The board on the takeoff is not “drywall.” It is a thickness, a core, a facer, and — on anything rated — a named product in a tested design. Substituting leftover 1/2-inch regular for 5/8 Type X is how a drywall sub inherits a failed inspection.
This guide is for estimators and PMs who have to pick a SKU that the hanger can get this week and that still matches the spec. Brand examples point at manufacturer listings. Current fire designs live in UL Product iQ and in each manufacturer’s assembly library — USG, Georgia-Pacific, American Gypsum, PABCO, National Gypsum, CertainTeed.
Paper-faced interiors are generally ASTM C1396. Glass-mat panels have their own standards. Abuse/impact classification is ASTM C1629. None of those replace a UL design number.
Regular (standard) interior board
Paper face, gypsum core, tapered edge. Common thickness 1/2 inch on residential walls with studs at 16 inches. 5/8 inch regular (non-Type X) exists but is not a fire-rated core.
Use: interior partitions and ceilings that are not rated and not wet, where span and sag limits are satisfied.
Do not use: a fire-rated design that calls for Type X or Type C; a wet tub/shower wall that wants tile backer; a 24-inch o.c. ceiling that wants sag-resistant ceiling board.
Residential production lives on 1/2-inch regular and 1/2-inch ceiling board. Commercial interiors live on 5/8 Type X even when the wall is not rated, because one stocked thickness simplifies the truck.
Ceiling / sag-resistant board
Formulated so 1/2-inch panels can run on 24-inch ceiling framing without the sag you get from regular 1/2-inch in humid conditions. Manufacturers label these as interior ceiling board or sag-resistant.
Use: residential and light commercial ceilings at 24 inches o.c. when the spec allows 1/2-inch.
Do not assume regular 1/2-inch wallboard is the same SKU. If the job is 16-inch joists and a texture ceiling, confirm before you over-specify.
Type X
ASTM C1396 Type X — glass fiber in the core, usually 5/8 inch for a 1-hour claim in listed single-layer designs, with 1/2-inch Type X appearing in some 45-minute / specific assemblies. Type X is the default “fire-rated drywall” on residential garage separations, multi-family demising, and commercial partitions.
Use: wherever the design or the code calls for Type X by name.
Not automatic: “5/8-inch” is not Type X unless the core is Type X. “Type X” is not a license to ignore the rest of the UL design (layers, orientation, fasteners, insulation, joints).
Type C
Type C is an industry designation, not a separate ASTM type with its own letter in C1396. It is an enhanced Type X-style core — more fiber and typically a shrinkage-compensating additive (often vermiculite) that expands as gypsum calcines. It is used where the tested design calls for Type C (some 2-hour single-layer walls, some floor-ceilings, some shaft and column designs).
Bid rule: if the UL design says Type C, you hang Type C. Type X is not a silent substitute. If the design says Type X, Type C often may be used as an upgrade when the manufacturer lists it — confirm, do not assume.
Georgia-Pacific and others have public explainers on this exact mix-up. The design number wins.
Moisture- and mold-resistant (MR) paper-faced
Treated face paper and an improved core. Still paper-faced gypsum, still ASTM C1396. Common in 1/2-inch and 5/8 Type X. Green or purple face paper is a brand cue, not a performance spec — read the product data.
Use: interiors with higher humidity that are not a tile-in-shower substrate: bathrooms (walls that get paint, not thinset), laundry, some basements, behind vapor-closed finishes the spec allows.
Do not use as the tile backer in a wet shower. Paper-faced MR is the wrong product there. Use cement board or a glass-mat tile backer the tile manufacturer accepts. This is one of the most expensive “we always use green board” habits in residential work.
MR Type X exists for rated walls in humid spaces. The rating still comes from the design, not the color of the paper.
Glass-mat interiors and sheathing
Fiberglass mat instead of paper. Better mold resistance and, on exterior products, a prerock / weather window the paper interiors do not have. Interior glass-mat (DensArmor-type, GlasRoc interiors, and peers) can be specified for healthcare, prerock, and abuse. Exterior glass-mat sheathing (DensGlass and peers) is a sheathing product — different ASTM, different fasteners, different finish (it is not a Level 4 paper wall).
