What are the main steps to install a metal roof?
To install a metal roof, you install eave and rake trim, roll out underlayment, set the first panel square to the eave, fasten at the specified spacing, overlap each panel, then fit closures, ridge cap and flashing. Panel type, pitch and substrate set the fastening pattern.
Measure and Order: Takeoff Numbers You Can Trace
Every order starts with roof area in squares, where one square equals 100 sq ft of roof surface, not floor area. Measure the footprint from the plan, then divide by the cosine of the roof pitch to get the sloped area. A 40 ft by 30 ft footprint is 1,200 sq ft of plan area; at a 6:12 pitch the slope factor is about 1.118, so the roof area is 1,200 × 1.118 = 1,342 sq ft, or 13.42 squares. Field measure the same way with the actual overhang included.
Panel length math follows the slope: measure from the eave line to the ridge along the roof surface, add the eave overhang and any ridge allowance the profile needs, and round to the manufacturer's increment. Keep each panel run on one line of the takeoff so a reader can re-check length, count, and total linear feet.
Waste is a judgment call, not a fixed rule. Typical waste on a simple gable runs low single digits; hips, valleys, and dormers push it higher. Add trim as linear feet, not squares: eave trim equals eave length, rake trim equals rake length, ridge cap equals ridge length, and closure strip follows the same runs. Count fasteners from the manufacturer's pattern — screws per square foot of panel times panel area, plus clips at the clip spacing.
This is where metal roofing panel installation and the diy metal roof vs contractor decision separate. A DIY crew saves labor but owns the takeoff errors, and a short panel order is a second delivery. An exposed fastener panel with a simple gable is the friendliest first job; standing seam with valleys is not. The same discipline carries into larger assemblies, which is why metal building and pemb estimating treats purlin runs and panel counts as separate lines. For a structured walk-through of the measuring method, see how to estimate roofing. The square-foot budget calculator below takes your own base hard cost per sq ft and applies soft-cost, contingency, and escalation percentages — it holds no prices of its own, so the numbers come from your takeoff.
| Item | Unit | Quantity | Arithmetic |
|---|---|---|---|
| Plan area | sq ft | 1,200 | 40 ft × 30 ft |
| Slope factor | — | 1.118 | 6:12 pitch |
| Roof area | sq ft | 1,342 | 1,200 × 1.118 |
| Roof area | squares | 13.42 | 1,342 ÷ 100 |
| Waste at 8% | squares | 1.07 | 13.42 × 0.08 |
| Order quantity | squares | 14.49 | 13.42 + 1.07 |
| Ridge cap | linear ft | 40 | ridge length |
| Eave trim | linear ft | 80 | two 40 ft eaves |
Square-foot budget calculator
- Hard cost
- $444,000
- Soft costs
- $53,280
- Contingency
- $49,728
- Escalation
- $21,880
- Budget total
- $568,888
- All-in per sq ft
- $237
Enter your own base rate from a recent bid, cost book or estimator. The default values are placeholders for the math, not market prices.
Roof area, slope, and panel length math
Write the arithmetic on the takeoff sheet so the number is traceable: footprint length × width, then × slope factor, then ÷ 100 for squares. For panel length, use the raked distance from drip edge to ridge plus overhang, and note the pitch and the measurement date. If you are working from a plan, cross-check the roof deck dimensions against the wall dimensions before you trust either. Knowing how to install a metal roof starts with knowing exactly how many squares and linear feet of trim the roof holds, because the panel order is cut once.
Waste, trim, and fastener quantities
List waste as a separate line with its percentage and the reason, so a reviewer can challenge it. Trim quantities come from measured runs: eave, rake, ridge, hip, valley, and wall transitions each get a length and a piece count. Fasteners get a count per square from the panel manufacturer's pattern, then multiplied by squares and rounded up to the box. A quantity takeoff built this way survives a change order because every line shows its unit and source, and it gives a general contractor a defensible basis for how to estimate construction projects as a general contractor.
Prep the Deck, Underlayment, and Flashing
Deck preparation is the cheapest insurance on the job. Renail or re-screw loose sheathing, replace delaminated panels, and check that the roof deck is flat enough for the panel profile — standing seam metal roof installation shows every dip as oil canning. Where the panel spans purlins instead of solid deck, set purlin spacing from the manufacturer's span table for the panel gauge and design load, and keep the purlins straight and in plane.
Ventilation belongs in this stage. Confirm intake at the eave and exhaust at the ridge before the ridge cap closes the roof, because retrofitting vent after the panels are on is a demolition task. On a re-roof over shingles, the substrate has to be built up so the new panel plane is true; the old shingle course is not a flat surface.
