Materiales · ASTM C1396 · ASTM C840 · GA-216
Casi todos los paneles con cara de papel y los de malla de fibra de vidrio que están abajo se fabrican bajo ASTM C1396; las normas de instalación son ASTM C840 y el GA-216 de la Gypsum Association. La tabla está escrita para que sirva de pie en el pasillo de la tienda.
Nada de esto es una cita de código para tu trabajo. Los ensamblajes con clasificación de resistencia al fuego se rigen por el diseño probado y listado que está en los planos, y las jurisdicciones locales enmiendan el código estatal. Nosotros lo confirmamos con el departamento de edificios que tiene el permiso.
Tipos de panel
Once paneles. Cada fila abre con la corrección o la trampa que trae ese producto — casi todos tienen una, y casi todas cuestan dinero cuando se descubren tarde.
Whiteboard, sheetrock
The default board for non-rated interior walls and ceilings. Gypsum core, paper faces, tapered long edges so the joint has a recess to fill.
1/2 in. is the general-purpose wall board. 3/8 in. shows up in older houses and as a base layer in double-layer work. 1/4 in. is for resurfacing over existing walls and for curved work — radius walls, barrel vaults, arched openings — usually doubled, because it bends to a tighter radius than thicker board. 1/4 in. is not a single-layer finish over open framing.
Fire-rated board
The board used in most fire-resistance-rated wood and steel stud assemblies. Glass fibers are mixed into the core, so as the gypsum calcines in a fire the core holds together longer instead of cracking apart.
The thing most people get wrong: gypsum board has no fire-resistive rating in and of itself. AWCI says exactly that. The rating belongs to an entire tested assembly — stud size and spacing, board type and thickness, orientation, fastener type and spacing, insulation, joint treatment. Change one item and you are outside the listing, and the listing is what the inspector is checking. Type X is what makes a rated assembly possible. It is not the rating.
Proprietary Type X
Enhanced fire performance beyond Type X. Most often specified as the ceiling membrane in rated floor and ceiling assemblies, and in column and beam protection.
The difference is chemistry, not thickness. Type C carries a higher percentage of glass fiber plus vermiculite, which expands at roughly the same temperature the gypsum core is losing its water and trying to shrink, so the two more or less cancel and the board stays the size of the opening instead of pulling away from the framing. The Gypsum Association's rule is worth memorizing: all Type C boards are Type X, but not all Type X boards meet the enhanced requirements of Type C, and using Type X where Type C is required can compromise the rating. Type C is also a special-order item at most yards, so it has to be caught at takeoff, not on hang day.
Green board
Paper-faced board with a water-resistant core and treated face paper, for damp but not wet locations.
Two corrections, one in each direction. It is not a tile substrate in a shower or tub surround — since the 2006 code cycle the codes have required cement backer units, fiber-cement backers, glass-mat gypsum or fiber-reinforced gypsum panels in the wet area instead. But it is also not banned from bathrooms, which is the mistake people make going the other way. Painted bathroom walls and tiled walls outside the wet zone are still fair game. Cut and exposed edges get sealed the way the manufacturer says.
Purple board, paperless board, glass-mat board
Bathrooms, laundry rooms, garages that get washed down, coastal houses with high humidity, and any wall that has flooded before.
Two different families that get confused. Glass-mat faced board has fiberglass mat on both sides instead of paper, so there is no paper for mold to eat. Treated paper-faced board is still paper-faced, with a mold- and moisture-resistant core and treated paper. Either one buys time against humidity and incidental moisture. Neither one is waterproof, and neither one makes a wall waterproof. Behind tile in a shower the waterproofing is a separate membrane, and the board is not a substitute for it.
Corridors, schools, gyms, multifamily common areas, commercial kitchens, and the garage wall where the bikes go.
