Corrugated metal roofing
Corrugated Metal Roofing for New Jersey Garages, Sheds and Barns
Corrugated metal roofing in NJ is the wavy, exposed-fastener panel you know from barns and garden sheds, and it is still a practical roof for outbuildings and porches on residential property. We install it on detached garages, sheds, barns, porch roofs and farm buildings that belong to a home; we do not roof commercial buildings.
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The basics
What is corrugated metal roofing?
It is a sheet of steel or aluminum rolled into repeating waves and held down by screws driven straight through the panel surface. Each panel laps over the next at the sides and, on longer roofs, at the ends.
The screws carry sealing washers that press against the metal to keep water out. That is the key difference from standing seam, where clips under the seams hold the panels and nothing pierces the flat of the panel. Exposed fasteners make corrugated quicker to install and usually less expensive, but they need checking over the years.
Ribbed exposed-fastener panels, with flat sections between taller ribs, work the same way and follow the same rules on this page.
Where it fits
Where does corrugated metal make sense on a residential property?
On buildings where function counts more than a finished look, and where an occasional screw check is easy. Typical fits:
- Detached garages and workshops
- Garden sheds, wood sheds and pool houses
- Barns, stables and run-in sheds on residential farms in Hunterdon, Sussex, Morris and Somerset counties
- Porch, patio and carport roofs
- Chicken coops and small farm buildings
For a home’s primary roof, standing seam is usually the better choice, because its fasteners sit under the seams and its panels can run eave to ridge; see standing seam metal roofs. For a traditional look on the house itself, see metal shingles.
Slope
How flat can a corrugated metal roof be?
Under the model code text, lapped panels without soldered seams need a pitch of at least 3:12; with sealant applied in the laps, the floor drops to 1/2:12 (2024 IRC text, R905.10). The panel maker’s instructions can set a higher minimum, and they govern.
| Roof slope | Lapped panels under the model code text | What to plan |
|---|---|---|
| 3:12 and steeper | Standard laps | Follow the maker’s side and end lap rules |
| 1/2:12 to under 3:12 | Laps sealed with applied lap sealant | Low porch and lean-to roofs often fall here |
| Under 1/2:12 | Not allowed for lapped panels | A standing seam rated for the slope, or another roof type |
Low porch and lean-to roofs are where slope matters most. We measure every roof plane before pricing; if a porch roof is too flat for lapped panels, we price a mechanically seamed standing seam that its maker rates for that slope instead.
Upkeep
How do you maintain the exposed fasteners?
Check the screws once a year and after major storms, and replace any whose washers have cracked, dried out or backed away from the panel. A failed washer is one of the most frequent leak sources on screw-down roofs.
- Screws driven too tight crush the washer; too loose and it never seals. The right depth leaves the washer snug, not squashed flat.
- Panels expand in summer heat and contract in winter cold, and over the years that movement can wallow out screw holes.
- A slightly larger replacement screw can re-seal a worn hole.
- Keep leaves and debris off the panels and out of the laps, where they hold moisture against the metal.
Match the metals, too. The Metal Sales Galvalume warranty leaves out panels touching copper or lead, panels taking drainage off copper or lead flashings or pipes, and harm caused by green or wet lumber touching the steel. That last exclusion matters on barns framed with fresh lumber.
Condensation
How do you stop condensation under a metal roof?
Condensation forms when warm, moist air inside the building meets the cold underside of the panels. The fixes are a layer between the metal and that air, and a way for moist air to leave.
- Solid sheathing with underlayment under the panels, the usual build on garages and finished outbuildings
- A condensation-control fleece on the underside of the panels, which some panel makers offer, where panels go straight over purlins
- Ventilation at the eaves and ridge so moist air leaves instead of collecting under the roof
- For a heated building, insulation and an air and vapor control plan set by its designer
Animals, wet hay, firewood and snow-covered cars all add moisture, so barns and garages often need more than one of these steps.
The state makes an ice barrier mandatory in Sussex County alone, and DCA Bulletin 07-3 exempts detached accessory structures with no conditioned space from that rule. Over a heated or finished outbuilding, we can add the same eave membrane we use on house roofs.
Metal and finish
Steel or aluminum, and which finish?
Galvalume-coated steel, bare or painted, suits most inland outbuildings. Close to salt water, aluminum is the safer pick, since Metal Sales leaves Galvalume roofs closer than 1,500 feet to salt water, or exposed to sea air and spray, out of its warranty.
Paint follows the same logic as on a house. MBCI describes PVDF as its finish for stronger color retention and SMP as its most economical option. On a shed at the back of the lot, SMP is often enough; on a porch roof beside the house, a PVDF color match may be worth the difference.
Permits, cost and warranty
Do outbuilding roofs need a permit, and what do they cost?
The ordinary-maintenance rule that frees a freestanding one- or two-family house from a re-roofing permit is written for the house itself. Garages, barns and new porch roofs follow their own rules, so check with your town’s construction office. Under the state’s home improvement practices rules, no contractor may begin work until every required permit has been issued.
We price outbuilding roofs from a measurement, and the national cost guides we cite publish no separate corrugated figure. Screw-down panels generally cost less to install than standing seam, which HomeGuide lists between $9 and $16 a square foot nationally, because there are no clips or seaming. For what drives any metal roof price, read the cost guide for metal roofs.
For sales tax, a whole new roof counts as a capital improvement, untaxed once the owner fills out Form ST-8 for the contractor; repairs stay taxable (bulletin S&U-3). If the building needs gutters, we can price seamless gutters at the same time.
Warranty
Our written workmanship warranty covers the installation, and the panel and paint makers warrant their products.
Our workmanship warranty is a lifetime warranty: it covers our installation work for as long as you, the homeowner who signs the contract, own the home. It does not transfer to a later owner. Materials and paint finishes carry their manufacturers' own warranties, and the full written warranty comes with every estimate so you can read it before you sign.
Our warranty page explains what each covers and how to make a claim.
Get a free estimate
Or call (732) 231-5327.
Corrugated metal roofing questions
Can corrugated metal go on my house roof?
It can, but standing seam is usually the better choice for a main roof because its fasteners are hidden and its panels can run eave to ridge. Corrugated fits garages, sheds, barns and porch roofs best.
How low a slope can corrugated metal handle?
The model code text lets lapped panels go down to 3:12 with plain laps, or 1/2:12 when the laps are sealed. The panel maker may require more. Below that, a standing seam rated for the slope is the usual answer.
When should I inspect the screws on a corrugated roof?
A yearly look, plus one after any big storm, is a sensible routine. Replace any screw whose washer has cracked or backed out, since a failed washer often lets water in.
Why is my barn or garage roof dripping inside when it is not raining?
That is usually condensation: warm, moist air meeting cold metal. Solid sheathing with underlayment, a condensation-control fleece on the panels and better ventilation are the usual fixes.
Do I need an ice and water membrane under corrugated metal on a shed?
Not by code in most of New Jersey. The ice barrier rule applies only in Sussex County, and DCA Bulletin 07-3 exempts detached accessory structures with no conditioned space.
Do you install corrugated roofing on commercial buildings?
No. We install corrugated metal only on residential property: garages, sheds, barns, porches and farm buildings that belong to a home.
Free estimate
Get a price for your garage, shed or barn roof
Tell us the building and its rough size. We set up a visit, measure every roof plane and write up the price.
Call (732) 231-5327 or send the form. We serve ten counties in central and northern New Jersey; see our service areas.