A metal roof is a significant investment and the last thing you want to do is to make sure the installation process runs smoothly. Due to the expenses involved, many homeowners try to cut down on extra costs by installing their new roof over shingle or asphalt roof. While it may seem convenient, several potential problems can arise, compromising the roof’s structural integrity and durability. Metal Roof Over Shingles Problems is our topic today.
Here are some metal roof-over shingles problems you should be aware of:
The roof becomes susceptible to corrosion and rust
Many people invest in metal roofs because of the resistance they offer against corrosion; however, they can become susceptible to the same problem if installed over shingles. That’s because decay and rot can happen over time, regardless of how galvanized your metal roof is. The leading cause is water seepage. Oxygen, air pollutants, and moisture can combine to eat away the metal roof, which causes corrosion.
Unnoticed damage or fungus growth
Aside from the threat of corrosion, it’s almost impossible to notice any sign of damage under the roof or in the shingles. That’s because the metal roof will mask every damage from view.
There’s also the threat of fungus growth due to the shingles’ reduced airflow. That means trapped water or moisture underneath the roof will encourage these organisms to spread, especially along the roof’s edges. And that might damage the rafters and compromise the roof’s strength.
Added weight on the underlying structure
Another primary problem of installing a metal roof over shingles is that it places additional weight on the underlying structure. Unlike metal roofs, shingles are designed to be lightweight. And the combined weight of the new metal roof can exceed the required load capacity of the roof trusses. This can slowly lead to structural issues such as sagging. In some extreme cases, the extra weight may collapse the roof, especially if the metal roof is not adequately reinforced.
Shingles create an uneven surface
Shingles can create an uneven surface that can affect the appearance and performance of the metal roof. Metal panels may not lie flat when you install them directly over shingles. And this can create potential gaps or lead to buckling and bending, making it more susceptible to leakages, wind damage, and other issues. Proper preparation (including removing old shingles or using underlayment) is crucial to ensuring a level surface for installing your metal roof.
No chance of replacing rotten roof decking
One of the most common metal roof over shingles problems is that there needs to be a chance of replacing your damaged roof decking. During a replacement, the roof is removed to its decking, allowing your contractor to inspect it for signs of damage, rotting, or broken boards.
Installing your new roof over the existing shingles is only possible by tearing off the entire roofing system. This means you can’t be sure if your decking’s integrity can handle your new roof, and you won’t also know if it needs repairs.