They are two different things and the labels get used loosely. Abuse resistance is about the surface — scuffs, gouges, a cart scraping a corridor wall. Impact resistance is about the assembly — something hitting the wall hard enough to punch through, which usually means mesh or fiberglass reinforcement in the core. ASTM C1629 classifies both, across surface abrasion, indentation, soft-body impact and hard-body impact, at Levels 1 through 3 with Level 3 highest. Pick by which failure you are actually trying to prevent, because paying for impact where you needed abrasion is common and does nothing.
Sound-damping board
Bedroom and media room walls, home offices, party walls, anywhere one layer has to do the job of two.
These are constrained-layer damping panels: gypsum layers with a viscoelastic polymer between them that turns the bending energy of the panel into heat, so the wall stops behaving like a drumhead. The product most people know by name is made on the West Coast. The honest comparison is against the other approach — two layers of ordinary board with a damping compound between them, which often performs comparably and can cost less in material, but doubles the hanging labor, adds thickness, and is much easier to get wrong. The laminated panel wins on wall thickness, labor and repeatability. Neither approach fixes a flanking path: outlets back to back, a shared duct, a continuous floor. Sealing the perimeter matters more than most people expect.
Liner panel
Shaft walls and area separation walls. Elevator hoistways, stairwells, utility and ventilation shafts, chutes, and the walls between attached units.
One inch thick and twenty-four inches wide, with a heavy noncombustible Type X core. The width is the whole idea: the panel slides into the framing of a shaftwall system from one side, so you can build a rated shaft where there is no back side to work from. Area separation walls between attached dwellings use the same panels in systems designed to release from a collapsing structure and leave the wall standing for the neighbor. Which system and which listing governs is set by the assembly on the plans, not by the panel.
Backer board
Behind tile in showers, tub surrounds and wet areas, and under tile on floors and counters.
Cement board is not waterproof. It is water-durable — it will not rot or lose strength when it gets wet — but water passes straight through it. In a shower the waterproofing is a separate membrane, sheet or liquid-applied, either behind the board or on its face. A shower built on bare cement board with no membrane will fail behind the tile eventually. Foam backer boards with a cement-polymer facing are now common and are waterproof in themselves, which is why a lot of tile setters prefer them; they sit outside the cement-board and gypsum-backer ASTM families and are approved by evaluation report instead, so check the specific product.
Soffits, covered walkways, carports, large canopies, and the sidewalls of protected exterior corridors and breezeways.
The words that matter are indirect exposure. The board is rated for locations protected overhead where the assembly drains and it never sees direct rain or standing water. A soffit under a deep overhang is what this product is for. The underside of a balcony with an open rail, where wind-driven rain blows straight up into it, is not, and it will delaminate. Exterior soffit joints also want a setting-type or exterior-grade compound — a drying-type ready-mix in marine air is asking for trouble.
Interior ceiling board
Ceilings framed up to 24 in. on center, including ceilings that are going to get a hand-applied or water-based texture.
This is a different product from regular 1/2 in. board — a stiffer, denser core engineered not to sag at 24 in. on center under the weight of wet texture or blown insulation. It is the alternative to going up to 5/8 in. on a textured ceiling. Limits worth knowing: interior only, not for exterior soffits, not for continuous-moisture areas like pools and steam rooms, it is nonstructural and is not a nailing base, and there is a cap on how much insulation can be laid over it. Almost every wavy, sagging ceiling in a 1990s or 2000s tract house is regular 1/2 in. board on 24 in. framing that then got sprayed with a water-based texture.
Los espesores de arriba son los que se fabrican para ese producto, no una recomendación para tu pared. En un ensamblaje clasificado el espesor, el tipo de panel, la orientación y la sujeción salen del diseño listado, no del hábito.
