How to Install a Metal Roof: A Step-by-Step Guide

How to Install a Metal Roof: The Short Answer

Learning how to install a metal roof comes down to one sequence: prepare the substrate, cover it with underlayment, and fasten panels from eave to ridge while lapping each panel over the one below it. Work from the downwind gable toward the upwind gable so wind-driven rain is pushed against the laps instead of under them. Every step after that is detail work around trim, closures, and penetrations.

The two dominant systems are the through-fastened panel, where grommeted screws pass through the panel face, and standing seam metal roof installation, where a concealed clip holds the panel and no fastener pierces the weather surface. Through-fastened profiles are cheaper and faster; standing seam handles thermal movement and low slope better.

The job order is: verify slope and deck, install underlayment and ice barrier, set eave and rake trim, lay and fasten panels, install closures, ridge cap, and penetrations, then seal and inspect. Slope drives everything, and the metal roof slope minimum for most through-fastened panels is 3:12, while standing seam is commonly used down to 1:12 or lower with the manufacturer's specified underlayment.

This guide covers both systems, the takeoff math behind them, and the cost lines you should carry in a bid. If you would rather hand the quantity work to someone who does it daily, our roofing estimating services and metal building estimating services teams price panels, trim, and fasteners from your drawings.

Metal Roofing Panel Types and Materials

Through-fastened panels are ribbed profiles with a nominal 36 in. coverage and a total width of roughly 38 to 40 in., fastened with grommeted fasteners through the flat between ribs. They are the lowest cost per square and the most common choice on shops, barns, and simple gable roofs. Because the fastener head sits on the weather surface, the washer and the fastener torque matter as much as the panel itself. These panels are typically attached directly to the roof deck or purlins.

Standing seam panels have raised legs, typically 1 in. or 1.5 in., joined with a concealed clip or a mechanical seam. They cost more per square, but they accommodate thermal expansion and contraction and perform better on low slope. The clip allows the panel to move; screwing a standing seam panel through the pan defeats the system. The roof deck must be solid and properly attached to receive the clips.

Substrate metals you will see priced: galvanized steel with a G90 or G115 coating, Galvalume (aluminum-zinc coated steel, common for unpainted roofing), aluminum (good for coastal work, no rust, but softer), zinc (long service life, high cost), and copper (premium, patinas over time, and must be isolated from steel to avoid galvanic corrosion). Each has a different scrap value, cut method, and fastener compatibility.

Panel finish matters for takeoff. Bare Galvalume, SMP (silicone-modified polyester), and PVDF (Kynar 500 or Hylar 5000) are the three finishes you will see on a quote, and the finish is often a separate line from the panel. Panel thickness is stated in gauge or in mils of coating. The standard roofing gauges are 24 ga and 26 ga; 24 ga is the default for roofs, and 26 ga is common for trim and light-duty wall panels.

Panel width and rib height also set the metal roof panel spacing on your takeoff, so confirm the manufacturer's coverage width before you divide roof area by panel width. For a clean material breakdown by profile, gauge, and finish, our material takeoff services and miscellaneous metals estimating teams build the schedule from the shop drawings, including the roof deck attachment details.

Slope, Deck and Metal Roof Underlayment Requirements

Check roof pitch with a level and a speed square before you order anything. Hold the level horizontally, measure the rise over 12 in. of run, and write the slope down. Slope determines panel type, underlayment class, and whether you can use exposed fasteners at all.

The metal roof slope minimum for through-fastened panels is generally 3:12 or greater. Below 3:12 you need standing seam, a continuous membrane, and often a fully sealed underlayment per the panel manufacturer's published detail. Some profiles are listed down to 1:12 or lower, but only with the exact underlayment and lap detail in the manufacturer's literature.

Deck options are a solid deck or open purlins. A solid deck is plywood or OSB, minimum 15/32 in. or as required by code, covered with synthetic underlayment. Open purlins, typically 2x4 or 2x6 at 24 in. on center, are common on agricultural and metal building roofs where the panels span between purlins. The panel's span rating and the purlin spacing must match.

