A Corrugated Metal Ceiling: What the Barn Photo Doesn't Show

A corrugated metal ceiling is an older idea than the farmhouse reference photo suggests. Corrugated iron went up over rooms in houses, churches and railway stations before pressed-metal panels arrived, and it is the documented predecessor of the pressed tin ceiling rather than a modern borrowing from the barn. What the photo leaves out is what happens after the panels are fixed, in a room you sit under, clean and light every day. What "corrugated metal ceiling" actually covers Corrugated is a category, not a single profile. Panel makers sell box-rib and other angular shapes under the same corrugated heading as the classic rounded wave, and rib depth and pitch vary widely across a line, fine pitches included, some marketed for interior ceilings. Two panels described in identical words can read very differently overhead. Thickness is where the shopping gets slippery. A number like 29 gauge is not a guaranteed measurement: gauge is a legacy scale derived from weight, and the same number covers a tolerance band that shifts with whoever rolled the steel. ASTM calls gauge numbers an archaic term of limited usefulness, and the Metal Construction Association advises specifying thickness in decimal inches, which is why spec sheets now print a decimal minimum beside the gauge number. Compare the decimals. That is a steel convention; aluminum is specified in decimals from the start. The ceiling behind the ceiling does most of the work Manufacturers who publish corrugated installation guidance converge on one point: the substructure shows. One warns that framing and decking abnormalities will be transferred to the new metal if not corrected before sheeting begins, and overdriven fasteners get named separately as a cause of oil canning across the face. That language is written for roofs, and the same guides are careful to say that other contributors sit outside anyone's control, stress in the coil, gauge and thermal movement among them, and that mild waviness is inherent to light gauge metal rather than a defect. The prep lesson still carries indoors: get the plane sound, smooth and flat, with existing fastener heads flush, which usually means shimming furring until it reads level before the first panel goes up. Fastening is less settled than the forums suggest. There is no general answer to whether screws go through the raised corrugation or the flat beside it, and manufacturers publish different patterns for the same panel used as roofing and as siding. One US maker's details for a 7/8 inch corrugated profile call for a 2 inch fastener through the crown on a roof but a 1-1/4 inch one on a wall, since a crown-driven screw spans the void under the corrugation before it reaches framing. Trade guidance generally favors the flat beside the rib on ribbed profiles, where the screw bites sooner. Your own panel maker's diagram governs, and it repays reading before you buy screws. Turn a rib horizontal and it becomes a trough Nobody publishes a dust figure for a corrugated ceiling, so take what follows as geometry rather than data. On a wall or a roof, the channels run downhill and shed. Flat overhead, every channel becomes an upward-facing trough the full length of the sheet. Where panels are direct-fastened, as many exposed-fastener profiles are, rows of screw heads and washers sit in that plane too; a concealed-clip or adhesive install skips that. The useful comparison is commercial. The FDA Food Code asks that ceiling materials in a food establishment be smooth, durable and easily cleanable, and nonabsorbent where moisture is involved. None of that governs a home kitchen. It describes what a surface meant to be wiped down should look like, and smooth is the operative word. Above a stove, those troughs sit where cooking aerosol lands first. The kitchen-film side belongs to the wall, and we covered it in the piece on the corrugated metal backsplash. What a metal plane does to light and sound Bare metallic sheet is close to a mirror, and the trade actually measures it. A New Zealand metal roofing industry technical page publishes 60 degree sheen readings of 20 to 25 percent for new unpainted Zincalume, the zinc-aluminum coating sold elsewhere as Galvalume, against 10 to 15 percent for low-gloss coil-coated paint and effectively zero for textured finishes. Two caveats before you lean on that. The same table puts standard coil-coated paint at 25 to 30 percent, glossier than bare sheet, so gloss alone is not the story: unpainted sheet owes much of its glare to how light its color is, and it weathers down. Those readings describe sunlit roofs at a distance, not ceilings, and plain galvanized is a different coating suppliers generally call the shinier of the two. Indoors, geometry takes over. Each rounded rib behaves like a small cylindrical mirror, so one downlight can smear into a bright streak along the rib instead of a soft pool. Low-gloss and textured finishes measurably cut the sheen, though they are sold mainly to hide oil-canning waviness, reduced