A metal roof will forgive a lot of things. Underlayment is not one of them. I have seen beautifully detailed panels fail early because the layer you never see was chosen poorly or installed in a hurry. I have also seen twenty-five-year-old roofs opened for an addition, and the underlayment beneath was still doing its job, dry and intact. If you are planning a new metal roof installation, the underlayment decision deserves the same attention you give the panel profile and color.
This is the quiet part of the system that handles condensation, stops wind-driven rain, manages heat, and acts as a last line of defense when fasteners loosen or sealant ages. The right product depends on climate, roof geometry, panel type, and budget. The wrong product shows up later as decking rot, rust lines on the underside of panels, or stained drywall after a sideways storm.
What underlayment does under metal
Underlayment is the secondary water-shedding layer between the roof deck and the metal. It must handle three realities that are baked into residential metal roofing and commercial metal roofing alike.
First, metal sweats. Warm moist air from the house meets a cold panel in winter, or the panel cools fast after a summer rain. Micro-condensation forms beneath. Without a layer that can tolerate and redirect that moisture, droplets run to low points, find nail penetrations, and feed decay in the sheathing.
Second, wind drives rain uphill. Even on a roof with perfect lap tension, hurricanes, derechos, and mountain gusts can push water back under ribs and flashings. An adhered, watertight membrane gives the system time to recover without leaks telegraphing indoors.
Third, buildings move. Rafters expand, panels expand more, fasteners loosen a little with thermal cycling. Underlayment must survive this motion without tearing, especially at fasteners and valleys.
When a metal roofing company engineers an assembly, the underlayment choice is not just moisture control. It is temperature tolerance, UV exposure during the construction phase, and compatibility with the panels and the substrate. If you hire metal roofing contractors who treat it as an afterthought, you inherit their risk.
The main families of underlayment
There are four broad categories used under metal today, plus a niche material that deserves mention. Each has a place.
Asphalt-saturated felt remains the old standby. It is the lightest-duty option most homeowners know as 15-pound or 30-pound felt. Real-world weight varies by brand, but the principle is the same: cellulose or fiberglass mat saturated with asphalt. Felt resists initial wetting and works under shingle systems. Under metal, it is serviceable for low-budget installs in mild climates on simple pitches. It tears more easily, wrinkles with moisture, and cannot tolerate prolonged heat under dark panels on low-vented attics. In high-UV or high-heat markets it ages quickly during construction if panels lag, and it often telegraphs its wrinkles into the panel plane.
Synthetic underlayment covers a range of spun-bond or woven polyolefin sheets. Think Tyvek-like material for the roof deck, generally installed with cap nails or screws. Synthetics resist tearing, can sit exposed for weeks without breaking down, and lie flatter than felt. Quality varies widely. Thin economy rolls feel like tarps and slide under foot. Premium synthetics have robust anti-slip surfaces and tested temperature ratings. Under metal roofing installation, synthetics are the most common choice for budget-conscious projects that still want better holdout and safety than felt.
Peel-and-stick ice and water shield, formally self-adhered bituminous membrane, is the workhorse for eaves, valleys, hips, and penetrations. Many crews use it as full-deck coverage under standing seam and mechanically seamed metal. The adhesion locks the membrane to the deck, closing off nail penetrations and resisting wind-driven water. The better products have high-temperature ratings, often 240 to 260 degrees Fahrenheit, and release films that make installation cleaner. Under metal, high-temp matters. Standard ice shield can soften under dark panels in summer and bleed asphalt, bonding to the back of panels or dripping tar-like residue. That is a warranty headache you can avoid.
High-temperature underlayment is a label applied to both self-adhered and synthetic products engineered for the heat under metal and tile. Verify the max in-service temperature and read the fine print. I have pulled off panels to find beautiful membranes failed because they were only rated to 180 degrees. On a black standing seam roof in a southern exposure, deck temps can cross 200 degrees. A high-temp self-adhered membrane paired with clip-fastened standing seam has become a standard in premium residential metal roofing and many commercial metal roofing jobs where the assembly is expected to last decades with low maintenance.
