When it comes time to install metal roofing there is one basic rule of thumb. If you can't easily walk across the roof because it is too steep, call a professional. Now that the rule is out of the way, if you have a building that needs a metal roof but the professional bids are too high, here is how to install it.
First the proper tools are needed. These include a measuring tape, a chalk line with plenty of chalk, a good drill, a safe extension ladder and a good, sturdy step ladder, pound of inch roofing nails, metal roofing screws, metal snips, and to hold the nails and screws a nail bag.
Using the tape measure the roof's height adding the desired overhang, generally two to four inches. Take accurate measurements keeping in mind the handy man's mantra "measure twice, cut once." Now measure the roof's length and height on both sides to estimate how much metal edging is needed. Give these measurements to your roofing supply company. They will tell you how much roofing to purchase. Keep in mind that three to six inches of unblocked air flow is needed between layers.
Although it is not necessary to remove the old roof before laying down a metal roof, it is best. Use a pitch fork, roofing shovel, or roofing pliers to remove old shingles. Then lay down 30 pound tar paper to serve as the base for the new roof. If there is only one layer of shingles on the old roof, lay down 1"x4"x building length pine wood boards screwed onto the old shingles. Once the roof is prepared the metal roof edging can be applied.
Now it's time to place the metal sheets running from top to bottom rather than side to side. They are screwed into the wood slats, using a screw every two feet on both sides of the sheet. Each sheet overlaps the last. When you reach the edge cut the last metal sheet so it is just past the edge of the roof.
When the sheets are applied to both sides of the roof it's time to apply the metal trim along the edges at the sides of the roof. The trim also goes on the peak, first scoring it in the middle so it can be bent over the peak.
That covers installing the tin barn roof type of metal roof. Methods for installing other types of metal roofs can be found on the Internet. But those can be tackled equally as well by a do it yourself person who wants to install metal roofing.