glare falling out of the same diffusing effect. Sound gets overstated in both directions. Painted drywall absorbs almost nothing already, published tables putting it near NRC 0.05, and solid unperforated metal panel sits in much the same range, roughly 0.05 to 0.10, so metal over drywall is close to acoustically neutral. The genuine downgrade is covering mineral fiber acoustic tile, common in finished basements and usually rated somewhere around NRC 0.50 to 0.70, because anything hard gives that absorption up. Perforated metal backed with an acoustic pad is a different product again, rating 0.70 and above, so "metal ceiling" alone tells you little. On expansion noise, a metal roofing manufacturer says plainly that no installation practice completely eliminates the popping, but those movement figures come from long roof panels in full sun; a conditioned room sees a fraction of that swing over far shorter runs. Where the last panel lands Layout logic is the real difference between corrugated and the pressed-metal ceilings that followed. The National Park Service's preservation brief on historic metal ceilings describes a deliberate anatomy: a patterned field, then a molding, a filler and a cornice around the perimeter. The border pieces were the clever part, made in a variety of widths precisely so they could compensate for irregular rooms, which avoided cutting the field tiles and compromising the pattern. The out-of-square lives in the border rather than in a half-motif in plain view. It was never absolute. The same brief notes rooms the filler alone could not absorb, says historic crews usually started at one corner rather than dead center, and points out that some field cutting is still needed at light and fan hookups. Modern nail-up instructions are the ones telling you to snap centerlines and work outward. Format decides how much of this you inherit, the argument in panels versus 8x8 tiles. Corrugated is usually run the other way, having inherited its habits from roofing: start at one wall, lay strips across, and rip the leftover fraction into a sliver at the far side. That is convention rather than necessity. You can center the run and split the remainder between both walls, absorb some of it in the side laps, or close the edges with trim. The edge-to-edge default was set on roofs, where an off-balance last strip lands somewhere nobody looks. On a ceiling you sit under, decide where that partial panel goes before anyone drives a screw. Corrugated metal ceiling ideas that survive contact with a room Corrugated earns its place where everything above reads as an asset rather than a problem. A porch ceiling wants weather tolerance more than wiping down. A tall volume lets rib pitch read at the distance it was drawn for. In a barn conversion, corrugated steel ceiling panels finish a sentence the building began. When you want the metal itself in a lived-in room, a flat embossed face gives you the material without the trough, the streak or the sliver at the wall. WallWear's Rustic Farmhouse metal tile is real water-resistant aluminum, 8 inches square, ten to a pack covering approximately 4.44 square feet, with the pattern pressed into the face rather than rolled into a rib. Ceilings sit on the brand's own list of intended uses, and installation is peel, stick and trim to fit with a box cutter or scissors: no grout, no special tools, no professional help. Patina Copper reads warmer and aged; Teal and Silver Leaves takes the same relief cooler. Setting out is covered in the metal tile install guide. Frequently Asked Questions Can you use corrugated metal on a ceiling? Yes, and it has a long history indoors: corrugated iron ceilings predate pressed-metal ones. The practical questions are about the room rather than the material. Fix it to a plane that is sound and level, since the substructure telegraphs through, and decide in advance where the partial panel at the far wall lands. How do you attach corrugated metal panels to a ceiling? Through the panel into solid framing or furring, following the profile maker's own fastening diagram. There is no universal rule about screwing through the crown or the flat beside the rib, and manufacturers publish different patterns for the same panel on a roof and a wall. Read the diagram before buying fasteners. Is a corrugated metal ceiling noisy? Over painted drywall the change is small. Drywall absorbs almost nothing already, near NRC 0.05, and solid metal panel sits around 0.05 to 0.10. The real loss comes from covering mineral fiber acoustic tile, usually rated around NRC 0.50 to 0.70, since anything hard gives that absorption up. What is the difference between a corrugated tin ceiling and a pressed tin ceiling? Profile and layout. Corrugated is rolled into repeating ribs and traditionally run wall to wall like roofing. Pressed metal is stamped with a pattern and laid as a field inside a border of moldings and fillers, which absorbs a room's out-of-square so the pattern is not cut. What each is made of varies, as we set out in what "tin" actually means.

