The two metal roofing systems

Before you install metal roofing, you need to know which of the two systems you are working with, because they go on differently. Exposed fastener panels, the ribbed or corrugated sheets common on barns, sheds and budget projects, are screwed straight through the face of the panel into the roof, with the screw heads and their rubber washers visible on the surface. They are far simpler and faster to install, which is what makes them the realistic DIY option, and this guide focuses mostly on them. Standing seam panels, the premium system, interlock at raised seams that conceal the fasteners entirely, using hidden clips that let the panels expand and contract with temperature. Standing seam is sleeker and longer lasting but requires specialized tools, seaming, and expertise, and is genuinely not a beginner project.

Whichever system, metal roofing shares a logic: the panels run vertically from the eave up to the ridge, they are fastened to a sound deck (or to purlins on some structures), and the edges, ridge, valleys and penetrations are sealed with matching metal trim and flashing. Understanding your system tells you what fasteners, trim and technique you need. Our broader metal roofing guide covers choosing between the systems and the material options, while this guide walks through the installation itself.

Tools and materials

For an exposed fastener metal roof you will need the panels themselves, cut to length or ordered to length, along with the matching trim: eave trim or drip edge, gable or rake trim, ridge cap, and any valley and sidewall flashing. You will need the correct roofing screws, self tapping screws with sealing rubber washers, sized for your panels, plus closure strips (foam or metal fillers that seal the ribbed gaps at the eave and ridge), butyl tape or sealant, and underlayment for the deck. On the tool side: a drill or impact driver for the screws, tin snips and a nibbler or circular saw with a metal blade for cutting, a chalk line, a tape measure, a square, and gloves, since cut metal edges are sharp.

Safety equipment is essential, a stable ladder, a harness on anything but the lowest roofs, and good footwear, because metal can be slippery. Order about ten percent extra material to allow for cutting and mistakes, and figure your panel and screw quantities from your roof measurements, using our roofing square and measuring guide to size the job. Having everything on hand before you start, especially the right screws and the closure strips that seal the eave and ridge, prevents the mid job scramble that leads to shortcuts and leaks.

How to cut metal roofing

Cutting comes up constantly, so it deserves its own section. The key principle is to cut metal roofing cold, without heat, because heat from an abrasive grinder or a torch damages the protective coating and causes the panel to rust at the cut edge, defeating the whole point of a metal roof. For straight cuts along a panel, a circular saw fitted with a fine tooth metal cutting blade (mounted to spin so it cuts cleanly) or a specialized metal shear works well. For curves, notches and detail cuts, tin snips or an electric nibbler are the right tools. Always cut with the panel supported and secured, wear eye protection and gloves, and clear away the small metal filings afterward, since they can rust and stain the panel if left on the surface.

Avoid the common mistake of reaching for an angle grinder with an abrasive disc, which is fast but throws sparks, overheats the metal, and burns the coating at the edge, leading to rust. If you do get a raw cut edge on a coated panel, some manufacturers offer touch up paint to reseal it. Cutting neatly and cold is one of the details that separates a metal roof that lasts from one that streaks with rust in a few years, so it is worth doing right even though it takes a little longer than the quick, damaging methods.

Installing metal roofing, step by step

Here is the sequence for an exposed fastener metal roof over a solid deck.

The metal roofing sequence

Can you install metal roofing over shingles?

A frequent question is whether metal roofing can go over an existing shingle roof, and the answer is sometimes, with conditions. Metal is lightweight enough that a single layer of shingles beneath it usually does not overload the structure, and installing over shingles saves the labor and mess of a tear off. However, it is not always the right choice. Going over shingles means you cannot inspect or repair the decking beneath, so any hidden rot stays hidden and keeps spreading. The uneven shingle surface can also telegraph through some metal panels, and many installers add a layer of underlayment or thin furring strips or battens over the shingles to create a smooth, ventilated base for the metal.

Local building codes also limit how many roofing layers are allowed, so check what is permitted where you live, as our roof permits guide discusses. The honest recommendation is that a tear off is usually the better long term choice because it lets you start on a clean, inspected deck, but a properly detailed over shingle installation can be a reasonable, cost saving option on a sound roof. This is exactly the kind of judgment call worth getting a professional opinion on before you commit, since the decision affects both the cost and the longevity of the new roof.

Common metal roofing installation mistakes

Metal roofing is unforgiving of a few specific errors, and knowing them helps whether you are doing the work or checking someone else’s. The most common is fastener trouble: screws overdriven so the washer is crushed and no longer seals, underdriven so they leak, or placed in the wrong spot for the panel design. Another is ignoring thermal movement, especially on longer panels and standing seam systems, which must be allowed to expand and contract; fastening them rigidly causes buckling, the oil canning and distortion that ruins the look and can open leaks. Cutting with a grinder and burning the coating, as covered above, is a third, leading to rust at the edges.

Other frequent mistakes include skipping the closure strips at the eave and ridge, which lets in wind driven rain and pests, poor flashing at valleys and walls where caulk is substituted for proper metal detailing, and starting the first panel out of square so the whole roof drifts. Every one of these is invisible or minor on the day the roof goes on and becomes a problem later, which is the recurring theme in roofing and the reason the main house is usually best left to a crew that installs metal regularly. For the material choices behind the install, see our metal roofing guide, and for cost, our metal roof cost guide.

Why standing seam is not a DIY job

It is worth being specific about why standing seam, the premium concealed fastener system, sits firmly in professional territory even though exposed fastener panels can be a DIY project. Standing seam relies on hidden clips that attach the panels to the deck while allowing them to slide as they expand and contract with temperature, and getting that movement right is critical, since a panel fastened so it cannot move will buckle and oil can. The seams themselves must be formed or mechanically seamed precisely, often with a specialized seaming tool, to create the watertight interlock that is the whole advantage of the system. The flashing, terminations and panel layout are similarly exacting.

None of this is beyond a skilled tradesperson, but it is beyond a typical weekend do it yourselfer, and a standing seam roof installed incorrectly loses the very longevity and watertightness that justify its higher cost. This is why standing seam is almost always installed by crews trained on the specific panel system, and why we steer homeowners toward professional installation for it. If you love the standing seam look but want to keep costs down, the honest path is to get competitive professional quotes rather than to attempt it yourself, because a failed standing seam install is far more expensive than the labor you would have saved.

How long it takes and what it saves

A professional crew installs a metal roof in a comparable timeframe to other roofs, typically a few days for an average home, working efficiently with the right tools and enough hands. A do it yourself installer on a small structure like a shed or garage should budget a weekend or two, taking the time to cut cleanly, set the first panel square, and detail the trim properly rather than rushing. Metal is precise work, so the pace is deliberate, and the extended exposure of a partly finished roof to weather is a real consideration on anything larger than an outbuilding.

On savings, doing a small metal roof yourself can genuinely cut the labor cost, but the material and tools are a significant part of a metal roof’s price, so the percentage saved is smaller than with cheaper materials, and a mistake that causes a leak or forces you to re order miscut panels erodes it further. For a shed or carport the DIY savings are worth it to a capable person; for the main house, and certainly for standing seam, the value of a correct, warrantied professional install almost always wins. Our metal roof cost guide breaks down where the money goes so you can compare fairly.