Felt-backed or condensation-control membranes are a niche but growing category. Some are thin non-woven pads that allow micro-condensate to form and evaporate without dripping. They are used either as underlayment or bonded to the panel underside. In metal buildings and open framing where there is no deck, these products are helpful in controlling the morning rain indoors effect. On fully decked roofs in homes, they can add a margin of safety in high humidity zones if you pair them with proper ventilation.
Climate and code steer the decision
Local code sets the floor, not the ceiling. Eave ice dam protection in cold climates usually requires at least 24 inches inside the warm wall or a set distance from the edge. Wildland urban interface zones sometimes require class A assemblies, which affects underlayment options. Coastal high-wind counties may specify nail spacing, cap fasteners, or require self-adhered membranes at the perimeter.
Beyond code, climate narrows the field. In snow country with interior humidity, condensation risk is real. A high-temp self-adhered membrane from eaves to at least 24 inches upslope of the interior wall line handles ice dams, then continue with either the same product or a high-grade synthetic up to the ridge. On shallow pitches, valley areas, and dead valleys created by dormers, I favor full self-adhered coverage because wind and water conspire there.
In hurricane and tornado regions, peel-and-stick from eaves to ridge makes sense, especially on complex roofs with many hips and dormers that invite wind-driven water. The sealed deck acts as a continuous barrier if the metal skin is damaged by flying debris then replaced within weeks. That sealed deck saved more than a few structures I inspected after late-season storms on the Gulf Coast.
Hot arid climates teach a different lesson. Felt shrivels. Low-grade synthetics get brittle. High-temp synthetic underlayments excel because they resist baking and provide a safe walking surface for crews on hot days. Self-adhered is still useful at penetrations and valleys, but full coverage is not always necessary if the panel system is seamed tight and the attic ventilation is balanced.
Panel system and roof geometry matter more than most think
A through-fastened panel system, often used on barns and some budget homes, puts hundreds of screws through the panel surface into the deck or purlins. Those fasteners work hard over time. Thermal cycling loosens them incrementally, and washer failure is a common source of drips. Under these systems I prefer a more robust underlayment, usually a high-temp self-adhered membrane in valleys and at full eave-to-ridge coverage on low-slope sections, and at minimum a premium synthetic elsewhere. It buys time and keeps the deck dry when the occasional screw backs out and you do not catch it for a season.
Standing seam, especially mechanically seamed systems on low slopes, can be incredibly watertight at the panel level. Clips allow expansion, and seams are either snapped or crimped. With these, high-temp underlayment still matters, but the choice between full self-adhered coverage and hybrid coverage depends on slope and complexity. On simple gables at 6:12 or steeper, a high-temp synthetic with peel-and-stick at edges, valleys, and penetrations is reliable. On low-slope standing seam at 2:12 to 3:12, I want full self-adhered deck coverage. The margin is worth the cost.
Geometry complicates everything. Big valleys, inside corners where roofs die into walls, long unbroken eaves under tall slopes that concentrate water, and dead-flat transitions all deserve extra attention. I have replaced underlayment in valleys that looked perfect elsewhere. The installer had used a generic ice shield that softened each summer and crept under panel stress, eventually tearing where water rolled over nail heads. Underlayment should be upgraded in these stress areas even if the field gets a different product.
Ventilation and vapor strategy underneath
A roof is a system, not a sandwich. Underlayment alone cannot fight moisture if the attic is a steam bath. Before the first roll goes down, confirm the ventilation strategy matches the insulation strategy. If you have a vented attic, you want clear soffits, a continuous ridge vent or equivalent, and no bath fans dumping into the space. If you have an unvented assembly with spray foam at the roof deck, the underlayment must tolerate the heat load, and the foam must be continuous and thick enough to control dew point at the deck.