Underlayment laps follow the slope: higher laps over lower, with the lap width from the manufacturer's instructions. Synthetic underlayment is the common choice over a full deck; ice and water shield goes at the eaves, in valleys, and around penetrations where the code edition requires it. Fasten through the underlayment into the deck, not into the previous layer.
Flashing order follows water: valley flashing first, then eave and drip edge, then wall and step flashing woven with the panels, then pipe boots and other penetrations. Each panel overlap at a transition should shed onto the piece below it. Any guide on how to install a metal roof spends most of its length here, because on a cut-up roof the field goes fast and the transitions do not. Our professional trade estimating services price these stages as separate line items so the labor is visible.
| Step | Component | Unit | Rule of thumb |
|---|---|---|---|
| 1 | Valley flashing | linear ft | Set before panels, full length |
| 2 | Ice/water shield at eave | linear ft | Self-adhered, confirm extent with code |
| 3 | Synthetic underlayment | squares | Laps shed downhill |
| 4 | Drip edge and eave trim | linear ft | Straight line for panel start |
| 5 | Panels and panel clips | squares | Clip spacing per span table |
| 6 | Step and wall flashing | linear ft | Woven with each panel course |
| 7 | Pipe boots and penetrations | each | Collar seated on profile |
| 8 | Ridge cap and closure strip | linear ft | Vent path left open |
Decking, purlins, and ventilation
On solid deck, the sheathing carries the clips and the underlayment; on purlins, the panel spans between supports and the spacing is a structural number, not a preference. Check fastener embedment into the deck and the purlin gauge against the panel manufacturer's table. Ridge vent and eave intake are set before the ridge cap goes on, and the closure strip at the ridge must not block the vent path.
Synthetic underlayment and ice/water shield
Roll synthetic underlayment horizontally with laps facing downhill and stagger the end laps. Ice and water shield is a self-adhering membrane at the eave, in valleys, and around penetrations; confirm the required extent with the local building department, since code editions differ. Walk the membrane down by hand or roller so it bonds — a loose lap is a future leak path.
Valley, eave, and wall flashing
Valley flashing goes in before any panel and must be wide enough to take the panel edge plus the lap. Eave trim and drip edge set the panel start line, so check them for straight before the first panel goes down. Wall and step flashing are woven as each panel course is set, and pipe boots go on after the panel is fastened, with the boot collar seated on the profile. This is the stage where how to install a metal roof is decided in practice: the flashing sequence, not the panel count, sets the pace.
Install the Panels, Fasteners, and Trim
Before the first panel goes up, snap a chalk line at the eave parallel to the ridge and check it against the rake on both ends. A panel that starts out of square compounds across the whole run, and it shows up later as a widening gap at the rake trim. Set the first panel, check the eave overhang and the line, then fasten it and use it as the reference for every panel after it.
Work from the manufacturer's published installation manual, not from memory or a supplier's verbal advice. The manual states panel gauge, clip or screw spacing, fastener type, and the maximum span over purlins for your wind zone. Those figures are what an inspector and a warranty administrator will check, so keep the manual on site and note the revision date on your daily log.
A concealed fastener system hides the clips under the seam, while an exposed fastener panel drives screws through the face. Both depend on the same discipline: correct fastener spacing, correct torque, and a straight run. If you are weighing a panel upgrade mid-project, the point to decide is before the deck is covered, which ties into the replacement triggers covered below.
Panel alignment, overlap, and clip spacing
For standing seam, place a panel clip at every purlin or as the manual directs, typically no more than 24 inches on center along the seam, and set each panel fully engaged before moving on. The metal roof panel overlap and fastening pattern for exposed fastener panels usually runs one major rib plus one minor rib, with screws on the flat between ribs. Fasten from the eave toward the ridge so panels can move outward at the eave under thermal movement. Never stretch a panel to close a gap; lift it and re-set the line.
Fastener placement and torque
Drive self-drilling screws with a gasketed washer straight and perpendicular, so the washer compresses evenly without cupping or splitting. Over-torque crushes the washer and leaves a path for water; under-torque leaves the washer loose. On exposed fastener panels, screws go in the flat of the panel, not in the rib, unless the manual says otherwise. Set a clutch on the driver and test the first few screws on scrap panel before you commit to a full run.
Ridge, hip, rake, and penetration details
Ridge cap, rake trim, and eave trim each need a closure strip or profile filler matched to the panel so wind-driven rain cannot enter under the trim. Seal pipe boots and other penetrations with the boot's own flashing and a bead of sealant under the flange, then fasten the flange with pancake screws into the deck. Leave the lower edge of each trim piece open where the manual calls for drainage, and check every lap so water runs over the lower piece, never behind it.
