- The first step in building a steel roof vent is to pick a design that suits your roof. There are three major types: the standard J-vent, a J-vent that has additional clearance and Dormer vents. Where the vent is going should dictate the one you choose. A J-vent is ideal for regular pitched roofs or a flat roof. Dormer vents go on dormers. Consider the position of the vent, what is being vented and how much clearance you will need. Also be aware of the debris that can fall and get into the vent.
- The next step is to build the vent. Typical roof vents are made from aluminum, the same type of material that is used in flashing. So get enough material to construct your roof vent. You should also decide how it is going to be installed. Usually, the roof vent installs with a flat bottom piece that secures to the roof plywood, under the shingles. The shingles are placed around the vent itself.
- To properly cut and size your metal follow your design carefully. Always leave a little extra material when you make a cut because you can easily trim down, you can't add metal once cut. You should cut a square that is the height of the vent tube and long enough to roll into the diameter or tube you need. Also cut a very large, oversized single sheet to make the roof vent top from. Next cut a square of metal for the bottom. It should be about 1 foot by 1 foot wide for a 4- to 6-inch diameter vent. Check any safety and building regulations on this dimension (if any) to be sure you are building to code.
- Once the pieces are cut, it is time to shape them. The first step is to roll the metal to form the vent hole. Then take a large piece of metal sheeting and shape down the sides using a mallet and pounding tool until you have the desired J-vent shape. This top piece can be soldered right on to the top of the vent tube. Now place the vent tube centered on the bottom sheet. Draw a line around the tube with a pencil and cut out the hole. The vent tube can then be soldered onto the bottom sheet.
