Quick answer
Drywall is a building panel made of a noncombustible gypsum core with paper bonded to both faces, fastened to studs or joists to form the interior surface of walls and ceilings, then taped, coated with joint compound and painted.
Its formal name is gypsum board, defined in ASTM C1396. “Sheetrock” is one maker’s brand name. Versions exist for fire separation, damp rooms and tile backing.
Quick facts
The key facts about Drywall, with sources:
- Formal name
- Gypsum board (gypsum wallboard) 1
- Core
- Noncombustible, essentially gypsum, with paper bonded to it 1
- Product standard
- ASTM C1396 covers wallboard, ceiling board, water-resistant backing board and Type X 1
- Finish scale
- Levels 0 to 5 in Gypsum Association GA-214 2
- Garage-to-house wall (model code)
- At least 1/2 in gypsum board on the garage side 3
- Living space over a garage
- At least 5/8 in Type X gypsum board 3
Key takeaways
- Drywall, gypsum board and Sheetrock all name the same kind of panel: a gypsum core with paper faces.
- The type matters more than the brand: regular, Type X for fire separation, moisture-resistant and glass-mat boards each have a job.
- Codes set where some boards are required, such as the wall and ceiling between an attached garage and the house.
- How smooth the wall looks depends on the finish level, 0 to 5, which your quote should name.
- Wet drywall that stays wet for more than a day or two can grow mold; fix the leak and dry it fast.
What drywall is made of
A sheet of drywall is a sandwich. The middle is a core of gypsum, a soft mineral that holds chemically bound water. Paper is bonded to the front and back. ASTM C1396, the U.S. product standard for gypsum board, says the core is noncombustible and “essentially gypsum,” with paper bonded to it 1.
The name “drywall” comes from how it is installed. Older walls were plaster, troweled on wet over wood or metal lath and left to cure.
Drywall arrives as finished sheets, so the only wet work is the joint compound at the seams and screw heads. That is the main reason it replaced plaster in most American homes.
ASTM C1396 groups several products under one standard: gypsum wallboard for decorated walls and ceilings, predecorated board, backing board and coreboard for layered systems, water-resistant gypsum backing board, and gypsum ceiling board 1. The test list behind those names includes nail pull resistance, flexural strength, humidified deflection (sag) and water resistance 1.
How a drywall wall comes together
Every drywall surface is built in the same order. The finish crew’s work is only as good as the hanging underneath it.
- Framing is checked. Studs or joists must be straight and on layout. A bowed stud shows through the finished wall.
- Boards are hung. Sheets are screwed or nailed to the framing, ceilings first, then walls. The fastener spacing comes from the building code table for gypsum board attachment and the maker’s guide 3.
- Corners get bead. Metal, vinyl or paper-faced corner bead protects outside corners.
- Joints are taped. Paper or mesh tape is bedded in joint compound over every seam 4.
- Coats are added. More coats of compound are spread wider and feathered thin, with drying time between each 4.
- Surface is sanded and primed. The finish level sets how many coats and whether a skim coat covers the whole wall 2.
- Check framingStraight, on layout
- Hang boardCeilings first
- Bead corners
- Tape jointsTape in compound
- Add coatsDry between each
- Sand and primeTo the specified level
The number of coats in the last steps depends on the GA-214 finish level written into the job. Source: [2] [4]
Types of drywall and where each belongs
| Board type | What it is for | Typical place in a home |
|---|---|---|
| Regular gypsum wallboard | Walls and ceilings that will be decorated 1 | Bedrooms, living areas, hallways |
| Type X (fire-rated) | Enhanced fire resistance where a code calls for it 3 | Ceiling under living space above a garage |
| Gypsum ceiling board | Ceilings, with more resistance to sag 1 | Ceilings with wider joist spacing or heavy textures |
| Water-resistant gypsum backing board | A base for tile in some locations 1 | Older practice behind tile; limited in wet showers |
| Glass-mat or fiber-reinforced panels | Faces without paper; covered by GA-214 finish levels 2 | Basements, damp rooms, some tile backers |
| Cement board (not drywall) | Portland-cement panel for tile in wet areas 5 | Shower and tub walls |
Example: reading the drywall lines on a garage-conversion quote
A homeowner adds a bedroom above an attached garage. Here is how the drywall lines on the plan line up with the model code table as reproduced in the City of Boise’s 2022 handout 3. Your jurisdiction may amend these rules.