La corrección de California
No, and the claim is more common than the requirement. The dwelling-and-garage separation table in the California Residential Code, Table R302.6, calls for not less than 1/2 inch gypsum board applied to the garage side of the separation from the residence and its attics. It calls for 5/8 inch Type X only from habitable rooms above the garage. So a common garage wall, or a garage ceiling with nothing but attic above it, is a 1/2 inch requirement under the state code. That said, most of what we hang here is 5/8 Type X anyway, and for real reasons rather than habit: the great majority of listed one-hour wood and steel stud assemblies specify it, so any rated wall drives it; and a ceiling framed 24 inches on center that is getting a water-based texture needs sag-resistant ceiling board or 5/8, which describes most ceilings in this region. Jurisdictions also amend the state code, so we confirm with the building department that holds the permit instead of assuming either way.
Compuesto para juntas
La diferencia es cómo endurece. El compuesto de secado pierde agua: se puede retrabajar, encoge más y no seca hasta que el cuarto lo deja. El de fraguado endurece por reacción química: fragua con reloj aunque el cuarto esté frío, húmedo o sin aire, encoge muy poco, pega más fuerte, y no se puede retrabajar una vez que arranca.
Se endurece al perder agua. Se puede retrabajar mientras esté húmedo.
Highest shrinkage, strongest bond, hardest to sand of the ready-mix family. You use it where bond under the tape matters more than how easy the sanding is, which is exactly what a bed coat is.
Lowest shrinkage, easiest to apply and easiest to sand. It is not a bedding compound — it does not have the bond for it. The traditional three-bucket system is taping compound for the bed and topping for the coats, and it is still what you use when you want maximum bond underneath and minimum sanding on top.
The practical compromise that dominates day-to-day work. Moderate shrinkage, acceptable bond, acceptable sanding — good at both ends of the job without being best at either. One bucket on the truck instead of two.
Less shrinkage and sands considerably easier than conventional weight, which is why so many crews finish with it. It also has less bond strength than conventional-weight compound, which makes it the wrong choice for a bed coat on a critical job and the wrong choice with mesh tape.
Se endurece por reacción química, con reloj. El número del grado es un tiempo de fraguado nominal, no un tiempo de trabajo.
Mix what you can use and nothing more. A dirty pan or a trace of set compound from the last batch will kick it early, which is why finishers are religious about clean tools.
The grade for a one-day repair where you need three passes before you leave. Knock it down while it is still damp rather than sanding it hard later.
The grade number is a nominal set time, not a working time, and the published ranges are wide — one common 45-minute product lists thirty to eighty minutes, because temperature, water temperature, water cleanliness and humidity all move it.
Longer grades exist above this. The high-strength setting compounds are brutally hard once set and should be smoothed before they set or while still damp; most crews run setting compound for the bed and the fills and a lightweight ready-mix for the skim and final coat, which is also what the manufacturers recommend.
Cinta y esquinero
El reveal y el L-bead son lo que hace posible un detalle sin moldura ni rodapié, y son lo menos indulgente del oficio: una línea perfectamente recta instalada de forma permanente contra tu trabajo.
All joints and all inside corners, with any compound.
Creased kraft paper with no adhesive — it is bedded in wet compound and the compound does the bonding. It has tensile strength along the joint and, more importantly, it resists compression, bending and shear, which is what an inside corner actually sees. The technique that matters: the bedding coat has to be wet and thin enough for the tape to sit into it. Overly dry material under the tape blisters.
Flat joints and patches, with setting-type compound only.
This is a rule, not a preference. The manufacturer literature is flat about it: if fiberglass tape is chosen, a setting-type compound must be used, and drying-type compounds are not recommended with it. The reason is mechanical — mesh does not bond to the board, so the compound has to be pushed through the mesh to grab the paper face on both sides. Wiping compound over the top of mesh conceals the joint and produces a significant increase in stress cracking, because the mesh ends up floating in a weak film with no shear strength. Mesh also does not belong in an inside corner, where it cannot form a crisp angle and where shear loads are highest. Paper tape there, every time. Manufacturers' instructions govern on their own products.
Outside corners in production work.
