If your San Antonio home has an older asphalt shingle roof that you’re looking to replace with metal roofing, you may wonder: can I install a metal roof right over the existing shingles? This might seem like a convenient and money-saving option, but you need to consider the potential drawbacks and long-term consequences. While it is possible to install metal roofing over shingles, most roofing contractors don’t recommend doing so. In this blog, we’ll delve into why installing a metal roof over shingles might not be the best idea.
A raised roof profile can create issues with windows, water drainage, and aesthetics. If not properly addressed, water runoff from the raised roof profile may be directed towards windows, increasing the risk of water intrusion and leaks. Water runoff may also be directed towards the siding and exterior walls, increasing the risk of water moisture damage, and mold growth. Proper gutter and downspout installation, as well as strategic grading and landscaping, may be necessary to mitigate these issues. Changes in the roof profile can also have aesthetic implications. The altered proportions and clearance may affect the visual balance and symmetry of the building’s facade, impacting its overall appearance and curb appeal.
One of the primary concerns when installing a standing seam metal roof over existing shingles is the added weight. While a single layer of shingles might not pose a structural problem, adding the weight of metal roofing on top could exceed the load-bearing capacity of the roof framing and stress the roof deck and home. This excess weight can lead to sagging and structural damage that will appear over time which can lead to a greater roof repair or roof replacement expense sooner than expected.
Asphalt shingles are installed in an overlapping manner which makes your roof uneven. Any imperfections or height differences in the shingles will transfer through to the metal roof. When roofing contractors install a metal roof over shingles they will use furring strips to create a new frame for the metal panels. The problem is that the furring strips are installed upon an uneven surface and this can allow moisture to accumulate between the two roofs. Moisture trapped between the layers of roofing materials can lead to mold, mildew, and rot. Over time, this moisture buildup can compromise the integrity of the roof decking and insulation, resulting in costly repairs and potentially hazardous living conditions.
A roof deck is a layer of wooden boards that form the base for your roof system. Usually when replacing a roof, the roofing contractors will remove the old roof all the way down to the decking to see if it’s in good condition. They’ll look for broken or rotting boards and replace them before laying down a new waterproof membrane and then the metal roof. However, if you lay a metal roof over shingles, you’ll never know if the deck is in good condition or if it can even handle the weight of an additional roof. This can shorten the lifespan of your new metal roof and cost you more money in the future for repairs or early replacement.
By layering a metal roof over shingles, you introduce a layer of complexity that can make identifying and addressing leaks more difficult. In the event of a leak occurring in the roof system, pinpointing its source can become an arduous search. Is the leak stemming from the original shingle roof, or has it breached the metal roof’s barrier? This ambiguity not only complicates the detection process but also lessens the effectiveness of future repairs. Without clarity on the source of the leak, efforts to fix the issue may prove futile.
Standing seam metal roofing is known for its energy-efficient properties. Metal roofs help to reduce heating and cooling costs by reflecting solar heat away from the home. However, when installed over shingles, this efficiency can be compromised. The trapped air between the metal roof and shingles can act as an insulator, reducing the effectiveness of the metal roofing’s reflective properties and increasing energy consumption due to excessive trapped heat.
Installing a metal roof on top of a shingle roof may not be allowed in your area and permit requirements often dictate tear-off of all existing roofing. It’s important to consult local building authorities to understand the specific requirements and limitations governing roofing installations in your area.
- Building Codes and Regulations – Building codes and regulations dictate the permissible roofing practices in a given area. Some jurisdictions may allow metal roofs to be installed over shingle roofs under certain conditions, while others may prohibit this practice altogether.
- Manufacturer Guidelines – Metal roofing manufacturers usually provide installation guidelines and recommendations for their products. These guidelines may include specifications regarding substrate preparation, underlayment requirements, and installation techniques. Before installing a metal roof over shingle roofs, it’s essential to review and adhere to the manufacturer’s instructions to ensure you don’t void the warranty.
While the tear-off process takes more time and work, you’ll end up with a safer, longer-lasting metal roofing system. Instead of overlaying shingles with a metal roof, which you may think is less expensive and easier, the recommended approach for a proper install is to:
- Completely remove and dispose of existing shingles and felt.
- Make any needed roof deck repairs.
- Install new waterproof membrane.
- Install metal roof per manufacturer specifications.
While the idea of installing a metal roof over shingles may be tempting for its perceived convenience and cost savings, it’s important to weigh the potential risks and drawbacks. From structural concerns and voided warranties to aesthetic issues and decreased energy efficiency, the downsides of this approach can outweigh any initial benefits.
As with any new roofing project, be sure to work with a qualified metal roofing company like Jimmy’s Roofing LLC in San Antonio. Our experienced and qualified roofers know the proper techniques and regulations for your home, climate, and location. We will ensure your new metal roof provides maximum durability and protection by using only the highest-quality materials and providing exceptional customer service. From start to finish, you can trust us to install the best standing seam metal roof for your home or business.
When getting quotes for a new San Antonio metal roof, be sure to get clear specifics on what factors are driving the total price. A contractor should break down material versus labor costs for you. Understanding cost influencers helps you budget and choose the best value roof. Schedule a free roofing quote with Jimmy’s Roofing today!