Almost nothing sold as a tin backsplash contains any tin. At least six genuinely different materials ship under that one label, and they do not age the same way once they are up on a kitchen wall. Knowing which one you are actually buying is the difference between a finish that stays put and one that starts marking at every cut edge. Six materials sold as a tin backsplash Every result looks like the same product: pressed patterns, aged metallic tones, square panels. Turn the listings over and the specifications scatter. Tin-plated steel. The product with the strongest claim to the name. Steel sheet is stamped with a pattern, then given a thin coating of tin, usually under a powder-coated or sealed color finish. Specialty makers still produce it in two-foot panels. Painted or powder-coated steel. The same stamped steel with no plating at all. The coating is the entire corrosion strategy. Reclaimed and coated barn steel. Sold under the tin name but a different object: a steel sheet whose finish is age rather than a factory coating, cut down from old roofing and wall sheet. Some of it is sold deliberately rusted. PVC and thermoplastic. A large share of what sells under the name. The kitchen consequence is thermal more than visual, because plastic has a service temperature above which it softens and metal effectively does not. Aluminum. A real metal face that is not an iron metal, which changes the corrosion story completely. Copper and stainless. Solid metal instead of a coated sheet, which makes them a different purchase with a different failure mode. Not one of those panels is made of tin. Where tin appears at all it is a thin plating over steel, and often not even that. Why the word stuck to a steel product Federal preservation guidance is unusually direct about this. The National Park Service's brief on historic decorative metal ceilings and walls calls the term a misnomer and records that the sheet steel commonly used for these panels was "neither tin-plated nor galvanized." It also notes that manufacturers and suppliers of the period did not use the term. The Park Service treats the derivation as a matter of debate and offers one possibility: anyone working sheet metal was called a tinsmith, so the work became tin work, and the name outlived the trade. What those panels had instead was paint. Primer cost less than plating or galvanizing, so paint became the corrosion system and not merely the decoration. Which means the historic product was not, as a rule, a self-protecting metal. It was ordinary steel kept dry by a coating, much like the powder-coated panels sold today. One genuine confusion sits alongside this. American tin roofs really were tin-dipped iron, and that is part of why the word survived at all. But the sheet sold for an interior wall was never that product, which is the practical point for anyone shopping now: the name on the listing carries no information about the metal in the box. The kitchen wall was part of the original pitch Pressed metal is remembered as a ceiling material, and the record supports that: walls were the minority application, usually installed alongside a metal ceiling. But the preservation brief is specific that certain patterns were marketed successfully for kitchens and bathrooms, and the reason was hygiene rather than decoration. Painted metal wiped clean where plaster and painted lath did not. Those kitchen patterns are the interesting part. One of the successful ones was a simple grid embossed to imitate the concave grout lines of square ceramic tile, recorded in sheets as large as two feet by eight feet, sold that way for ease of installation and to keep the number of seams down. White gloss stayed the preferred finish wherever sanitation mattered. That description should sound familiar. It is a tile-look metal panel, sold on wipe-clean practicality, in large sheets to minimize joints. A tin backsplash in the kitchen carries on a working idea, not only a decorative one. “Tin” is a pattern name, and the pattern is what you are buying When you shop for tin backsplash tiles, you are almost never specifying an element from the periodic table. You are asking for a particular visual vocabulary: a raised field against a recessed ground, interlocking circles, rosettes and fleurs, beaded borders framing each square, and a relief low enough to read as pattern instead of texture. That vocabulary is the product. The metal underneath is a separate decision, and it decides how the wall ages. The cut edge is where these materials stop behaving alike Every backsplash gets cut. Outlets and switches interrupt the field, and the last column almost never lands on a whole tile. Each of those cuts opens the inside of the material to the room. On tin-plated steel that opening causes a genuine and counterintuitive problem. Tin resists corrosion better than the steel beneath it, and in ordinary damp air that is precisely the trouble. Cut