Installing Metal Roof Over Shingles
Most building departments do not permit a metal roofing over shingles. The plywood underneath can rot, or even fall away and cause serious structural issues.
Installing metal over shingles can save you time and money in your roof re-roofing projects. When doing this, here are some tips you should keep in mind.
Layout
Many metal roofing contractors will recommend that you remove your old shingles before installing a metal roof. However, this is not always necessary. Installing a metal roofing over your existing shingle layer can save you money and time if the shingles are still in good condition.
It's not difficult to add an underlayment, before you place the metal roof over the shingles. Underlayments such as felt or tarpaper work well, but synthetic underlayments that don't adhere to metal panels are also available.
How to ventilate your roof is another important factor. Water vapor trapped between the shingles or metal roof can cause rust and mold if it is not ventilated properly.
This problem can be solved by installing a "framework", which is made of 2x4s, that runs parallel to your eaves. The framework creates a gap of air that prevents ice dams during winter and cools down the roof during summer. The framework also allows for the installation of ridge vents, which prevents further leakage.
Overlaps
Overlapping roofs are more resistant to wind and rain than non-overlapping ones. These roofs also offer added stability, and are resistant to pests or debris entering through the panel gaps. They are a good option for homeowners looking to reduce their maintenance costs and save money.
Your contractor should perform a thorough roof inspection before installing a metal roof. This will allow them to fix any structural issues with the existing roof. It is crucial to do this because it will help to prevent leaks or sagging if the new metal roofing is installed on top of old shingles.
The end lap of the metal panels is also important. This gap must be properly sealed to protect from reverse side corrosion due to capillary action. It is important to adhere to the advice of roofing and cladding manufactures. Seal the end lap with a waterproof silicone sealant compatible with your roof system.
Flashing
Metal roofs are not cheap. They have many advantages over shingle roofing (they are fireproof, need minimal maintenance and reflect heat instead of absorbing it). Some owners choose to add a metal roof on top of existing shingles rather than tear them off.
Underlayment is the key to installing a metal roof on top of shingles. Some contractors use tar paper, but it can adhere to metal roofing. They choose a synthetic underlayment instead.
After the underlayment has been installed, you can start laying out the panels. Pay attention to the edges of each panel, particularly where they overlap another panel. Pour prevent leakage, apply a 100 percent silicone bead along the short lip of each panel. This will seal up the overlap, preventing water from leaking into the space beneath.
Ridge Cap
Metal roofs weigh only one pound per square feet. The roof structure can therefore support a much lower load than shingles.
Many building owners are tired of the constant expense, mess and disruption to their business caused by shingles. Metal roofing is a great way to get out of the cycle of shingle replacement.
Installing metal roofing over shingles is possible, but it must be done properly to ensure that the roof works correctly and to prevent moisture from building up between the two layers. Installing a wooden plank of a quarter inch thickness on top of the asphalt roof is required before the metal panels can be installed. It creates a cushion of air to reduce the chances of denting the roof and prevent condensation. Planks can either be solid or vented, allowing for a ridge ventilation. This vent is vital to the proper function of the roof, so it is important that you choose carefully depending on the climate in which the roof will be located.
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Most building departments do not permit a metal roofing over shingles. The plywood underneath can rot, or even fall away and cause serious structural issues. Installing metal over shingles can save you time and money in your roof re-roofing projects. When doing this, here are some tips you should keep in mind. Layout Many metal…