Fast, cheap, rigid, nailed or screwed on. It dents permanently — once a metal bead is dented the repair is replacement — and it can rust in a bathroom or in coastal air. Still the standard in a lot of tract work for good reason.
Bathrooms, coastal jobs, and any corner that takes traffic.
Rigid PVC, effectively immune to denting, will not rust, and it absorbs a little movement rather than telegraphing it. Stapled and set with adhesive. Our default within a couple of miles of the water.
Where the corner has to be dead straight and stay that way.
A thin metal core laminated to paper tape, bedded in compound and wiped down with a knife like a piece of tape. It gives the straightest corners available, and because nothing is fastened through it, it eliminates bead nail pops. It demands a full wet bed with no voids, though — installed dry or starved it can peel away from the wall later.
Spanish, Mediterranean and Santa Barbara style houses, which is a large share of the stock here.
A radiused outside corner instead of a sharp one. It changes the whole job, not just the corners: you need matching transition pieces at wall and ceiling intersections and at door returns, and splayed pieces at off-angle corners. Those get counted at takeoff, not discovered on hang day. Confirm the radius with the supplier before ordering so the transitions match.
Where drywall stops against another material and you want no trim at all.
Finishes an exposed drywall edge and the leg is coated with compound, so the board dies cleanly into stone, wood or a window return with nothing covering the joint. This is the trimless look, and it is a straightedge held against your work permanently.
A capped drywall edge where speed matters more than the detail.
Slips over the panel edge and caps it, leaving a small visible return. Faster than L-bead and honest about what it is — a utility detail rather than an architectural one.
A deliberate recessed line between planes. Also called a shadow bead.
A shadow reveal at the base instead of a baseboard, a reveal where drywall meets a slat wall, a reveal separating a dropped ceiling plane. This is the modern detail architects around here are drawing, and it is the least forgiving work in the trade: a reveal has to be laid out with the framer before anything is hung, because once it is in, every deviation in the wall reads against a perfectly straight line forever.
Long wall and ceiling runs, and wherever framing changes direction. Also called an expansion joint.
Not an option. GA-216 calls for control joints in walls in an uninterrupted straight plane exceeding thirty linear feet, in interior ceilings at fifty feet with perimeter relief and thirty feet without, in exterior ceilings and soffits at thirty feet, and wherever ceiling framing members change direction. Most long-run cracking traces back to a control joint that was never installed.
Papel en todas las esquinas interiores, siempre. Malla solo en planos, y solo con compuesto de fraguado. La malla no se adhiere al panel: el compuesto tiene que empujarse a través de la malla para agarrar la cara de papel de los dos lados. Pasada por encima con un compuesto blando listo para usar, la malla queda flotando en una película débil sin resistencia al corte, y se agrieta.
GA-216 las pide en paredes en un plano recto ininterrumpido de más de treinta pies lineales, en techos interiores a cincuenta pies con alivio perimetral y a treinta sin él, en techos exteriores y plafones a treinta pies, y dondequiera que los miembros del armazón del techo cambien de dirección. La mayoría de las grietas en tramos largos se remonta a una junta de control que nunca se instaló.
Los modos de falla, en detallePreguntas
No. Gypsum board has no fire-resistive rating in and of itself — that is AWCI's wording and it is the single most useful sentence on the subject. The rating belongs to the whole tested assembly: stud size and spacing, board type and thickness, orientation, fastener type, length and spacing, insulation, joint treatment. Substitute anything and you are outside the listing. Type X is what makes the assembly possible; it is not the rating, and no inspector treats it as one.
Type X has glass fiber in the core so it resists cracking as it calcines. Type C has more glass fiber plus vermiculite, which expands as the core is shrinking and roughly cancels it out, so the board stays dimensionally stable and does not pull away from the framing. All Type C is Type X; not all Type X meets the Type C requirements. Which means you can never send Type X where the plans call Type C — it can compromise the rating, and no argument about the board being thicker or better survives an inspection. It runs the other way fine.