through the plating and you leave a small patch of bare steel ringed by a large area of tin. The two metals in contact behave as a circuit, corrosion concentrates on the bare patch, and it rusts faster than it would have if the tin were not there at all. The plating does not give itself up to protect the cut. (The relationship does flip inside a sealed, oxygen-free, acidic food can, which is why tin cans work, and a kitchen wall is neither sealed nor oxygen-free.) So a cut edge on a steel-cored panel is not finished when it is cut. It is an ongoing obligation you buy along with the panel. Galvanizing behaves the opposite way. Zinc corrodes more readily than iron, so at a scratch or a cut it gives itself up first and the exposed steel is protected. That protection reaches only a short distance across the bare metal, and how far depends on the coating and the conditions, so it covers narrow breaks and not wide patches. Aluminum sidesteps the question. Rust is iron oxide, so an aluminum face does not rust the way steel does; it forms a thin surface oxide instead of a flaking scale, and a freshly cut edge forms one straight away. That is a property of the metal rather than a guarantee about any particular panel or the finish on it. Aluminum's weak point in a kitchen is chemistry: its protective oxide is dissolved by strong alkalis, so caustic degreasers and oven-cleaner-type products are the ones to keep off a finished metal wall. Warm water and a mild, pH-neutral cleaner do the everyday work; our guide to cleaning a metal backsplash covers the rest. PVC cannot rust or corrode, because it is plastic, and in a damp corner that is a real advantage. What it does instead is soften and warp with heat, and the metallic look is a printed layer that can scuff or yellow in a way no amount of buffing will bring back. We have written separately on how to tell real metal from the printed look-alikes. Where real aluminum sits in this vocabulary Our tiles take that pattern language and put it on aluminum. Each pack holds ten embossed tiles at 8" x 8", covering approximately 4.44 square feet, in water-resistant aluminum. The relief is pressed into the metal, never printed onto a film, which is why it keeps changing as the light moves across the wall through the day. Three of the patterns answer the tin request directly: Patina Copper, Rustic Farmhouse and Silver Fleur all carry the raised-field relief the word is actually pointing at. Cutting is the part that matters to this article. WallWear states the install needs no grout, no special tools, and no professional help required; you trim to fit with a box cutter or scissors, nothing you would rent by the day. Because the sheet is aluminum, that fresh edge does not become a maintenance item the way a cut through tin plating does. The full method is in our guide to installing peel and stick metal tile. Two boundaries, stated plainly. The aluminum is water-resistant, which suits the splash zone behind a counter or a vanity without turning the wall into a wet area; showers and standing water sit outside what these tiles are intended for. And near a cooktop we recommend keeping at least 10 inches between the tile and the stovetop, alongside whatever clearance your range manufacturer specifies. Frequently Asked Questions Is a tin backsplash actually made of tin? Essentially never. Tin has only ever been a thin coating over steel, not the sheet itself, and much of what sells under the name today is powder-coated steel, PVC, aluminum or copper. The sheet steel commonly used for historic pressed-metal panels was, in the Park Service's words, neither tin-plated nor galvanized. The word describes a look, not a material. Does a tin backsplash rust? It depends entirely on what sits under the finish. Anything built on steel can rust once the coating is breached, and cut edges around outlets are the usual starting point, which is why sealing them is standard advice. Aluminum does not rust, because rust is iron oxide and aluminum is not an iron metal; it forms a surface oxide instead. Plastic panels do not rust either. Can you use tin ceiling tiles as a backsplash? Sometimes, but check the format before you buy. A lay-in grid tile has no wall equivalent at all, and traditional nail-up panels want a nailable substrate such as sheathing or furring, which is a real construction job instead of a weekend backsplash. Smaller adhesive tiles are made for both planes: ours list kitchen backsplashes, bathroom walls and ceilings among their uses. What is the difference between tin and a pressed tin backsplash? They answer different questions. “Tin” describes the finished look; “pressed” describes how the relief got there, stamped between dies so the pattern is formed in the metal itself. Neither word tells you what the sheet is made of, which is the only thing that changes how the wall ages. We separate the terms in pressed, stamped and embossed.

