Cutting Metal Siding and Metal Roofing: Our Do-it-youself How to Tips



The basics of working with metal siding or metal roofing is really not that difficult; however after working with it for a few years, I do have some tips that first-time users might find useful. Metal siding is as easy to work with as any other siding material. There are different rib styles and weights, but it all cuts in a similar fashion. All that is needed to make professional straight cuts on metal siding is a pair of tin snips, a level, a chalk line, and utility knife.

Cutting Across the Ribs

For making straight cuts, one needs a good pair of sharp tin snips that have a cutting edge of 3 inches or so. The shorter ones work well for going around corners and trimming short cuts, but not for good, straight smooth cuts across the sheets of metal. First, of course, you need to know where to cut. Measure length and make pencil marks, on top of the ribs, on the metal. Holding the level back the width of the wood of the pencil from your marks, use the level to keep the pencil at a ninety to the metal and complete a line across the metal. Doing that will insure your mark is the same from the top of the rib to the bottom and across the flat as you mark. Don't waste a whole lot of time trying to make marks up the sides of the ribs, there is plenty to guide you with just the mark on the top and across the flat. (For ease of writing I will use a right-handed perspective for explainging the cutting.) Start by laying the metal on the ground --preferably a flat surface. Grasp the metal above your line with your left hand and cut, with the tin snips in your right hand, up and across the top of the first rib. Then place your right foot on the sheet below the line. Don't step down too hard or you will flatten the rib, but keep enough pressure that the metal can not come up as you pull. Once you get past the first rib you can safely pull the cut side up away from the ground. You may have to pull hard with your left hand, and it may surprise you how hard you can pull the metal without damaging it. It is possible to pull too hard and damage the metal, but it does requite a lot of strength. The harder you pull, the easier it is to cut the metal with the tin snips. Continue pulling up, cutting, and holding down with your foot. When installing metal roofing, you may wish to put the cut edge up under the ridge and keep the factory cut for the exposed edges.

When Using Tin Snips

Don't close the snips entirely. If you do, then the end will stretch the metal as it is forced through and will cause a little serration. Also, make sure you keep forward pressure on the snips (Not HARD), if you don't, then you will keep making new cuts and will get little half-circle flesh hooks on the edges of your metal sheets. As necessary, you can get a lower grip on the metal, and move your foot from the rib on the edge of the metal, to the flats between the ribs as you cut. Once you get to the last rib, you have to not pull up as hard or you will bend the metal siding.

Cutting straight lengthwise

If possible, score metal siding along one of the ribs or the slight bump on the flat. Use a good, sharp utility knife and score the metal. To score straight is very hard unless you have something to guide the blade, hence the rib or bump. Score along the top of the metal then bend it away from the score, the metal will break the rest of the way. You may need more than one person to help you bend the metal evenly enough to keep it from bending and yet enough to break over. If you are scoring off just one rib, it is easier to cut every 16 inches or so up to the score and break off the pieces one at a time. Care should be taken when making the cuts. Do not go past your score or you will get serrations on the edges of the metal. If you need a length that is in between the ribs or bumps then first score down the rib using the this method, then you can snap a line and carefully cut with ten snips in the above described manner to get the exact width you need.

When the blade gets dull

You can break off the tip, and continue using a razor-blade utility knife when scoring metal siding because the only part of the blade that dulls is the tip. Of course, if someone comes along and finds your knife, they might try to be thoughtful and change out your blade for a new one!