Metal roof underlayment requirements start with a high-temperature synthetic underlayment, because asphalt felt can slump and wrinkle at the surface temperatures metal panels reach in sun. Ice and water shield is required at eaves, valleys, and in cold climates per IRC and IBC. Lap the underlayment so water always runs over the lap, and run it over the ridge rather than stopping short.

Never treat the underlayment as the roof. It is a secondary barrier; the panel is the roof. Every penetration needs a boot or a formed flashing sealed with butyl sealant, and every valley needs a proper W-valley or an open valley with the panel edges hemmed. If your scope includes the thermal and moisture package as a separate division, our thermal and moisture protection estimating and waterproofing estimating services teams can price the underlayment, ice barrier, and flashing as a line-item package.

Tools, Fasteners and Safety Before You Start

• Fasteners: Self-tapping screws with a grommeted (EPDM) washer are the standard for through-fastened panels. Length must penetrate the deck or purlin by at least 1 in. — typically 1-1/2 in. or 2 in. screws over wood deck.
• Panel clips: Standing seam uses fixed and floating clips that allow thermal expansion. The fixed clip is set near the panel center, and floating clips take the movement at the ends.
• Tools: Use a nibbler or aviation snips for cutting — never a grinder, because metal shavings rust the finish. You also need a screw gun with a depth-setting nose, a magnetic sweep, a seam crimper for snap-lock seams, and a pop riveter for trim.
• Safety: Metal panels are sharp, slick when wet, and act as a sail in wind. Use fall protection and roof jacks, and never walk a panel you have not fastened at both ends.
• Order fasteners by the square, not by the panel: metal roof fasteners per square for through-fastened panels typically run 80–120 screws per square (100 sq ft), depending on purlin spacing and wind uplift requirements. For fastener pricing and waste, see equipment cost estimating; for crew productivity, see labor cost estimating services.

Step-by-Step: How to Install Metal Roofing Panels

1. Strip or prepare the roof. Remove old ridge caps and loose material, inspect and repair the deck, and re-nail any soft spots. If you are going over shingles, see the next section.
2. Install ice and water shield and underlayment. Run ice and water shield at the eaves (minimum two courses, 36 in. up the slope) and in valleys, then roll synthetic underlayment horizontally with 6 in. side laps and 4 in. end laps, lapping downhill.
3. Set eave trim and rake trim. Install eave trim (drip edge) first, then rake trim on the gable ends, fastened to the deck or fascia with screws and butyl sealant at laps. This is the first step of metal roof trim installation and it sets the plane for everything above it.
4. Lay the first panel square. Set the first panel square to the eave and the rake; a panel that is out of square at the start will be out of square at the ridge. Fasten the first panel, then check the eave line before continuing.
5. Fasten the panels. For through-fastened panels, drive grommeted fasteners on the flat — never on the rib — at every purlin or truss, snug but not so tight the washer deforms. For standing seam metal roof installation, clip the panels at the seam and close the seam with a crimper or mechanical seamer.
6. Install closures and the ridge cap. Set closure strips at the eave and ridge to block wind-driven rain and insects, then set the ridge cap, lapping it over the panel ribs and sealing with butyl tape.
7. Flash penetrations. Flash vents, stacks, and chimneys with manufactured boots or formed flashing, and seal with butyl sealant — not silicone caulk, which fails on metal.

If you need quantities for the trim, closures, and fasteners in this sequence, a construction takeoff service can price the package before you order. For a full bid-ready roof scope, see roofing estimating services.

Metal Roof Over Shingles: What Changes

You can install a metal roof over shingles in many jurisdictions, but only if the structure can carry the added dead load and the panel manufacturer approves the assembly. Best practice is to install horizontal purlins or a nailable base over the existing shingles so the panel has a flat, straight plane. Laying panels directly on lumpy shingles telegraphs every ridge through the metal, and no amount of fastening will flatten it out.