Metal roofs amplify mistakes here because they run cooler on clear nights and hotter on direct sun than asphalt shingles. The temperature swings drive moisture movement. I have seen metal roof repair calls that start with “the roof is leaking,” but the problem was condensation from a bath fan venting into the attic, dripping onto the back of the deck, then finding a joint. A well-chosen underlayment will shed that drip for a while, but the fix is ventilation, not more membrane.
Real numbers and expectations
It is helpful to talk in ranges. On a typical 2,200 square-foot roof, materials for premium synthetic underlayment might add 600 to 1,200 dollars more than basic felt. Full-coverage high-temp self-adhered membrane can add 1,500 to 3,000 dollars beyond synthetics, depending on brand and regional pricing. Labor differences are real too. Peel-and-stick installs faster in many hands because you avoid cap-nailing an entire deck, but it requires clean, dry, warm-enough conditions to bond well. In shoulder seasons, I have had crews wait until late morning to start rolling membranes when the deck warms to bonding temperature. That patience pays off.
As a rule, underlayment for metal should be rated to at least 230 degrees Fahrenheit, preferably 250 degrees or higher, especially for dark colors. Verify fire ratings when part of a class A assembly is required. Ask the metal roofing contractors to provide the technical sheets, not just marketing brochures. You are looking for UV exposure limits, temperature rating, nail sealability, and compatibility statements for treated wood if your deck is not standard OSB or plywood.
Common failure patterns I see
Wrinkling and bridging are two. Wrinkled felt, once trapped under a panel, creates air gaps where condensation collects and runs. Bridging with self-adhered membrane happens when installers stretch the sheet over a valley rather than bed it tight into the center. Later, the membrane sags and tears at the fold under load. I insist on a valley roller and a dry-fit before backing off release films.
Another common pattern is underlayment that stops short of the interior warm wall in cold climates. Ice dams do not obey fascia lines. The membrane needs to roll far enough upslope to cover the zone where meltwater freezes and backs up. On cathedral ceilings, that can be half the rafter length during cold snaps.
A third is poor sequencing around penetrations. Plumbers and HVAC techs sometimes cut underlayment to get work done, then do not seal it back. On coordinated projects, the metal roofing company controls the schedule and wraps each pipe or curb with peel-and-stick before the jack or curb goes in. When schedules slip and trades step on each other, the underlayment becomes a patchwork. That shows up as leaks months later, blamed on the metal roofing installation, when the root cause is a slit in the membrane never patched.
When to choose which: practical guidance
- Mild climate, simple 6:12 gable, vented attic, light-colored standing seam: premium synthetic on the field, high-temp self-adhered at eaves, valleys, rakes, and penetrations. Cold climate with ice dam history, 4:12 roof with several valleys: high-temp self-adhered full coverage, especially if choosing through-fastened panels or snap-lock below 4:12. Coastal high-wind zone, complex hip-and-valley roof, dark panels: high-temp self-adhered full deck coverage, plus extra membrane headlaps under ridge and hips, because flying rain will find the oddest paths. Low-slope 2:12 standing seam, cathedral ceiling, unvented assembly with spray foam: high-temp self-adhered full coverage, and confirm foam thickness to control dew point. Here the membrane sees high heat and must tolerate it. Agricultural building with purlins and no deck, condensation concerns, limited budget: use a panel with factory-applied anti-condensate fleece or a condensation-control underlayment over purlins, and consider adding a radiant barrier and controlled ventilation. This is a different animal than decked residential metal roofing.
Working with pros, and what to ask
A good local metal roofing services provider will talk underlayment first, not last. They should be comfortable with more than one brand and able to explain why they prefer a specific product for your roof. If they brush off the question with “we use whatever is on the truck,” keep asking or get a second bid.
Ask for the exact product names, ratings, and exposure limit. Ask how long they expect the underlayment to sit before panels go on. I budget for same-week paneling whenever possible. Underlayment is not a long-term roof, and while high-end synthetics claim four to six months UV exposure, every week uncovered invites dust, trades traffic, and minor damage. On a metal roof replacement where tear-off and dry-in happen ahead of a storm, a sealed deck with high-temp self-adhered membrane is cheap insurance.