It depends on the framing spacing and on whether the ceiling is getting texture. On 16 inch centers, 1/2 inch board applied perpendicular to the framing is fine. On 24 inch centers with a water-based texture coming, GA-216 requires either sag-resistant ceiling board or a step up to 5/8 inch — regular 1/2 inch is not compliant there, and that single rule explains nearly every wavy ceiling in a 1990s and 2000s tract house. Board always runs perpendicular to the framing on a ceiling.
No. Since the 2006 code cycle, tile backing in a tub or shower area has to be a cement backer unit, a fiber-cement backer, a glass-mat gypsum backer or a fiber-reinforced gypsum panel — not water-resistant gypsum. But do not over-correct either: green board is not banned from bathrooms. Painted bathroom walls and tiled walls outside the wet area can still use it, with the cut and exposed edges sealed per the manufacturer.
No, and this is the most expensive misunderstanding in bathroom construction. Cement board is water-durable — it will not rot or weaken when wet — but water passes through it. The waterproofing in a shower is a separate membrane, sheet or liquid-applied, either behind the board or on its face. Tile and grout are not waterproof either. A shower built on bare cement board with no membrane will fail behind the tile, and you will not know until it does.
No. It buys time. Mold-resistant board removes or treats the paper that mold feeds on, which matters in a humid bathroom, a laundry room or a coastal house. It does not make the wall waterproof and it does not fix a leak. If water is getting in, the board type is not the problem you have.
Paper for inside corners, always. Mesh only on flats, and only with setting-type compound — the manufacturer literature is flat about that, and the reason is mechanical. Mesh does not bond to the board; the compound has to be forced through the mesh to grab the paper face on both sides. Wiped over the top with a soft ready-mix, the mesh ends up floating in a weak film with no shear strength, and it cracks. Paper tape bedded properly is the strongest, most crack-resistant joint with any compound, which is why it is what we use on almost everything.
Setting-type compound. It hardens by chemical reaction rather than by drying, so it sets on a clock whether the room is cold, damp or airless, it shrinks very little, and it bonds harder. You cannot rework it once it goes. We reach for it on any heavy fill — a deep gap, a blown-out corner, a hole patch — because drying compound in a heavy fill shrinks, cracks and has to be refilled, sometimes twice. Also for same-day work, for bedding mesh, for laminating, for exterior soffits, and for first coats under a Level 5 or a dark paint, where less shrinkage means the joint is less likely to move after the paint is on.
Depends on the corner. Vinyl in bathrooms, in coastal air and anywhere the corner takes traffic, because metal dents permanently and a dented metal bead has to be replaced rather than repaired. Paper-faced metal where the corner has to be dead straight and where we want no fasteners in it. Galvanized metal in production work where it is fast and appropriate. Bullnose where the architecture asks for it, with the transitions counted at takeoff. If the drawings show reveals or L-bead, that conversation happens with the framer before anything is hung.
Yes, and the cost is mostly in layout and coordination rather than in the bead itself. A reveal is a perfectly straight line installed permanently against your work, so the framing behind it has to be right, the layout has to be set before hanging, and there is no fixing it afterward with compound. It is the best-looking detail in modern residential drywall and the least forgiving. We would rather walk it with the framer than repair it later.
Usually, yes. A constrained-layer damping panel puts a viscoelastic layer between gypsum layers and gets you into the useful range with one layer per side, which saves floor space, hanging labor and repeatability compared with two layers plus a damping compound. The other approach often performs comparably and can be cheaper in material. Neither one fixes a flanking path — back-to-back outlets, a duct that runs between the rooms, a continuous floor — and sealing the perimeter matters more than people expect. Tell us what you are trying to stop hearing and we will tell you which one is worth the money.
La calculadora cuenta paneles, compuesto, cinta, tornillos y esquinero, y muestra su aritmética. Para una lista real de compra sale de los planos — pero el orden de magnitud lo tienes en dos minutos.