How to put on a metal roof: panels, trim and screws, with the cost for a garage

Exposed-fastener or standing seam: which metal roof to install

For a DIY garage, exposed-fastener panels are the ones you can put on with a drill, and they are what this guide prices. An exposed-fastener panel, such as Pro-Rib, is screwed through its face into the deck or purlins, with a rubber washer sealing each hole. It goes on with a drill, and the screws are the maintenance item. Standing seam hides its fasteners in clips or a flange under the next panel's seam, so nothing punctures the weather surface. The snap-lock and mechanically seamed versions also need more precise layout, because the seams only close when the panels run true.

The code treats them differently on slope. IRC R905.10.2 allows lapped exposed-fastener panels down to 3/12 without sealant and down to 1/2:12 with lap sealant applied per the maker's instructions. Standing seam can go down to 1/4:12. Makers can be stricter than the code: Fabral's manual asks for at least 2 1/2 in per foot on its exposed-fastener profiles, and Midwest Manufacturing, which makes the Pro-Rib panels Menards sells, requires tape and lap sealant on every lap below 3/12.

This guide prices Pro-Rib: 36 in of coverage per panel, 3/4 in ribs, steel 0.0142 in thick before paint (29 gauge), G60 galvanizing and a 40-year limited paint warranty. Menards listed it at $127.49 per 100 sq ft on 2026-09-19, figured on the 38 in nominal width, and cuts it to any length from 2 ft to 36 ft in 1 in steps. Cut to length, one panel runs eave to ridge with no end laps on a garage this size.

Can you put a metal roof over shingles? What the code allows

Often, yes: over one dry layer of shingles, installed per the panel maker's instructions, but never over two layers, a water-soaked roof or tile. IRC R908.3 defines a replacement as removal down to the deck. R908.3.1 permits a recover, new covering over old, when the new covering goes on per the maker's instructions, and it says standing-seam systems that carry their loads to the structure don't require removing the old roof. R908.3.1.1 then shuts the door in three cases: a water-soaked or deteriorated roof, an existing covering of slate, clay, cement or asbestos-cement tile, and a roof that already has two or more layers.

Screwing panels straight through shingles into the deck is where the maker's instructions come in. Fabral's manual says that where existing shingles stay in place, new 2x4 purlins should be fastened through the decking into the rafters, and it recommends purlins no more than 24 in apart. Midwest's UL-tested Pro-Rib assembly also uses 2x4 lathing at 24 in on center as its alternative to a plywood deck. On the garage below that means 8 rows of purlins on each side, 16 rows of 32 ft, 512 lineal feet of 2x4.

NIST puts laminated shingles at about 280 lb per square, so 8.77 squares is 1.23 tons. At the City of Fargo's published rates of $120 a haul plus $57 a ton, disposal comes to $189.99. For that you get to see the deck, and Pro-Rib's 40-year paint warranty ends up sitting on top of whatever is under it. This guide prices the tear-off.

The garage being roofed, measured

A detached garage, 30 ft by 24 ft at the walls, 12 in overhangs all around, a 4/12 gable with one layer of shingles and no penetrations. The roofing calculator's geometry gives:

Panel length is the slope length plus the eave overhang. Midwest's guide allows the panel to hang 3/4 in to 3 in past the roof edge, so 164.4 in plus about 1 in rounds to 165 in: order 13 ft 9 in panels. Each covers 36 in, and 32 ft of eave takes 10.67 panels, so 11 per side, 22 in all. At 4/12 the roof is above the 3/12 line, so the laps don't need sealant by code or by Midwest's guide.

Metal roofing material list and prices

The screw count follows Midwest's UL Construction 560 for Pro-Rib: screws every 24 in along the panel, 9 in apart across it, and at each panel end on both sides of every major rib. On a 13 ft 9 in panel that is two end rows of 8 and six intermediate rows of 4, 40 screws a panel. Fabral's manual budgets 80 screws per square for its similar profile, which would be 702 here. Use the pattern the panel you buy was tested with, and buy the extra box.

Tools

You need a drill/driver with a clutch and a hex bit. Midwest says not to use an impact driver on panel screws, because it overdrives the washer and chews the paint, and to drive into wood at about 2,500 RPM. Cut with tin snips or panel shears; Midwest says not to use a circular saw. Add a chalk line, a tape, a hand seamer for trim, a ladder that clears the eave by 3 ft, and fall protection ($114.99 for a kit).

Fall protection comes before the first panel. OSHA's residential rule, 29 CFR 1926.501(b)(13), requires a guardrail, a safety net or a personal fall arrest system for workers 6 ft or more above a lower level. The rule binds employers only, and a garage eave is already past 6 ft, so hold yourself to it. Set a roof anchor and wear the harness, stay off wet or dewy steel, which is slick, and do not walk panels before they are fastened. If you won't tie off, hire the roofer.

Step by step: how to install a metal roof

1. Tear off the shingles and old underlayment, pull or drive every nail flush, and walk the deck.

   Check: no soft spots. Replace any sheet that flexes, and fasten loose sheathing to the rafters.

2. Lay underlayment from the eave up, each course lapping the one below. IRC R905.10.5 sends metal panels to the same underlayment rules, R905.1.1, as shingles, and Fabral calls for felt or underlayment on any solid deck.

   Check: every lap sheds water downhill, and nothing is wrinkled enough to telegraph through thin steel.

3. Install the eave trim first. Midwest's guide puts eave trim on before the steel, and Fabral says to flash from the bottom up so upper pieces lap over lower ones, with trim laps of at least 6 in set in sealant.

   Check: the trim runs straight along a chalk line.

