Underlayment For Metal Roofing Over Shingles

Traditionally metal roofs have used standard 30 pound felt paper underlayment.

Underlayment for metal roofing over shingles.

The purlins are screwed or nailed down to the roof deck depending on how the metal roofing manufacturer has testing for their roofing panels and then the metal is installed to the purlins. Underlayment is also a good idea when the roof is installed over battens though a natural tendency for the underlayment to drop between the battens can be a problem. Make sure the product is designed to be used under metal. This type of underlayment is critical to a quality roof installation.

If your metal roof is to be installed over solid decking or over existing shingles an environmental benefit a layer of quality underlayment between the two is essential. The best underlayment for metal roofs. Disadvantages of metal roofs. A layer of underlayment installed on top of the existing shingles will help keep the granules of the old shingles from rubbing against the back of the metal and causing possible corrosion.

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. It s installed directly on the roof deck and provides a secondary layer of protection from the elements including rain snow and wind. Roofing underlayment is what lies between the shingles and the roof sheathing or roof deck which is typically either plywood or osb. This method has its benefits as well.

This is by far the most common way to install a metal roof. The second way to install a metal roof over a shingle roof is with the use of purlins or battens. It serves as a moisture barrier as well as a slip sheet. The industry standard for underlayment is often thought of as felt paper tar paper but there are also many newer synthetic underlayments that are designed to work well with metal roofing.

Once again this is used on cold roof construction. When hot roof construction is done a roof with no ventilation a breathable underlayment is recommended. As long as the plywood under the shingle roof is in good condition this way can provide many benefits. However there are cases where you don t need an underlayment.

Metal roofs over shingles will also provide an extra layer covering your home helping to further insulate it. Underlayment must also act as a secondary weather barrier in case the roof fails. The first goal of roofing underlayment is to keep the roof deck dry before installation of the metal roofing material. 3 install 1x4 purlins down over the shingles before installing the metal roof the third way to install a metal roof over shingles is by applying 1x4 purlins over the shingle roof.

Types of roofing underlayment. Advantages of metal roofs over shingles.