Furring strips (also called wood stripping) are not always necessary for a metal roof installation, but they are highly recommended and may be required by local building codes or the roofing manufacturer's specifications. There are several key reasons to use them:

• Energy Efficiency: Furring strips, made of wood or metal, create an air gap between the metal panels and the roof deck. This acts as a thermal break, reducing heat transfer into your home and improving overall energy efficiency.

• Moisture and Condensation Control: The air gap allows for better airflow, which helps prevent moisture buildup and condensation under the metal panels.

• Structural Support: They provide a solid, even frame to which you can attach the metal roofing panels.

It is especially important to use furring strips when installing a metal roof over existing shingles. Without them, the roof surface can be uneven, and you will experience greater solar heat gain.

You can only overlay a roof once. Any additional layers of shingles will add too much weight and may also violate building codes. Once your roof has had an overlay, you’ll need to have a full roof replacement, including a tear-off of all existing roofing materials, when it’s time for a new roof. 

Properly installed chimney flashing can last anywhere from 15 to 50 years. However, flashing generally only needs to be replaced when it is damaged, corroded, or no longer creates a watertight seal. Several factors influence its longevity, including the material type, quality of installation, and local climate. For example, copper flashing tends to last longer than galvanized steel. Large storms and extreme weather can also damage flashing, potentially requiring earlier replacement. To ensure its longevity, it is recommended to have your chimney and roof inspected annually. A professional can assess the flashing's condition and recommend any necessary repairs.

Stripping existing shingles and installing a new shingle roof takes a professional one to two days, and sometimes up to three days for larger roofs. Additional safety measures necessary for steep roofs can extend the timeframe even further, as do added measures, like replacing roof decking or reinforcing your roof structure to support heavier materials like slate or clay.