Check local code before you commit. Some jurisdictions limit the number of roof layers — often two — and a metal-over-shingle assembly may not count as a re-roof for permit purposes, which changes the inspection and documentation you owe the building department. The other trade-off is that you lose the chance to inspect the deck. Any soft spots, rot, or previous leaks stay hidden under the new assembly, so if the shingles are curling or the deck is questionable, tear off.

Cost-wise, going over shingles saves disposal and tear-off labor but adds purlins and longer fasteners. Run both numbers — tear-off plus new underlayment versus purlins plus longer screws — before you commit. A remodeling estimating service can price both options side by side, and roofing estimating services will carry the result into a bid-ready metal roof installation cost.

Panel Spacing, Layout and Oil Canning

Metal roof panel spacing is set by the panel profile, not by you. A 36 in. coverage panel means the next panel starts 36 in. from the last, and the ribs must land on the same module at both gables. If you are working with a roofing estimating service, they will confirm the coverage width and module from the manufacturer's literature before you order.

Do the layout math before you lift a panel. Measure the eave length, divide by the coverage width, and round up. If the last panel is narrow, split the difference at both gables so the rake trim covers equally. For example, a 40 ft eave (480 in.) with 36 in. coverage gives 13.33 panels; round up to 14 panels, which means each panel covers 480 ÷ 14 = 34.29 in., so you trim the first and last panels to 34.29 in. and keep the field panels at full 36 in. coverage. That keeps the ribs on module and avoids a sliver at one end.

Oil canning is the wavy distortion you see in the flat of a panel. It comes from a wavy deck, over-driving fasteners, thermal stress, or a panel that is too wide for its gauge. It is cosmetic but owners notice it. Reduce oil canning with a flatter deck, high-temp underlayment, proper clip spacing, and by not over-tightening fasteners.

For standing seam, clip spacing is typically 12–24 in. on center depending on wind uplift and panel width. The manufacturer's span table governs, not habit. A quantity takeoff service can pull clip counts and linear foot of panel from your roof plan so the order matches the layout.

Metal Roof Trim Installation and Flashing Details

Trim is where most metal roof leaks start: eave trim, rake trim, ridge cap, hip cap, valley flashing, sidewall and endwall flashing, and transition flashing at a lower roof. Each piece has a lap direction and a fastener pattern; getting either wrong sends water behind the trim instead of over it.

Lap trim in the direction of water flow, seal laps with butyl tape or a bead of butyl sealant, and fasten with screws that do not pierce the panel's weather surface where you can avoid it. Closure strips come in two profiles: inside closure (under the panel at the eave) and outside closure (over the panel at the ridge). Use the correct one; a reversed closure is a leak waiting for a hard rain. If you are pricing trim, a gutter estimating service can help you separate eave trim from gutter and downspout costs so you do not double-count.

Penetrations: use manufactured pipe boots sized to the pipe, and for large penetrations build a curb and flash it with a soldered or sealed pan. Never rely on caulk alone. Valleys on a metal roof should be open or double-locked metal, not a single layer of underlayment; the valley carries the most water on the roof. A roofing estimating service will price valley metal by linear foot and include the extra clips and sealant the detail requires.

Fastener and Clip Schedule by System

Use this table as a starting point for takeoff, then confirm against the panel manufacturer's published span and uplift tables. Screw counts are per square (100 sq ft) of roof area, not per panel; convert panel count to squares before you order. Standing seam clip counts are driven by clip spacing and panel length; a 20 ft panel with clips at 24 in. on center takes 10 clips per seam. Add 5–10% waste on fasteners and 10% on trim; small parts disappear on a roof. A material takeoff service can convert your panel schedule into squares and apply the correct waste factor.

For a roofing estimating service, this table is the starting point for a fastener and clip takeoff; the manufacturer's span table is the final word on spacing and clip type.