| Surface | What the model code table asks for | What to look for on the quote |
|---|---|---|
| Garage ceiling under the new bedroom | At least 5/8 in Type X gypsum board 3 | “5/8 Type X” named, not just “5/8 drywall” |
| Wall between garage and house | At least 1/2 in gypsum board on the garage side 3 | Garage-side board included, not left bare |
| Structure supporting that floor | At least 1/2 in gypsum board 3 | Beams or posts in the garage covered |
| Fastening | Attachment per the code’s gypsum board table 3 | Screw spacing checked at inspection |
| Door from garage to house | Solid wood or steel at least 1 3/8 in thick, or 20-minute rated, self-closing 3 | Door spec listed with the drywall scope |
The detail that trips up remodels is the ceiling: a plain 5/8 in board is not the same as 5/8 in Type X. Ask the contractor to name it, and keep the label photos for the inspector. The permits and approvals guide explains when this kind of work needs a permit.
Where drywall shows up in a remodeling project
In the scope of work. Expect separate lines for hanging, taping and finishing, with board thickness, board type and finish level. A clear scope of work spells these out instead of saying “drywall as needed.”
On the plans. Fire-separation walls and ceilings are often marked with a board type, such as “5/8 Type X.” Wet-area walls may call for a different backer than drywall entirely.
At inspection. Many jurisdictions inspect fire-separation board before tape goes on, because the fastener pattern disappears under compound. This happens after the rough-in inspection of framing, plumbing and wiring.
On the board itself. The printed edge or back of each sheet usually names the product, thickness and type. Photos of those labels are the easiest proof that the right board went up.
Name the finish level in the contract
Two crews can both “finish drywall” and deliver very different walls. Writing the GA-214 level (for example, Level 4 for flat paint or Level 5 under glossy paint and raking light) gives you a shared standard to check against 2.
Why drywall is the default wall finish, and its weak spots
Strengths
- Noncombustible gypsum core 1; Type X versions are used in code-required fire separations 3.
- Fast to install compared with wet plaster, because the panels arrive finished.
- Easy to patch: a damaged area can be cut out and replaced with a new piece and compound.
- Takes many finishes, from heavy texture to the smooth Level 5 surface 2.
Limits: water, impact and perfect flatness
Water is the main limit. EPA advises drying water-damaged areas within 24 to 48 hours to prevent mold and notes that mold can hide on the back side of drywall 6. Board that has stayed wet is usually cut out and replaced, not dried in place.
Flatness is the second. The Gypsum Association’s finish guidance accepts that a perfectly flat gypsum surface is not achievable, which is why it pairs finish levels with lighting and paint sheen 2. A long hallway lit by a window at the end will show more than a textured bedroom wall.
Impact is the third. Garages, mudrooms and stair walls take knocks. Thicker board, abuse-resistant products or wainscot help, but no gypsum board is as hard as plaster or tile.
What drives drywall cost, and how long it lasts
We do not publish drywall prices. What moves the cost is labor more than board: the number of sheets, ceiling height, how many corners and openings there are, whether the board is Type X or moisture-resistant, and above all the finish level.
Each step up in GA-214 adds coats and sanding time, and Level 5 adds a skim over the whole surface 2. Repair work costs more per square foot than new walls because of setup, matching texture and dust control.
Installed and kept dry, gypsum board lasts as long as the house. What ends its life is water, impact or a remodel that opens the wall. For a whole-project number, our whole-home budget tool and the remodeling cost guide show where interior finishes sit in the total.
Who installs it and in what order
Drywall is usually hung by one crew and finished by another, often called tapers or finishers. On permitted work, the inspector’s visits shape the schedule.
- Framing, plumbing, wiring and ductwork are finished and pass their rough inspections.
- Insulation goes in and, where required, is inspected.
- Board is delivered and kept dry and flat until it is hung.
- Ceilings are hung first, then walls, with joints staggered and fasteners per the code table 3.
- Fire-separation board is inspected before taping where your jurisdiction requires it.
- Taping and finishing coats are applied with drying time between each; USG asks for at least 55°F in the building during finishing 4.
- The surface is sanded, primed and painted, then reviewed under the room’s real lighting.
Keeping drywall in good shape
- Keep indoor humidity in range. EPA suggests below 60%, ideally 30% to 50% 6.
- Run the bath fan when showering. Steam is the main source of moisture on bathroom walls 6.
- Fix small cracks at seams early. Recurring cracks at the same joint can point to framing movement.
