Tips For Installing A New Metal Roof Over Asbestos-Containing Slate Tiles

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If your home has an aging roof that is made of asbestos-containing slate tiles and it needs to be replaced, then you can likely install new roofing materials right over the top of it and encapsulate the asbestos. Encapsulating the asbestos-containing materials under new metal roofing panels renders them safe and is always better than stripping off the old slate tiles when it is possible to do so. To install a new roof over the top of your worn out asbestos-containing roof, follow these important tips:

Tip: Test the Roof for Stability and Check Local Building Codes Before Replacing Your Roof

Before you can install your new metal roof, first you must check the stability of your roof structure to make sure it can hold the additional weight of the metal roofing panels. Typically, roof rafters are built to withstand the weight of two layers of roofing materials. If you are unsure, a local residential roofing contractor can advise you.

Since your new roof will likely require a building permit, you should check with your county's building inspector's office to determine if the local building code will allow you to encapsulate your old roof under metal roofing panels.

Tip: Use Stainless Steel, Self-Drilling, Self-Tapping Screws to Attach the New Roofing Materials

When attaching metal roofing over asbestos-containing tiles, you should use stainless steel, self-drilling, self-tapping screws. This type of screw will go through the old tiles the easiest and will lessen the chances of broken tiles as you install the metal roofing.

Tip: Attach the New Roofing Material and Underlayment with the Same Screws

Between your new metal roofing panels and the existing roof, you need to install an insulating underlayment. While you would generally install the underlayment first and then roof over it, when you are installing a metal roof over older asbestos-containing tiles, you should attach both materials at the same time. This procedure will lessen the breakage of tiles as you do the installation and will release less asbestos fibers into the air as you work.

Tip: Use Appropriate Flashing Material to Encapsulate the Gables and Eaves

Finally, the eaves and gables on your roof need to have metal flashing installed on them to encapsulate the old asbestos-containing roofing materials. The gable and eave flashing must wrap around the edge of the roof and seal the asbestos-containing roofing tiles between the new roof and the siding on your home.  

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