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The project began when a local homeowner needed help with a deteriorating flat roof. They were looking into putting the property on the market and realized the roof wasn’t in the best condition anymore. They knew it was old, years since it last had any repairs.
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The team arrived at the site and began inspections. We found that their roof had multiple roof layers which were not only outdated, but also trapped trap moisture. Then we found another problem. Overtime, debris and dirt built up, creating a lack of proper drainage. We built a plan for restoring the roof’s integrity.
Because the original roof was well past its prime—three complete layers, which exceeds Portland’s two-layer code limit—a total tear-off was mandatory. It’s more common than you would think for an aging roof like this, especially when moisture gets trapped and leads to rot.
For those of you quickly skimming the article, I don’t blame you. But here is a quick list of some of the challenges our team had to face to give you the big picture fast.
Excessive roof layers
Multiple roofs stacked on top of each other can harbor moisture and add unnecessary weight. In Portland, regulations allow a maximum of two layers, mainly to maintain structural integrity. Exceeding that limit can result in faster deterioration, code penalties, and higher repair bills down the road.
Rotted plywood
After stripping off the old layers, it became clear that sections of plywood were compromised. Here’s a before an after:
Rotted decking poses a significant safety risk and is more prone to leaks. To address this issue we had to not only replacing the damaged wood but also make sure everything beneath remained sound enough to support the new installation.
Standing/ponding water
Flat roofs often struggle with proper drainage, and this was no exception. Without adequate slope, rainwater can pool on the surface, weakening materials and speeding up the appearance of leaks. We were reminded of this as it rained quite a bit during the project.
Weather conditions
We all know rain in the Pacific Northwest can be weirdly unpredictable. Throughout the 2,400 sq ft. project, our crew had to keep a close eye on the forecast and protect exposed areas whenever the skies started turning gray and began to dump water.
A thorough assessment revealed the property’s roof was beyond patchwork fixes. Three layers had to go, and extensive rot needed immediate attention. To address both issues safely, the team started by mapping out each step: removal of old materials, replacement of compromised decking, and installation of a more resilient membrane.
For the new surface, a .60 mil IB roofing system was selected. This choice wasn’t made lightly—flat roofs demand materials that can stand up to heavy rain and occasional ponding, and IB was the solution for this case. On top of that, 1/4-inch fire-rated DensDeck board was chosen to add another layer of protection. Not only is it useful for rain, but it also improves flame resistance by reducing the spread of flame in case of a fire. Where plywood was beyond salvage, fresh boards were installed to create a stable foundation.
Once the plan was set, the crew tackled the tear-off. Stripping away all three roof layers—including one embedded with gravel—required care and persistence. Each section had to be examined for moisture damage, with any rotten decking replaced to prevent future structural issues. We wanted to create a sturdy platform that could support the new materials without risk of hidden deterioration.
Next came slope creation. On a flat roof, poor drainage is often the root cause of leaks, so the team took time to adjust the structure for steady runoff. Whether by installing tapered insulation or carefully leveling the surface, the goal was always the same: eliminate ponding and direct rainwater away from vulnerable spots.
With the substrate prepped, workers began placing the .60 mil IB membrane. Not only known for its durability in wet climates, this membrane resists tearing; useful when storms roll through. Boots, curbs, corners, drains, and scuppers were all fitted at critical points, making sure no seams or transitions would allow water infiltration.
Throughout the project, one of Pacific Northwest’s quirks added another layer of complexity to the project. Rain would sporadically pop up without warning, so we made sure to keep an eye on the forecast. Whenever it rained, the team quickly covered the roof to protect it and preserved their progress.
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In the end, we managed to wrap up the roof in ten days, even with the unpredictable conditions.
By the time the final membrane was in place, the roof met Portland’s code requirements, which got rid of any worries of inspections or potential fines. Removing rotten plywood and eliminating saturated layers meant the new roof had a much stronger foundation. No worries of costly leaks or future structural problems.
In practical terms, the improvement translated to better longevity and performance. The IB membrane’s strength and weather resistance minimized the likelihood of future leak events. For the homeowner, the enhanced curb appeal and peace of mind from the upgrade boosted the property’s value. Not a shabby perk.
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For those skimming this case study, all of this was accomplished within a tight schedule—ten days total. Thanks to the team’s planning and skilled execution, this major overhaul was kept on track and finished successfully.
When the work wrapped up, the homeowner told us they were grateful we were able fix their roof and install a new system. No more concerns about hidden water damage or anymore escalating repair costs. We also included yearly maintenance program was in place to catch any early signs of wear or tear.
The biggest lesson here is the value of thorough inspections. While you think you may not have any issues with your roof, in this case too many roof layers and areas of rotten decking went unnoticed until leaks become severe.
Another key point is material choice: cheap or outdated products can rapidly degrade in wet climates, leading to higher maintenance expenses later on. A solid membrane, like IB, stands up to heavy rain and ensures a more reliable surface over time. For us, this project was a success. We were able to help someone, improve a beautiful home, and raise our client’s quality of life.
If you live in the Portland, Vancouver think you spot a problem with your flat roof, give us a call at (971) 339-4299.
We start by showing up and giving your flat roof an thorough inspection to see how it’s been doing. (The most common problem we find is usually dust and debris that get trapped up there... as well as aging materials that leak) We are here to help if any issues are found.