- Use wall anchors rated for the load. Hollow drywall alone does not hold heavy shelves or TVs.
- Keep spare board and touch-up paint from the job for patches that match.
Warning signs and when to call a pro
- Brown stains or soft, bulging spots: a leak behind or above the board.
- Musty smell or dark spotting: possible mold; EPA advises professional help above about 10 sq ft 6.
- Popped screw or nail heads in rows: framing movement or wrong fastening.
- Diagonal cracks from door and window corners: may reflect settling; a structural question, not a patch job.
- Sagging ceiling board: wet board, wide joist spacing or a heavy texture on thin board.
Dust from old walls can carry lead or asbestos
In homes built before 1978, cutting or sanding painted drywall can release lead dust, and EPA’s RRP rule requires certified firms for paid work that disturbs those surfaces 7.
Older wall and ceiling materials can also contain asbestos; EPA advises sampling by an accredited professional before a remodel disturbs them 9. Joint compounds containing respirable asbestos were banned for consumer sale under 16 CFR Part 1304 8.
Codes and standards that govern drywall
Product standard. ASTM C1396 is the U.S. standard specification for gypsum board. It lists the board types and the physical tests they must pass, and it points to ASTM C840 for application 1.
Model building code. The International Residential Code (IRC), as adopted by states and cities, uses gypsum board in fire-separation rules.
In the IRC table reproduced by the City of Boise in 2022, the wall between an attached garage and the house needs at least 1/2 in gypsum board on the garage side, and habitable rooms above a garage need at least 5/8 in Type X; attachment follows the code’s gypsum board fastening table 3.
Local adoption and amendments vary, so ask your building department which edition applies.
Finish standard. Gypsum Association GA-214 sets the Level 0 to 5 finish scale, issued with other trade groups and updated in a 2022 quick reference guide 2.
Health rules. EPA’s RRP rule covers paid work that disturbs paint in pre-1978 homes 7; asbestos rules apply when old materials test positive 9.
Drywall vs plaster vs cement board
| Material | How it goes up | Water tolerance | Best use |
|---|---|---|---|
| Drywall (gypsum board) | Sheets fastened, then taped and coated 4 | Poor if left wet 6 | Most interior walls and ceilings |
| Traditional plaster | Wet coats over lath | Better than paper-faced board, still damaged by leaks | Restoration of older homes |
| Cement backer board | Sheets fastened, joints taped with alkali-resistant mesh 5 | Does not soften or rot when wet 5 | Behind tile in showers and tub surrounds |
| Glass-mat gypsum panel | Hung like drywall; finished to GA-214 levels 2 | Better mold and moisture resistance than paper faces | Basements and damp rooms |
Drywall myths
- Myth Sheetrock is a different material from drywall.
- Reality Sheetrock is a USG brand name for gypsum board 41.
- Myth Green board is fine inside a shower.
- Reality Water-resistant gypsum backing board is a different product from cement board; showers usually call for a cement or other wet-area backer plus waterproofing 5.
- Myth Any 5/8 in board is fire-rated.
- Reality Fire separations call for Type X specifically, not just thickness 3.
- Myth Wet drywall will be fine once it dries.
- Reality EPA warns mold can grow if materials are not dried within 24 to 48 hours, sometimes out of sight on the back face 6.
- Myth “Smooth finish” means the same thing to every crew.
- Reality GA-214 defines six distinct levels; name the one you want 2.
Local variables: code adoption and humidity
Drywall is sold the same way nationwide, but two things change by place.
First, code adoption: states and cities adopt different IRC editions and amend the garage-separation and fastening tables, so the board your inspector wants can differ from a neighboring town 3.
Second, climate: homes in humid regions, or basements anywhere, push drywall toward moisture-resistant or glass-mat panels and make humidity control more important 6.
Choosing the right board for each room
Start with the room’s job. Living spaces take regular board finished to Level 4 under flat paint. Fire separations take Type X where the code says so. Damp rooms and basements lean to moisture-resistant or glass-mat panels. Inside showers, use a cement or wet-area backer with a waterproofing layer, not paper-faced drywall.
Then match the finish to the light and paint. If you plan glossy paint or a wall lit from the side, budget for Level 5. For help comparing bids that list these items differently, use the quote comparison tool.
