How to Put on Metal Roofing

Metal roofing makes a durable and aesthetically pleasing material. When installed properly, metal roofing will shield the attic from extreme solar heat and make the structure easier to cool, thereby reducing electricity costs during the summer. Made from sheets of flatstock and passed through a shaper, metal roofing can come in a variety of styles (3-channel, 4-channel, standing seam, corrugated). Many colors are available.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Tin snips
• Screw gun or drill motor with screwdriver attachment
• 1-by-4 purlins
• Grinder with cutoff wheel
• Tape measure
• Metal roofing parts
• Self-tapping roofing screws
• Rubber gasket material
• Roofing tacks
• Hammer
• 3-inch exterior screws
• Construction string

Prep Work

1. Cover the roof decking with asphalt-tar roofing felt, starting at the bottom of the roof and working your way up. Felt will come with match marks printed on the face to aid in aligning the strips of paper. The overlap should be around 6 to 8 inches. Nail every 24 inches along the top edge of the paper only so that the next layer will cover the nail heads.

2. Reinforce the valleys. Run a strip of felt from top to bottom in one uninterrupted piece. Nest the paper well into the shape of the valley being careful to not leave any hollows beneath it that may be stepped on and the paper torn. Nail the valley strips at the outer edge only to preserve the waterproof integrity of the valley.

3. Screw the purlins down with the 3-inch screws. Screw through the purlin into the rafters below. One purlin will go at the bottom of the roof at the edge to support the bottom edge of the roofing. Leave a 4-inch gap between the ends of the purlins on each run to allow air to flow between them. Place the purlins in 2-foot intervals and work your way up the roof with an extra purlin at the top to support the top edge of the roofing and the bottom of the roof cap.

Roofing

4. Starting at one end of the roof, lay out 3 sheets of roofing in series and nest the ribs together like they will be when installed. Drive a screw at the top of the rib to fasten the pieces together but not down to the purlins. Stretch the string along the bottom of the roofing metal to even the bottoms out. Use the string to project the direction of the bottom edge. Swing the metal assembly until the string comes parallel with the building, then screw the first metal strip down to the purlins with one screw between each rib on each purlin. Now you are set to run the remaining metal.

5. Unscrew the two "helper" pieces from the first sheet. Place the rubber gasket material on the leading edge of the roofing and lay the second sheet down while nesting the rib with the gasket. Screw the sheets together at the rib, about 12 inches down from the top and verify that the bottom edge is straight, according to the string. Screw the second sheet down fully and repeat the process until the roof is covered.

6. Install any valley pieces (if applicable) as you come to them. Lay a valley metal strip in one uninterrupted piece in each valley and then screw in place at the edge. Lap the roofing material over the valley metal so the roof sheds water directly into the valley.

7. Install the soffit metal at the ends of the roof. Cut the soffit to length with the snips and put a relief cut at the peak to allow the metal to fold over the peak of the roof. Screw the soffit to the roofing ribs that it lands on with the short roofing screws.

8. Cut the roof cap/ridge vent material to length and place it along the top of the ridge. Screw the bottom edges of the cap to the ribs that they land on with short screws. Do not use the foam cap gaskets provided with the roof kit as they will prevent the roof from 'breathing' and venting the heated air that is between the metal and the paper.

Tips & Warnings

• If the metal roof is going over an existing shingle roof (roof over), then disregard Step 1 and Step 2.
• Be careful when using the cut-off wheel to trim pieces. The wheel throws metal fragments as it cuts and it can bind up in the cut and shatter thus throwing bits of cutter at high speeds. Wear safety goggles or a face shield to prevent a potentially serious bodily injury. Metal roofing can be very sharp. Use caution when handling the sheets and passing them up or down to another person. Beware of damp, wet or greasy metal roofing once it is installed on a pitched roof. Shoe rubber will not gain traction on the wet metal and you may slip and slide down the roof and then fall to the ground. Walking on the heads of screws that are already installed can help, but a clean, dry roof is the safest to work on.

References

• BobVila.com: Roofing
• Roof101.com: How to Install Metal Roofing