Metal roofing repair service calls often reveal the quality of the original underlayment work. If a contractor dismisses failures as “just metal roofs,” find someone else. Metal roofs perform exceptionally when installed as a system. Underlayment is part of that system, and good crews treat it that way.
Installation details that separate good from average
On decks with knots or rough OSB, a quick broom pass makes a big difference in adhesion for peel-and-stick membranes. I keep https://metalroofingcompanymiami.com/ a magnesium float handy to knock down proud sheathing joints. Ridge lines get a double course of self-adhered membrane in high-snow regions where drifting occurs, even if a ridge vent will be cut later. Valleys get a 36-inch strip centered before the field membrane laps over, not after. Sequence matters.
Cap fasteners on synthetics are not optional under metal just because the panels cover them. Ring-shank nails with plastic caps hold the sheet flat and resist wind uplift during the build, which in turn keeps panels flat. Staples telegraph into bumps and create hand-slap noises under panels when the wind blows, a complaint I have heard more than once on otherwise well-built roofs.
At eaves, I like to run self-adhered membrane onto the fascia by 1 inch under the drip edge, then run a second strip of the same over the drip edge lip onto the field membrane. It creates a belt-and-suspenders seal so that wind-driven water cannot wick behind the metal edge. On rakes, a 6-inch peel-and-stick strip beneath the rake trim is cheap protection where sideways rain tends to test the system.
Warranty interactions and manufacturer specs
Panel manufacturers publish underlayment requirements in their installation manuals. They vary. Some require high-temp self-adhered under any standing seam to maintain paint finish warranties. Others allow synthetics with peel-and-stick at details. Pay attention to language about compatibility with copper, zinc, or bare steel. Bituminous adhesives can react with certain metals over time. If you are installing a specialty metal like zinc, the underlayment choice narrows further, and the system will likely include a vented batten or separation layer.
A metal roof installation should come with two distinct warranties: the paint and panel warranty from the manufacturer, and the workmanship warranty from the contractor. Underlayment choices affect both. If a crew substitutes a lower-temp membrane than specified and heat damages paint from the underside, you can find yourself in a finger-pointing match. Keep invoices and spec sheets in your project file. Transparency helps.
Cost trade-offs through the lens of risk
I have never had a client call me years later to complain they spent too much on underlayment, but I have fielded many calls to ask how a stain ended up on their ceiling after a spring storm. When you amortize the cost difference over 30 to 50 years, a better membrane is a rounding error. On a 20,000 dollar roof, the jump from mid-grade synthetic to high-temp self-adhered full coverage is often 8 to 12 percent, sometimes less when labor efficiencies balance material cost.
Risk sits in geometry and climate. A simple ranch in a moderate climate on a hill with clean airflow can carry a synthetic field with peel-and-stick details confidently. A chopped-up two-story with intersecting roofs beneath tall trees in freeze-thaw country earns the full-dress membrane package. Let risk, not only budget, decide.
How underlayment choices interact with future repairs
Think about metal roofing repair down the road. Through-fastened panels will need periodic screw replacement. A sealed deck beneath turns that maintenance into a dry experience instead of a water-tracking nightmare. If you plan solar, satellite mounts, or future skylights, mark the deck with photos before panels cover it. Knowing where the underlayment laps and how the membrane runs helps a metal roofing repair service avoid cutting in the wrong place years later.
If the roof ever suffers storm damage and needs partial metal roof replacement, a well-adhered underlayment makes temporary dry-ins and sectional panel swaps faster. Crews can pull panels, leave the membrane intact for a night if weather threatens, and come back to finish. I have done it both ways, and a tight self-adhered deck is the difference between a nervous tarp and a calm dinner.
