Metal roofing - the one decision that decides everything

What is metal roofing installation?

Metal roofing installation means fastening formed steel or aluminium panels to a prepared deck over an underlayment, with the entire system - panels, clips or screws, trims, closures and flashings - working together to shed water and allow for thermal movement. The choice that matters most is standing seam versus exposed fastener: concealed-clip standing seam has no penetrations through the panel face, while exposed-fastener panels rely on gasketed screws that are a maintenance item with a finite life.

Signs you need metal roofing installation

• You are replacing a roof and expect to still be in the house in twenty-five years - the point at which metal's longer service life stops being theoretical
• You live somewhere with wildfire risk, heavy snow load, or persistent high wind, where metal's performance is a functional argument rather than an aesthetic one
• You are on your second or third asphalt roof and are tired of the cycle
• You have a low-slope section that asphalt shingles are not rated for but that a mechanically seamed metal system can handle
• You want solar later and would rather not penetrate the roof to mount it - standing seam clamps attach without drilling
• Your existing shingle roof is sound and single-layer, and an over-shingle installation is on the table

Seeing something not on this list? Browse roofing problems by symptom →

How metal roofing installation actually works

1. 1

   Panel decision, made before anything is priced

   Standing seam uses concealed clips and raised interlocking seams; exposed-fastener corrugated or ribbed panels screw straight through the face into the deck or purlins. The first costs substantially more to buy and install; the second has thousands of rubber-gasketed penetrations that will need attention.

   Watch forA quote that says "metal roof" and a price, with no panel profile, gauge, or fastening system named. That ambiguity is where the margin lives, and it is the single most common way homeowners end up with a roof they did not think they had bought.

2. 2

   Substrate - tear off, or install over the existing roof

   Metal can often go over one existing layer of asphalt using furring strips or a purlin system, saving tear-off and disposal. Full tear-off exposes the deck for inspection and repair, and produces a flatter, better-looking finished plane.

   Watch forOver-shingle installation used to avoid looking at the deck. If the existing roof has been leaking, going over it entombs wet sheathing under a sixty-year covering. Ask what evidence there is that the deck is dry.

3. 3

   Underlayment - and why it is not the same spec as under shingles

   Metal roofs get hot and cold, and condensation forms on the panel underside. A high-temperature synthetic underlayment is used, and in freeze climates an ice barrier at eaves and valleys. Some assemblies add a ventilated batten layer so the panel underside can dry.

   Watch forStandard felt under a metal roof. It degrades at the temperatures metal reaches and it is a false economy on an assembly meant to last decades.

4. 4

   Measuring and forming the panels

   Panels are cut to the exact rafter length, frequently roll-formed on site so runs are continuous with no horizontal joins. Trims, ridge caps, hip and valley flashings and closures are formed to match.

   Watch forPanels cut with an abrasive chop saw. The hot swarf embeds in the coating and rusts, leaving orange freckles across a brand new roof. Nibblers or shears are the correct tools and a metal roofer will have them.

5. 5

   Fastening - and leaving room for movement

   Metal expands and contracts appreciably along its length. Standing seam clips are designed to let panels slide; exposed-fastener screws must be driven to the right depth, compressing the washer without crushing it, in the correct position relative to the rib.

   Watch forOverdriven or underdriven screws. Crushed washers fail early; loose ones leak from day one. On a large exposed-fastener roof this is thousands of individually judged fastenings, which is exactly why installer skill matters more than panel brand here.

6. 6

   Trims, closures and penetrations

   Ridge, hip, rake, eave, valley and wall details are formed and lapped so water and wind-driven rain cannot get behind them. Foam or metal closures fill the profile at ridge and eave. Pipes and vents get purpose-made flashings, not adapted shingle boots.

   Watch forSealant doing structural work. Correctly formed and lapped trims shed water by geometry; caulk is a secondary defence with a service life. A roof held together by sealant will start leaking about the time the warranty conversation gets difficult.

7. 7

   Walk-through, touch-up and warranty registration

   The roof is checked for scratches through the coating, swarf, missed fasteners and trim gaps. You should receive the panel finish warranty, the manufacturer system warranty where applicable, and the installer's workmanship warranty separately.

   Watch forScratches touched up with any handy paint. Coating warranties are void where the finish has been breached and repaired with a non-approved product. Ask for the manufacturer touch-up pen.

What does metal roofing installation cost?

Metal roofing installs at a clear premium to asphalt - typically two to three times the price for a comparable roof, with standing seam materially above exposed fastener. Panel profile, gauge, coating and roof complexity drive it. Our cost guide breaks it down by system.

See the full metal roofing installation cost guide - by material, size and region →

If the number is the problem, here are the ways people pay for it →

Estimate your metal roof panel run and area → Squares and rafter length - the two numbers a metal quote is built from.