Worked Example: Metal Roofing Calculator Math

Example only. Take a simple gable roof 40 ft long with a 20 ft run per side at 6:12 pitch. The slope factor for 6:12 is 1.118, so each side is 20 × 1.118 = 22.36 ft of slope length. Area per side = 40 × 22.36 = 894.4 sq ft, and both sides = 1,788.8 sq ft.

Add 10% waste: 1,788.8 × 1.10 = 1,967.7 sq ft. Divide by 100 to get squares: 19.68, so order 20 squares of panel.

Panel count: a 36 in. coverage panel running 22.36 ft needs 40 ft ÷ 3 ft = 13.33 panels per side, round to 14 per side, 28 panels total. Order 28 panels at 22 ft 6 in. length, or the next stock length up.

Fasteners: at 100 screws per square, 20 squares × 100 = 2,000 screws, plus 10% = 2,200 screws. At roughly 250 screws per 5 lb box, that is about 9 boxes.

Trim: eave trim = 2 × 40 ft = 80 linear feet; rake trim = 4 × 22.36 = 89.4 linear feet; ridge cap = 40 linear feet. Add 10% waste to each.

This is the same arithmetic a metal roofing material calculator runs; the calculator just hides the slope factor. A metal roofing calculator is only as good as the pitch and overhang numbers you feed it, so verify both against the elevations. Show the math in your bid so a reviewer can check it, and keep the takeoff on the same basis as your construction takeoff services line items. If you are pricing the full roof, the same quantities feed directly into roofing estimating services.

Metal Roof Installation Cost and Labor

Metal roof installation cost in the U.S. typically runs $8–$16 per square foot installed for through-fastened panels and $12–$25 per square foot for standing seam, depending on region, panel gauge, finish, roof complexity and access. Those ranges vary by region, scope and date, so treat them as a sanity check on your own pricing, not a bid number.

Metal roof labor cost per square typically runs $350–$700 per square, where a square is 100 sq ft, for installation labor alone. Steep slope, cut-up roofs with multiple valleys and dormers, and occupied buildings push that toward the top of the range or past it. A simple rectangular gable at 4:12 sits at the bottom.

Material is usually 45–60% of the installed price. Trim, closures, fasteners and underlayment are the lines contractors under-price most often, because they are small quantities that add up fast on a cut-up roof. Price them from the takeoff, not as a percentage of panel cost.

Tear-off, disposal, deck repair, and new purlins are separate line items. A metal-over-shingle job can save $1–$3 per square foot in tear-off and dumpster cost, but you still own the risk of hidden deck damage. For contractors bidding this work, carry labor by the square and by the piece: panels, trim pieces, closures, and penetrations each have their own production rate. Grouping labor by the square alone will underprice the trim and flashing scope, which is where most metal roof labor overruns start. Our labor cost estimating services and general contractor estimating teams build those rates into bid-ready takeoffs when you need a second set of eyes.

Common Metal Roof Installation Mistakes

• Fastening through the rib instead of the flat. On a through-fastened panel, driving a grommeted fastener into the rib crushes the rib and creates a leak path. Fasten in the flat between ribs, per the panel manufacturer's schedule.
• Over-driving screws until the grommet deforms. The washer is the seal, and a crushed washer will not seal. Set the clutch on your screw gun so the fastener seats flush without dimpling the panel.
• Cutting panels with an abrasive blade. Hot steel shavings embed in the finish and rust into it within weeks. Use a nibbler, snips, or a metal-cutting circular saw with the correct blade, and sweep the roof after every cut.
• Skipping closure strips at the eave and ridge. Without them, wind-driven rain and insects get in. Closed-cell closures go at the eave and ridge; vented closures go where the profile needs to breathe.
• Laying panels out of square from the first panel. The error compounds across the roof and leaves a wide, ugly gap at the far rake. Snap a control line off the eave and check the first panel against the rake before you commit.
• Mixing metals. Copper flashing against galvanized or Galvalume panels causes galvanic corrosion at every contact point. Keep dissimilar metals separated with the correct isolator or change the flashing material.