- If Habitable room above an attached garage
- Then 5/8 in Type X on the garage ceiling, per the adopted code 3
- If Wall shared with an attached garage
- Then At least 1/2 in gypsum board on the garage side 3
- If Shower or tub wall that gets tile
- Then Cement backer board plus waterproofing, not standard drywall 5
- If Basement or damp room
- Then Moisture-resistant or glass-mat panels; control humidity 6
- If Glossy paint or strong side light
- Then Specify a Level 5 finish 2
Questions about Drywall
Is drywall the same as Sheetrock?
Yes, in practice. Drywall is the common name for gypsum board, the panel defined by ASTM C1396. Sheetrock is a brand name made by USG. Other makers sell the same kind of panel under their own names. When you compare quotes, look at the board type and thickness rather than the brand.
What is drywall made of?
Drywall is a core of gypsum with paper bonded to the front and back. ASTM C1396 describes the core as noncombustible and essentially gypsum. Some panels replace the paper with glass mat, and Type X boards add ingredients that improve fire resistance. The core is why drywall slows fire but is damaged by water.
What thickness of drywall is used for walls and ceilings?
Half-inch board is common for walls, and 5/8 inch is common for ceilings and fire separations. Codes set specific minimums in some places: the IRC table reproduced by Boise in 2022 requires 5/8 inch Type X under living space above a garage. Check your local code and the plans for the exact thickness.
What is Type X drywall?
Type X is gypsum board made for better fire resistance than regular board.
Codes call for it in specific places, such as the ceiling of an attached garage with a bedroom or other living space above it.
A plain board of the same thickness does not count, so ask the contractor to name Type X on the quote.
Can drywall be used in a bathroom?
Yes, outside the shower and tub area, as long as the room has an exhaust fan and moisture is controlled. EPA recommends running the bathroom fan when showering to keep moisture down. Inside a tiled shower, installers use cement board or another wet-area backer with a waterproofing layer instead of paper-faced drywall.
What are drywall finish levels?
They are a six-step scale, Level 0 to Level 5, set out in Gypsum Association GA-214. Level 0 has no taping at all.
Level 4 is the usual finish for flat paint in homes. Level 5 adds a thin skim coat over the whole surface for glossy paint or strong side lighting. Naming a level avoids arguments later.
Does wet drywall need to be replaced?
Often, yes. EPA says wet materials should be dried within 24 to 48 hours to prevent mold, and that mold can hide on the back of drywall.
Board that has sagged, softened or stayed wet longer is usually cut out and replaced after the leak is fixed. Small, quickly dried spots may only need a stain-blocking primer.
Do you need a permit to replace drywall?
It depends on your city and the scope. Patching or replacing a small area is often exempt, while larger jobs, fire-separation walls and work that opens framing, wiring or plumbing usually need a permit and inspection. Check with your building department or use a permit lookup before work starts.
Can old drywall contain asbestos?
Older wall systems may. The concern is mostly the joint and patching compounds, which the Consumer Product Safety Commission banned from containing respirable asbestos in 1978, and some older textures. EPA advises having suspect materials sampled by an accredited professional before a remodel disturbs them. Do not sand old walls until you know.
Sources
- ASTM International, C1396/C1396M Standard Specification for Gypsum Board (summary page), retrieved .
- Gypsum Association, GA-214-2022 Recommended Levels of Finish for Gypsum Panel Products, Quick Reference Guide (hosted by CISCA), retrieved .
- City of Boise, IRC Code Handout #435: Dwelling/Garage Separation (Feb 2022), retrieved .
- USG, Sheetrock Brand All Purpose Drying-Type Powder Joint Compound submittal sheet, retrieved .
- USG, Durock Brand Cement Board with EdgeGuard Installation Guide, retrieved .
- U.S. EPA, A Brief Guide to Mold, Moisture and Your Home, retrieved .
- U.S. EPA, Lead Renovation, Repair and Painting Program, retrieved .
- Code of Federal Regulations, 16 CFR Part 1304, Ban of Consumer Patching Compounds Containing Respirable Free-Form Asbestos (via Cornell LII), retrieved .
- U.S. EPA, Protect Your Family from Exposures to Asbestos, retrieved .
Expert review
Written by the HyreRemodel Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Board definitions and types come from the ASTM C1396 summary page; finish levels from the Gypsum Association GA-214-2022 quick reference guide.
Garage-separation requirements are quoted from a 2022 City of Boise handout that reproduces IRC Table R302.6, because the ICC code viewer blocked automated access on the retrieval date; local amendments vary. Moisture, lead and asbestos guidance is from EPA. No prices are given.
Suggest a correction. We fix errors and say what changed.