Metal Roof Directly Over Shingles

Advantages of metal roofs over shingles.

Metal roof directly over shingles.

Metal roofs over shingles will also provide an extra layer covering your home helping to further insulate it. A metal roof is an alternative to a shingle covered roof but a metal roof can actually be installed over shingles. By placing metal roofing over shingles you can save in the labor costs of ripping them off while also preventing them from being thrown into landfills. The purlins are screwed or nailed down to the roof deck depending on how the metal roofing manufacture has testing for their roofing panels and then the metal is installed to the purlins.

There are really two ways to install a metal roof over a shingle roof. The first way is to run new underlayment over the existing shingle roof completely covering the old roof. The second way to install a metal roof over a shingle roof is with the use of purlins or battens. Metal roofing weighs less than one pound per square foot.

Asphalt shingles can weigh up to four pounds per square foot depending on the brand. If you don t want to take our word for it check with your local building department. The first one being that the new underlayment will act as a second line of defense in case water would to somehow get underneath the metal roof. The vast majority of installations of the metal roofing systems produced by my company are over existing shingles.

My perspective pertains primarily to metal shingle roofs which are more forgiving of going over uneven surfaces than are some vertical seam metal roofs. First because the frame is screwed directly to the rafters and the interlocked shingles are screwed to the frame the roof can withstand winds of up to 120 mph without damage. Metal is the best choice due to its very low weight per square foot and its unique design. Otherwise you will need to remove the shingles.

However you should only install a metal roof over shingles if you have less than four layers of shingles on the roof. This provides a couple of benefits. The low weight of metal roofing is one thing that encourages this. Disadvantages of metal roofs.

It provides a solid flat surface to attach the new metal roof to it creates an air gap between the back of the metal and the shingle roof which allows for airflow. Second the frame creates a flat and straight surface even when the shingles are badly curled or the roof ridge is bowed. This method has its benefits as well.