Prepare the roofing
This is the first thing that you should do. Here you need to clean the roof so that you can get rid of any dirt and debris. You should also check the sheathing for any nails or screws that might be loose.
As rule of thumb all nails and screws should be below the sheathing surface. If there are any loose nails or screws, you should put them in place before you continue with the installation.
You should note that the roofing is very pliant and flexible in cold weather and can easily crack and break if it’s manipulated while cold. Due to this you should not install it in cold weather. If you have to install it in cold weather, you should cut it into sheets of 12-18 feet and lay them flat in the garage to warm up.
Although you don’t have to place it, the underlay provides an extra layer of protection. Here you only need to cut a strip of underlayment that is of the same length as the roof. Once you have cut it you should place it under the roof and attach it using nails.
For ideal results you should ensure that the nails are 6-8 inches apart. You should also ensure that the surface of your underlayment is smooth and wrinkle-free.
Install the roofing
You need to measure and mark 35 inches from the bottom edge of the roof sheathing in several spots. You should use chalk to mark the spots. After doing this you should roll out the roofing and cut it so that it covers the entire length of the roof.
When cutting, you should place the top edge of the roofing along the chalk line. This is to allow an overhang of one inch on the eaves.
You should then apply two inches of cement under each side in order to seal the roofing down. After doing this you should nail the roof while ensuring that it stays flat and even.
You should do the same to all the sheets that you want to install. Once you are through with the installation you should use a utility knife to trim away any excess overhang. You should also ensure that all overlaps are covered with cement.