Most of these show up as callbacks, not failed inspections, so they are easy to miss on a punch list. If you are reviewing a roofer's bid and the scope looks thin on closures, underlayment or flashing, our estimate review services can flag the gaps before you sign. For full takeoffs on the next metal roof, start with roofing estimating services.

How Installation Differs by Project Type

The same panel profile can be installed four different ways depending on the building. Metal roof installation for contractors is rarely a single method — it is a set of methods matched to slope, substrate and budget. The five project types below cover most of the work you will bid.

Residential re-roof. Steep slope, small panels, hips, valleys, dormers and a lot of trim. Panels are short, so seams and end laps multiply, and every penetration gets a boot or a soldered pan. Labor per square is highest here, and the trim-to-panel ratio often runs higher than the panel count itself. If you are pricing this work, a residential estimating services takeoff will separate panel squares from trim linear feet so you can see where the hours actually go. The roof deck on these homes is usually plywood or OSB sheathing, and its condition can change your fastener plan.

Metal building / PEMB. Through-fastened panel over purlins, long runs, minimal trim, and the panel is often the finished ceiling. Runs are measured in hundreds of feet, so layout is fast and waste is low. This is the lowest labor per square of any metal roof type, and the metal building estimating services scope is mostly panel, fastener and closure counts. Here the roof deck is the purlin system itself, so panel attachment is direct.

Commercial low-slope. Standing seam metal roof installation over a solid roof deck or rigid insulation, held by clips rather than through-fasteners. Thermal blocks, slip sheets, and uplift requirements from the engineer drive the clip schedule, and panel lengths are often roll-formed on site. On commercial estimating services projects, the clip count and the roof deck attachment are the two lines most likely to be underbid.

Agricultural and shop buildings. Exposed-fastener panels over open purlins, often with no underlayment beyond a synthetic layer. Condensation control matters more than water shedding, so you may see a facing or a thermal break. Purlins are set by the panel manufacturer's span table, not by habit, and they serve as the roof deck.

Multi-family and mixed-use. Metal accents, mansards and canopies over framed substrates. The metal is a small share of the roof area but a large share of the coordination, because trim, transitions and waterproofing tie into other trades. On these jobs the trim and flashing scope typically drives the cost more than the panel does, and the roof deck may be wood, concrete, or metal deck.

When to Get a Professional Metal Roof Estimate

You can price a simple gable over a garage from a sketch and a supplier list. Past that point, the risk shifts from the panel to everything around it. Here is when a professional takeoff pays for itself.

Get a professional takeoff when the roof has hips, valleys, dormers or multiple transitions. Panel layout and trim counts are where bids go wrong, because a valley changes the panel cut, the closure and the flashing detail all at once. A roofing estimating services takeoff resolves those intersections on paper before you buy material.

Get one when you are bidding more than one roof at a time, or when the panel manufacturer's span table and uplift requirements must be matched to the structure. On a metal building or a commercial standing seam roof, the clip schedule and the deck attachment are engineering inputs, not field judgment calls. A construction takeoff services package gives you the quantities those decisions depend on.

Get one when the scope includes tear-off, deck repair or metal-over-shingle. Those line items are frequently missed and hard to price from a photo. You cannot see rotten sheathing, a second layer of shingles or a failed underlayment until the old roof is off, and a bid that ignores them is a bid that loses money.

A takeoff gives you panel counts, trim linear feet, fastener quantities and waste factors you can hand to a supplier for a firm quote. It also gives you a metal roofing material calculator basis: squares, linear feet of trim, clips per square, and fasteners per square, all traceable to the drawings.

Scope Precision Estimate delivers same-day quotes and bid-ready takeoffs in 24–48 hours for most projects, with rush service available and 20% off for new clients. Upload your plans through get an estimate and you will have quantities you can price metal roof labor cost per square against, line by line.