Finishing glass-mat to a smooth paint level is slower. Budget Level 5 or the manufacturer’s primer-surfacer system.
Shaftliner
Typically 1-inch, 24-inch-wide, Type X (paper or glass-mat) liner panels for cavity shaftwall and area-separation walls. Double-beveled edges drop into J-runners and shaft studs. See steel stud framing basics.
Use: elevator and stair shafts, mechanical shafts, multi-family area separation — the systems in the manufacturer’s shaftwall catalog.
Do not rip 5/8 Type X into 24-inch strips and call it liner. Wrong thickness, wrong edge, wrong listing.
Glass-mat liners (PABCO GLASS shaftliner and peers) are sold for longer weather exposure on open shafts. Paper liner is not a rainscreen.
Abuse-resistant and impact-resistant
ASTM C1629 classifies surface abrasion, indentation, soft-body and hard-body impact. Abuse-resistant is the corridor / backpack product. Impact-resistant adds a mesh or dense core for carts, gurneys, and gym walls.
Usually 5/8 Type X, often mold-resistant. Hang like standard board; finishing a glass-mat abuse face may need extra skim.
Use: schools, hospitals, stairwells, loading, rec rooms. Price the board and the extra knife time. A Level 4 spec on impact board in critical light is still Level 4 on a harder panel — it will not hide a bad hang.
Sound panels
Constrained-layer / viscoelastic panels (QuietRock and CertainTeed SilentFX-type products) are a different SKU and a different cut. They can replace multiple layers in some acoustic designs. They do not replace a Type X layer unless the acoustic and fire documents say so.
Price blades, weight, and the manufacturer’s joint details. Do not assume a production taper’s Level 4 rate.
Thickness, width, and the truck
| Thickness | Typical role |
|---|---|
| 1/4 in. | Curves, laminate overlay |
| 3/8 in. | Remodel overlay, some manufactured housing |
| 1/2 in. | Residential walls; sag-resistant ceilings |
| 5/8 in. Type X | Commercial default; rated walls and ceilings |
| 1 in. | Shaftliner / coreboard |
48-inch vs 54-inch width is a joint-count and hang-pattern decision on 9-foot residential walls (horizontal 54 covers 9 feet with one sheet). 8- to 16-foot lengths: longer board cuts butts, needs lifts, and does not fit every stair. Commercial metal stud at 10-foot walls wants 10-foot vertical stock if the fire design allows vertical.
Takeoff habits that keep inspections
- Read the UL / GA-600 design product name, not just “5/8 firecode.”
- Separate liner, Type C, glass-mat, and abuse onto their own lines.
- Wet areas: tile backer ≠ MR paper.
- Ceilings at 24 inches o.c.: ceiling board or 5/8, not leftover wall 1/2.
- Control joints and finish level do not change because the core changed, except that glass-mat may need more skim.
- Substitutions go through the design professional and the AHJ, not through the lumber counter.
Related directory
Manufacturers — USG, CertainTeed, National Gypsum, Georgia-Pacific, American Gypsum, PABCO. Steel that holds the liner: Steel stud / framing.
FAQ
Can I swap Type X for Type C to save a layer?
Only if a listed design says that Type C product, that thickness, that layer count. You cannot invent a 2-hour wall by upgrading the core on a 1-hour Type X design.
Is purple or green board waterproof?
No. It is moisture- and mold-resistant paper-faced gypsum. It is not a shower pan.
Why is the commercial job all 5/8 Type X if some walls are not rated?
One thickness, one fastener length, one rated stock on the floor. That is a production choice. It is still Type X, not regular 5/8.
Does shaftliner need finishing?
The liner face inside the shaft is usually not a paint-grade Level 4. The occupant-side face layers are finished to the schedule.
Can glass-mat sheathing be the interior finish?
Not as a paper-face Level 4 wall. Interior glass-mat products are finished to their own system. Exterior sheathing is a substrate for cladding.