ EPS sheets mechanically attached to the deck, the process of unscrewing the sheets and preparing them for recycling caused some of the corners to break off and crumble into “snow.” And since we re-roofed in phases, removing the EPS as we progressed, we dealt with EPS “snow” cleanup throughout this re-roofing project. Our crews were out there sweeping and bagging several times so the job site stayed presentable.

Recycling and reusing

While we were not able to recycle the modified bitumen roofing material, we were pleased to be able to recycle all of the EPS. Sentry is committed to sustainable roof design and we recycle, repurpose and reuse materials whenever possible. We bundled up the EPS boards for a recycling company.

The next time the church re-roofs, however, it’s very likely it will be able to reuse much, if not all, of the 3.5 inches of new ISO we installed to meet thermal code. The new insulation will not only significantly lower their net replacement bill but also lower their energy bills each month. They should be able to recycle the TPO membrane next time around as well. 

A 20-year warranty and kudos from the inspector

This project was not without its hiccups but Northlands Church now has a brand new roofing system with a mechanically attached Firestone 60mil TPO membrane and a 20-year warranty. To top it off, the Firestone inspector said it was one of the best re-roofing jobs he’d seen. 

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