How to Install Metal Roofing Over a Bay Window

What You'll Need
Roofing Materials Identified
Screws (compatible for metal roofing)
Good Pair of Tin Snips
Utility Knife
Sheet Metal Hand Seamer/Folder
Tape Measure
Roofing Underlay

-Installing metal roofing over a bay window is not for the amateur do-it-yourselfer, but someone with a good working knowledge of roofing projects can do it without the help of a contractor. One of the most critical parts of installing the metal roof is having the correct materials and an understanding of how they differ from more common types of roofs, such as composite shingle or tile.  Do some research before starting the project to make sure you gain a good understanding of these fundamental differences, and it will make the installation process much more sensible. Carefully measure the roofing area of the window and sketch diagrams of your measurements and specifications. Take pictures of the area to be roofed from different angles. Then take all of this information with you when you go to a roofing supply store to purchase the materials. This will help the sales staff ensure that you get all of the components needed for the job.

Step 1 - Remove Old Roofing

If present, you will want to remove any existing roofing materials and take it down to the plywood. Remove all old nails, and replace any wood that is overly worn, damaged in the removal process, or rotten.

Step 2 - Lay the Underlay

Start at one side and rollout underlay horizontally, starting closest to the edge. nail down one side, roll it out, cut it, and nail down the other. Add a few extra nails to keep it snug. Roll out the nest level, keeping a six inch overlay with each row of underlay.

Step 3 - Install Flashing

Flashing, or starter edging, is installed around the eaves, using the screws identified by the roofing supplier. Follow the manufacturer's directions, but the general rule of thumb is to leave about a ¼-inch of eave hanging from the edge of eave to the start of the flashing. Screw it down in one foot intervals, placing the screws in the center of the flashing. Repeat the same process with the gable flashing.

Step 4 - Install Metal Sheeting

When installing metal sheeting, you will be working from one side to the other. Use the hand seamer to create a fold of about 1 inch on the edge of the sheet of metal. This will be slid underneath the flashing, holding the side down, then will be secured with more of the special screws identified by the supplier. Once you are started, continue per the manufacturer's directions.

Step 5 - Add Gable Flashing

Add the designated flashing to any gables that might be present (not likely in the event of a bay window), and clamp them down.

Step 6 - Install Ridge Flashing

This, too, will be style and manufacturer-specific, and instruction should be provided with the supplies.