Cost, Inspection, and What to Verify Before You Pay
A metal roof estimate should read like a bill of materials, not a single lump sum. Ask for the panel type and gauge, the trim schedule, the underlayment product, the fastener type and count, labor hours, equipment, and disposal. When an item is missing, the contractor either forgot it or plans to add it later as a change order. A traceable takeoff through a quantity takeoff keeps each of those lines tied to a measured area and a stated rule.
Material prices move. Steel mill products rose sharply in the twelve months to the latest Producer Price Index reading, and plastic construction products and lumber also moved, which is why a panel quote from last quarter may not hold. Labor rates for roofers and sheet metal workers come from published wage data. That is why we price from national average unit costs adjusted with those published series and reviewed by an estimator.
To start, request a free quote and attach your drawings.
Line items that belong in a metal roof estimate
Panels are priced per square of covered roof, with waste added for hips, valleys, and short runs. Trim and flashing are priced by the linear foot: rake trim, eave trim, ridge cap, valley flashing, and each pipe boot. Underlayment is priced by the square, with ice and water shield at the eaves and valleys. Fasteners are counted by type, including the gasketed washer screws and the pancake screws for trim. Labor, equipment, and tear-off disposal are separate lines. Commonly omitted items include closure strips, touch-up paint, and the purlin or furring needed to correct an uneven substrate.
Final inspection and warranty paperwork
Walk the finished roof with the contractor and check fastener lines for straightness, trim laps for direction, and every penetration for a sealed flange. Look for oil canning across the panel field, which is a flatness issue rather than a leak, and confirm the contractor documented it before installation. Confirm the metal roof underlayment and fasteners match the spec sheet, and that the metal roof trim and flashing installation was done to the manual. Register the manufacturer's warranty in your name, keep the panel and fastener invoices, and hold final payment until the punch list is closed and the warranty certificate is in hand.
Frequently Asked Questions
How much does it cost to install a metal roof per square foot?
There is no single national rate, because the number per square is built from the panel type, gauge, seam spacing, trim count, deck condition and tear-off scope. Standing seam with concealed clips and a full underlayment system prices differently from an exposed fastener panel screwed through the ribs. We quote the fee per project after reviewing the plans, and the estimate shows each line with its unit and source.
Can you install metal roofing over existing shingles?
Sometimes, but the decision is made on the deck, not on the shingles. A common approach is to strip the old covering, inspect and repair the roof deck, then lay synthetic underlayment or ice and water shield before the panels. Building over an existing layer adds weight and hides rot, so confirm what your local code and the panel manufacturer allow before you order material.
How long does a metal roof last compared to asphalt shingles?
Service life depends on panel gauge, coating, fastener type and climate, so treat any single number with caution. Asphalt shingles are commonly replaced far sooner than a properly detailed metal roof, and exposed fastener panels need washer and screw checks that standing seam does not. Salt air, hail and roof pitch all move the answer, so ask the manufacturer for the warranty terms on the specific panel.
What is the difference between exposed fastener and standing seam metal roofing?
Exposed fastener panels are screwed through the face of the sheet with gasketed washers, so the fastener is visible and the panel is cheaper to install. Standing seam panels use concealed clips and raised seams crimped together, which lets the metal move with thermal expansion and leaves no fastener through the weather surface. Standing seam costs more per square but carries fewer penetration points to maintain.
How do you know when it's time to replace a metal roof instead of repairing it?
Replace when the failure is systemic: widespread fastener back-out, rust through the panel, failed washers across whole runs, or seams that no longer close. A single lifted panel, a torn pipe boot or a local flashing leak is a repair. Check the underside for water staining and the fasteners for loose or missing screws before you decide, and price the repair against a full replacement.
What fasteners and underlayment are required for a metal roof installation?
Use self-drilling screws with gasketed washers sized to the panel and substrate, plus pancake screws for trim and closure strips at the eave and ridge. Underlayment is typically synthetic or felt over the deck, with ice and water shield at eaves, valleys and penetrations. The panel manufacturer's installation manual governs screw spacing and underlayment type, so follow that document and the local code edition.
How long does a metal roof installation take?
Duration is set by roof area in squares, panel length, trim and flashing count, deck repairs and weather, not by a standard schedule. Long panels that arrive pre-cut to the eave-to-ridge length go faster than field-cut sheets, and a tear-off adds a full day or more on many homes. We confirm the delivery date with the quote rather than promising one in advance.
How do you plan the panel layout before you learn how to install a metal roof?
Start with a measured takeoff: eave-to-ridge length in feet, total roof area in squares, panel width after overlap, and a count of ridge, eave, rake and valley trim in linear feet. Divide the eave width by the effective panel coverage to get the panel count, then add the manufacturer's waste allowance. That sheet is what you order from, and it is what keeps the installation sequence from stalling mid-roof.