Buying a house with a pressed-metal ceiling is a different problem from wanting one. The pattern is already up there, some of it painted shut, a corner of it perhaps stained the color of weak tea. An old tin ceiling gives you three ways forward, and they are not equally reversible. Handled well, it is the most valuable surface in the room. Handled quickly, it becomes a plane of dented steel nobody can put back. So the order matters: figure out what you have, read the damage, then choose. Start by identifying what you actually have Three unrelated ceilings get filed under the same phrase, old ceiling tiles. The National Park Service opens its guidance on decorative metal ceilings by noting that the material reads as decorative plaster without being prone to cracking, and lists the metal failure modes separately: water and rust stains, peeling paint, flaking, pitting and holes. A map of fine cracks overhead is plaster, which crazes and bulges between the lath lines. Rust bleeding through paint cannot be anything but metal. The third is a mid-century mineral or fiber acoustical tile, often 12 inches square and stapled or glued to furring, or a larger panel dropped into a suspended grid. Tile of that era, its backing and the adhesive behind it can contain asbestos, and asbestos cannot be identified by appearance, size, pattern or age. Only a laboratory identifies it. Until an accredited inspector has sampled and tested it, do not cut, drill, sand, scrape, break or remove it, and do not drive fasteners through it for furring, track or a grid. Nothing below applies to that material. If you have metal, one piece of vocabulary changes how you treat the ceiling. Tin is a misnomer: the Park Service states that the sheet steel used for these ceilings was neither tin-plated nor galvanized, and that period manufacturers did not use the term at all. No sacrificial coating is protecting it. The paint film is the corrosion protection, which is why stripping it is a bigger decision than it looks. What the magnet test can and cannot tell you A magnet proves the substrate is ferrous. That is all. It cannot separate a 1905 steel ceiling from a modern reproduction, and plaster of that period was sometimes applied over expanded metal lath, so treat a positive result as one input, not a verdict. Better evidence is close up: small nail heads at roughly six-inch centers along a lap line are the signature of an authentic nail-up ceiling, though their absence proves nothing, since some patterns interlocked and were nailed on two sides only. What the rust is telling you Rust is the symptom. Water is the diagnosis. Deterioration here is overwhelmingly water-driven, from exterior leaks, pipes overhead, humidity or condensation, and preservation guidance puts eliminating the source ahead of all cleaning and repair. Fixing the ceiling before you fix the leak buys you a repeat. Water damage usually shows from below, as staining, peeling paint, flaking and pitting. But thick paint can also conceal rusting from behind that has already thinned the metal or opened pin holes, and there was never much to lose: gauge varied by maker, with one 1911 manufacturer working in 28 to 29 gauge mild steel. Get close enough to look properly, and kill the circuits first. Ceiling lights and receptacles usually sit on separate breakers, so switching off one is not enough, and a non-contact tester at the fixture boxes confirms the ceiling is dead. Pressed steel conducts, and cloth-insulated or knob-and-tube wiring often lies against the back of these ceilings. A sag is frequently not a metal problem at all. Where installers laid metal straight over failing plaster without a proper lath grid, the weight of that plaster bears down on the panels, and corroded nails or degraded lathing produce the same drooping edge. The ceiling is a finish, typically hung on wood lath nailed to joists, so a sag is a host-system problem rather than fatigue in the metal. Treat it as structural and as urgent: those panels may be the only thing still holding failed plaster overhead. Do not probe it, pull a panel or try to bring it down. Keep the room clear and have a structural engineer or licensed contractor assess it first. Restoring an old tin ceiling: what it actually involves Start with the reassuring part. Paint build-up alone is not a reason to strip: preservation guidance is explicit that softened lines and some loss of detail do not justify paint removal, and most ceilings can simply be cleaned and repainted. Mild dish soap in warm water, applied with a wet rag and wiped dry, is the recommended starting point, tested somewhere inconspicuous first. Settle the paint question before touching anything. In a building put up before 1978, assume the paint contains lead until a test says otherwise, and note that steel wool, crocus cloth and a scraper disturb it the same way a sander does, directly above your face. Test it, and if it comes back positive the work belongs to a lead-safe certified contractor. Where the paint is confirmed clear, localized rust needs only a spot repair: take the paint back to bare metal in that area alone, lift surface rust with fine steel wool or crocus cloth, feather the edges, then prime with a rust-inhibiting metal primer. Old water stains need a stain-blocking primer instead, a different product doing a different job. Primer choice is where restoration advice most often goes wrong. Writing about new replacement metal, the Park Service says water-based primers generally should not be used, particularly on tin-plated steel, steel, galvanized steel, copper and zinc. This Old House gives the same rule for new panels: clean bare metal with denatured alcohol, prime with an oil-based rust-inhibiting primer, then topcoat in oil or latex. On an old ceiling that applies wherever you have gone back to bare metal, and it applies to the primer, not the topcoat. Which leaves in-place stripping, and it is punishing. High-pressure water systems are ruled out for pressed metal, dry abrasives will most likely damage it, and chemical peels leave a solvent paste on the