The role of local knowledge
National advice only goes so far. A local metal roofing company that works your microclimate knows the wind patterns and the quirks of local building stock. In one coastal community I serve, afternoon sea breezes turn to night gusts that drive rain under rakes in a very specific quadrant. We run extra peel-and-stick along those rakes as standard. In a mountain valley nearby, snow slides hard in March and piles at the eaves. We protect the first six feet with high-temp self-adhered membrane and specify beefier drip details to resist the shear. Local metal roofing contractors earn their keep on these details.
If you solicit bids, do not only compare panel gauges and colors. Ask each bidder to describe their underlayment plan. The most detailed answer is often the best roof, even if the number is not the lowest. The contractors who talk about sequencing, temperature windows, and membrane transitions are the ones who will solve small problems on the deck before they become big problems in your living room.
Final thoughts from the field
Underlayment choices are not glamorous. You will never see them again after installation day. They will not help sell your house with curb appeal. They will, however, keep your sheathing dry when a fastener breaks, quiet the tick of thermal movement, and buy you time in the chaos after a storm. For new metal roof installation on homes or commercial buildings, treat underlayment as the quiet professional in the crew. Let it do its job with the right materials, careful install, and climate-aware planning.
If you are weighing options right now, put your money where it matters. Choose high-temp rated products beneath dark panels and low-slope sections. Use self-adhered membranes generously at edges, valleys, and complex intersections. Buy enough quality synthetic to keep the field tight where peel-and-stick is not necessary. Pair all of it with a ventilation plan that suits your insulation strategy. Then hire a team that cares about what happens before the metal shows up on site. That is how metal roofing services deliver roofs that last as long as reputation implies.
Metal Roofing – Frequently Asked Questions
What is the biggest problem with metal roofs?
The most common problems with metal roofs include potential denting from hail or heavy impact, noise during rain without proper insulation, and higher upfront costs compared to asphalt shingles. However, when properly installed, metal roofs are highly durable and resistant to many common roofing issues.
Is it cheaper to do a metal roof or shingles?
Asphalt shingles are usually cheaper upfront, while metal roofs cost more to install. However, metal roofing lasts much longer (40–70 years) and requires less maintenance, making it more cost-effective in the long run compared to shingles, which typically last 15–25 years.
How much does a 2000 sq ft metal roof cost?
The cost of a 2000 sq ft metal roof can range from $10,000 to $34,000 depending on the type of metal (steel, aluminum, copper), the style (standing seam, corrugated), labor, and local pricing. On average, homeowners spend about $15,000–$25,000 for a 2000 sq ft metal roof installation.
How much is 1000 sq ft of metal roofing?
A 1000 sq ft metal roof typically costs between $5,000 and $17,000 installed, depending on materials and labor. Basic corrugated steel panels are more affordable, while standing seam and specialty metals like copper or zinc can significantly increase the price.
Do metal roofs leak more than shingles?
When installed correctly, metal roofs are less likely to leak than shingles. Their large panels and fewer seams create a stronger barrier against water. Most leaks in metal roofing occur due to poor installation, incorrect fasteners, or lack of maintenance around penetrations like chimneys and skylights.
How many years will a metal roof last?
A properly installed and maintained metal roof can last 40–70 years, and premium metals like copper or zinc can last over 100 years. This far outperforms asphalt shingles, which typically need replacement every 15–25 years.
Does a metal roof lower your insurance?
Yes, many insurance companies offer discounts for metal roofs because they are more resistant to fire, wind, and hail damage. The amount of savings depends on the insurer and location, but discounts of 5%–20% are common for homes with metal roofing.
Can you put metal roofing directly on shingles?
In many cases, yes — metal roofing can be installed directly over asphalt shingles if local codes allow. This saves on tear-off costs and reduces waste. However, it requires a solid decking and underlayment to prevent moisture issues and to ensure proper installation.
What color metal roof is best?
The best color depends on climate, style, and energy efficiency needs. Light colors like white, beige, or light gray reflect sunlight and reduce cooling costs, making them ideal for hot climates. Dark colors like black, dark gray, or brown enhance curb appeal but may absorb more heat. Ultimately, the best choice balances aesthetics with performance for your region.