A frequent question many roofers get is whether it is possible to install metal roofing over shingles. Not only is it possible to install a metal roof over an older shingle roof, but it also carries several significant advantages. For one, by not having to tear down and dispose the old roof, you’ll save on labor and moving costs. For another, the additional layer of roofing will add to the insulation of your building.
If you want to install a new roof over an older one, then metal roofing over shingles is the best option because metal is light weight and does not need any reinforcing of the underlayment and roof frame. Weight for weight, metal roofs are only a quarter as heavy as asphalt shingle. And in certain jurisdictions, this factor is built into the regulations with only a single layer of shingles being permitted if metal roofing over shingles is planned.
The point to remember is that if your new roof is designed to support the load of the new roof and transmit it directly to the ground, without relying upon an existing roof or covering for support, then you will not need to remove the existing leaky roof. This is what you do with a standing seam metal roof anyway.
Before going ahead with the new metal roofing over shingles, there are some preparations you must make. Any existing roof leaks must be fixed. If there are broken shingles or rotten wood frame, then fixing them now will help prevent further damage later on. Extremely heavy roofing materials are better partially removed, as the overall weight of the new roof will be lowered.
You could also work around this by strengthening the framework through an extra layer of underlayment or a reinforcement of the roof frame. If you plan to use tar paper for this purpose, keep in mind that tar sticks to the undersurface of your metal roofing over shingles and can cause problems later. Bubble wrap makes for a good underlayment, and there are other options made of synthetic material.
Once you’ve completed these steps, you’re ready for metal roofing over shingles. Step by step, here is the process. Please be informed that this is not a definitive guide or a step by step tutorial, and no claims are being made about the reliability or authenticity of this information. When you engage upon a do-it-yourself project, be sure to take safety precautions and check with your local roofing contractor about circumstances unique to your roof.
First your roofing contractor will create a base over the shingles using lengths of wooden board separated by a couple of feet all over your old shingles roof. These can be fixed firmly to the old roof itself by using screws in each edge of the board. It’s generally a good sequence to work your way to the top starting from the bottom.
Next comes the metal edging. This goes all around the roof, creating a perimeter for it. The metal edging is attached to the roof securely with long nails. Then the metal roofing sheets are fixed. Each sheet is laid over the roof and fixed in place before the next one is placed slightly overlapping it. Screws are ideally placed every 24 inches or so to provide the most secure attachment.
Some roofers insist on making sure that the screws are also overlapping. This is to prevent wind and weather related damage as well as water leaks. The entire roof area is covered with metal sheets, with screws that hold the overlapping metal roofing sheets securely together. This is an important step of metal roofing over shingles.
Finally, the metal trim is fixed in place around the edge of the roof, and also on the ridge at the top of your roof. Like the perimeter, the metal trim is fixed by screws every 24 inches or so. The metal is bent over the ridge to provide secure seal against water, snow and ice. The bottom of the metal sheets isn’t fixed to anything, so it is simply folded back and attached to the roof’s edge with screws.
Closures which are coated on one side with self-sealing adhesive can be inserted into any gaps, where they will stick and seal off any gaps. Insects and elements will be kept out in this way.
By providing a safe and secure cover for your building a metal roofing over shingles project can save you money, enhance your insulation and protection, and also be done without seriously inconveniencing you or the people who live and work inside the building because there is no tearing down involved. These advantages make it attractive to home owners who opt for a metal roofing over shingles arrangement when it comes time to replace a worn out asphalt shingle roof.