ceiling for up to 24 hours before it is scraped down over your head. A 500-square-foot ceiling runs to dozens of plates, every one stripped, scraped and rinsed overhead. On pre-1978 paint those scrapings are lead waste with disposal rules attached, which is where most people hand the job to a lead-safe certified contractor; our guide to painting tin ceiling tiles carries the containment detail. Whichever route you take, overhead work has a baseline: sealed eye protection, gloves, and a stable platform. Covering it, and the surface rule that decides everything There are four standard ways to cover an existing ceiling: furring strips with new drywall, a plywood or OSB underlayment carrying new panels, a surface-mount track system, or a suspended grid. All four carry their load mechanically, through fasteners into the joists. That new surface is the structure, and anything applied to its face afterwards, whether paint, wallpaper or adhesive tile, is a finish holding only its own weight. That matters, because adhesive products need four conditions together, not one: clean, dry, flat, and smooth. An embossed ceiling permanently fails the last two, and it fails them geometrically rather than for want of preparation. Historic field patterns carry roughly three-eighths to three-quarters of an inch of stamped relief, and that relief is the panel, not a coating you can scrape flat. Popcorn texture comes off; pressed metal has no equivalent move. Glue-up instructions warn that textured surfaces produce adhesive failure, and gypsum board standards require temporary bracing on adhesive ceiling work until the bond develops. Our own position follows from that. WallWear tiles are peel-and-stick aluminum, and our guidance is that they work on most smooth surfaces. An old pressed ceiling is not one. They fit a covering plan once the flat surface exists: with drywall up over the original, you have a smooth plane, and the pressed language returns without a nail-up install. A 10-pack of 8-inch tiles covers approximately 4.44 square feet, and our guide to installing tin ceiling tiles covers laying the grid out overhead. Replacing it: when the ceiling has to come down Fire code is the constraint most articles skip. Pressed-metal ceilings generally fail current fire resistance requirements: on furring strips over wood joists the assembly rates around 30 minutes, and over intact plaster it may reach an hour. Reaching one hour usually means taking the panels down and reinstalling them over 5/8-inch Type X gypsum board, which is how many rehabilitations get their original ceilings back up. Treat those figures as illustrative, since fire resistance belongs to a specific tested assembly and what your building needs is a question for your building department. Either way it is a reason panels come down, not a reason to discard them. Where pieces are missing, salvage from elsewhere in the building comes first, then patterns still in production. When damage is widespread, recreating the look with new material is a legitimate route rather than a consolation prize. Our tiles are aluminum, worth saying plainly in an article about rust: aluminum does not rust, and the aged character in Patina Copper is a finish rather than oxidation working on the metal. Water-resistant is not the same as immune, so the leak still has to be fixed before anything new goes up. Rustic Farmhouse sets gold ornamental detail against a soft green ground, a more vintage and less metallic read, and Silver Fleur keeps its fleur-de-lis relief crisp in polished silver. It is worth reading what the metal underneath changes first, and if you want the salvaged look specifically, our guide to vintage and antique tin ceiling tiles covers achieving it with new material. Which option fits your ceiling Restore when the metal is sound, the water is fixed and the damage is localized: that is the common case, and the work is mostly cleaning, spot-priming and painting. Cover when the pattern is too far gone to enjoy but the assembly is stable. Replace when rust is widespread, though where lath or fasteners are failing that call belongs to whoever assessed the ceiling. Then rank the three by what can be undone. Repainting can be redone by the next owner, drywall hides the original and leaves it intact behind, and throwing panels away is the only one you cannot reverse. Whichever you choose, fix the leak first. Frequently Asked Questions Is an old tin ceiling worth saving? Usually, yes. Preservation guidance treats decorative metal ceilings as highly durable indoors, and paint build-up alone does not justify removal. The question is not how the ceiling looks but whether the metal is sound and the water is fixed. A stained ceiling over intact steel is a repaint. A rusted-through one over failing lath is not. Can you put peel and stick tiles over an old tin ceiling? Not directly. Adhesive tile needs a surface that is clean, dry, flat, and smooth, and an embossed ceiling fails the last two permanently, because the relief is the panel rather than a coating you can remove. Our tiles are made for ceilings, but like any peel-and-stick product they need a smooth plane to bond to. Put up a flat substrate such as drywall first, then tile that. How can you tell if a tin ceiling is original or a reproduction? Not by pattern, and not reliably by magnet. Historic patterns are still in production, some on period equipment, and a magnet only confirms a ferrous substrate, which plaster over metal lath can also provide. Look instead for small nail heads at roughly six-inch centers along overlapping seams. Modern systems announce themselves through visible T-bar grids or adhesive-and-rivet fixing. What causes rust on a tin ceiling? Water, in nearly every case: a roof or exterior leak, a pipe above the ceiling, persistent humidity, or condensation on cold surfaces overhead. Because these panels are plain steel rather than a coated product, the paint film is the protection, and once it fails the metal can corrode from the upper side, out of sight, before much shows below. Find the water before repainting.