Re-roofing Solution For Roof Drainage Problems

The building that houses this Bank of America in Peachtree City, GA, had been experiencing roof drainage problems for a few years. While the building has an interesting and unusually shaped roof, the roof shape had nothing to do with the issues the building owner was having. Rather, the modified bitumen roof on the lowest part of the building wasn’t draining properly.

Identifying the drainage problems

There were two reasons for the roof drainage problems. First, the roof between the two wings of the building had not been sloped properly. So instead of water running off the ends of the building, it would pool up along the eaves — the water was not reaching the gutters.

Second, even though four drains had been installed properly for that section of roof, the saddles that divert the water to the drains had not been installed properly. So this added to the water accumulation and, as is typical in situations like these, leaks eventually developed. Stagnant water on a roof is never a good thing and it’s definitely a problem on a 14-year-old roof with asphalt that has begun to break down.

New roof slope for a fresh start

Our re-roofing strategy for the flat roof was to recover the existing modified bitumen roof. Leaving the modified membrane in place, we installed a layer of 1/2 inch ISO insulation over the top and then mechanically attached a 60 mil TPO membrane. 

To correct the roof slope on the center portion of the roof, our solution was to cut out a four-foot wide section of the roof along each of the two 70-foot eaves. Then we would use tapered insulation to achieve the proper angle toward the eaves. This would direct the water over the eaves and into the gutters, solving the roof drainage problems. There was no need to update the roof drains (they weren’t working anyway) so the best plan was to cap them. Adding a new oversized gutter on the side of the building with the bank drive-through would provide extra protection for bank customers.

Angled sections, edge detail, and why form should follow function

This roof has two distinct types of roofing working together to create one system. For the two roof sections that angle away from the building wings and toward the center of the building, we removed the old shingles and installed synthetic roofing felt over the plywood decking. Then we installed GAF Timberline High Definition Architectural Shingles.

It’s not uncommon for a property to have two or more types of roofs — we’ve worked on properties that have as many as five different types of roofing systems on one roof!

To complete the flat roof edge detail, we needed to wait for the rest of the exterior renovation to be completed. The client was working with an architect to install new wall panels on the sides of the building — once the panels were up, we’d know exactly how thick the roof edges would be so we could finish the detail. You can see us in the last stages of roof installation in the photo.

Coordination with the architect, client, and renovation contractor all went smoothly. The only related issue for the roofing portion of the project occurred before our re-roofing work began. When we were estimating the roofing budget, we noticed that a minor change the architect wanted to make to the structure of the building would negatively impact how the roofing system performed. We explained our concerns and the architect was able to revise the drawings, which ended up also saving the client thousands of dollars in construction fees as well.

Warranties

Two different roofing materials mean two different roof warranties — the shingle roof has a lifetime warranty and the TPO roof has a 20-year warranty.

While this isn’t one of the larger or more complicated re-roofing projects we often handle, it’s a good example of how working with an experienced roofing contractor can help you solve roof drainage problems to meet both your performance and budget needs. With a properly sloped, properly installed and properly draining roofing system — and regular maintenance with minor repairs, as needed —  you can protect your property successfully for the next 20 years and keep your tenants happy.