4. Set inside closure strips on the eave trim, where the first panels will land. They fill the ribs so wind, snow and insects can't get under the panel.

   Check: the closures line up with the panel ribs without being stretched.

5. Square the layout. Measure the two diagonals of the roof plane; Midwest's test is that they match. If they don't, run the panels true to the eave, which is where the eye catches a stepped edge.

   Check: a chalk line snapped perpendicular to the eave for the first panel's edge.

6. Place the first panel at the end away from the prevailing wind, as Fabral recommends, so the laps face away from driven rain. Midwest sets it 1/4 in in from the rake, with 3/4 in to 3 in hanging past the eave. Screw the top and bottom in the flat next to each rib.

   Check: the panel edge sits on the chalk line and the overhang is the same at both ends.

7. Lap the next panel over the first, flush at the eave, and fasten the lap from top to bottom, which Midwest says is what seats the lap and stops capillary leaks. Then fill in the field screws on the pattern: every 24 in up the panel, 9 in apart across it.

   Check: each washer is compressed flat against the steel, the way Fabral describes it. A washer you can spin is too loose; one that is split or dishes the steel is too tight, and Midwest notes that over-torquing also cuts the screw's holding power. Keep off the panels until they are fastened, per Fabral.

8. Every few panels, measure from the last panel's leading edge back to the rake at the eave and at the ridge.

   Check: the two numbers match. A difference means the panels are fanning, and it only gets worse.

9. Install the rake trim over the panel edges from the eave up, each piece lapping the one below. Fabral fastens trim and panel together every 12 to 24 in along the gable.

   Check: the trim covers the cut edge of the last panel and its laps face downhill.

10. Set outside closures on the panels at the ridge, then the ridge cap, lapped 6 in with sealant, screwed through into the ribs or per the trim maker's detail.

    Check: from inside the garage, no daylight shows along the ridge.

11. Sweep every panel and trim piece. Fabral warns that drill filings left on the paint rust and stain it.

    Check: a soft brush over the roof and gutters picks up nothing.

How to install a rolled roof on a low-slope shed

Mineral-surfaced roll roofing covers a shed or porch roof too flat for shingles. The code floor is 1/12 (IRC R905.5.2), and the code also requires installing it per the maker's instructions (R905.5.5). Tarco's instructions for its fiberglass roll roofing are stricter: not on slopes less than 2 in per foot, and only at 50°F or warmer so the laps bond.

The declared shed: 10 ft by 12 ft, a single slope at 2/12, 6 in overhangs. The calculator gives a plan of 13 ft by 11 ft, 143 sq ft, and a roof surface of 145.0 sq ft. The slope from eave to high edge is 11.15 ft, 133.8 in. A 36 in roll laid with 2 in side laps covers 36 in with the first course and 34 in with each after, so four courses of 13 ft reach the top. A 36 ft roll yields two 13 ft pieces, so the shed takes two rolls.

1. Unroll each roll and let it relax in the sun, then cut it into lengths; Tarco suggests 12 ft to 18 ft pieces.

   Check: the sheet lies flat with no waves.

2. Lay the first course full width along the eave, edges flush with the eave and rakes. Nail two staggered rows 18 in on center, 12 in in from each edge, and a row 9 in on center in the lap area.

   Check: every nail will be covered by the next course.

3. Spread lap cement in a thin, even coat over the full width of the lap (Tarco calls for cement meeting ASTM D3019 and warns that too much blisters the sheet), set the next course with at least a 2 in side lap, and roll it.

   Check: a small bead of cement shows along the lower edge of the upper course.

4. If a course needs an end joint, lap it at least 4 in and stagger end laps at least 3 ft from course to course.

   Check: no nail head is exposed anywhere; Tarco says to cover any that are with roof cement.

Mistakes that cost money

Ordering panel length from the plan instead of the slope is the expensive one. The garage's run with overhang is 13 ft; the slope is 13.70 ft. Order 13 ft panels and every one is 8.4 in short at the eave. Ask the store about returns on cut-to-length steel before you order; if it won't take them back, that is $1,221.25 of panels.

Driving panel screws with an impact driver strips them or splits the washer, and a leaking screw on an exposed-fastener roof shows up as a stain months later. One replacement box of screws is $47.98; finding every bad one is the real cost.

Cutting with an abrasive blade burns the edge coating and throws hot filings that, per Fabral, leave rust at the cut and rust marks on the paint of panels you bought for a 40-year finish.

Going over two layers of shingles violates R908.3.1.1. An inspector who catches it sends you back to a full tear-off, with twice the disposal tonnage of one layer.

How much does it cost to install a metal roof? DIY or hire

Roofing contractors, by the 2022 Economic Census figures worked out in the roof replacement cost guide, spend $0.645 on field labor for every $1.00 of materials, then carry overhead and profit of 60.3% on direct cost. Applied to this garage:

The BLS put the national mean roofer wage at $27.95 an hour in May 2025, and construction employers pay $1.438 in total compensation per dollar of wages, $40.20 an hour. The $1,429.30 of field labor is 35.6 hours of a roofer's time. The same comparison for the shed comes to about $738 hired against $279.75 in materials, 4.5 roofer hours.

Done yourself, the garage costs $2,555.95, or $2,670.94 with a new fall protection kit. Even after buying the kit you save $3,626.97, about $102 for each hour a professional crew would have spent. You will spend more hours than that crew, and the fall risk and any bad lap are yours. On a one-story garage at 4/12, do it yourself. On a two-story house or a steep roof, hire the roofer.

To size your own roof, run the footprint, overhang and pitch through the roofing calculator, or measure it by hand with the guide on measuring a roof. If the old roof is leaking now and the metal is weeks away, the roof leak repair guide covers the stopgap.