Drywall is one of the most common interior wall and ceiling finishes used in construction today. But what exactly is behind those flat, painted panels? In this comprehensive guide, we’ll explore in detail what lies beneath drywall, including wall studs, framing, insulation, and more.
What is Drywall?
Drywall, also known as gypsum board or Sheetrock®, is made of a gypsum plaster core sandwiched between thick paper facings. Gypsum is a soft mineral that is mined and processed to create the drywall panels.
Drywall offers many benefits:
- It’s inexpensive and easy to install compared to other wall finishes like plaster.
- Drywall is fire resistant. The gypsum core contains crystalline moisture that releases when heated, delaying combustion.
- The seamless surface of drywall makes an ideal painting surface once properly finished.
- Drywall can be used to create curved or ornamental surfaces more easily than wood or plaster.
- Panels are available in various thicknesses from 1/4″ to 5/8″ to provide different levels of strength and sound insulation.
While incredibly versatile and popular, drywall alone lacks structural integrity and needs to be attached to wall framing or furring strips to create a solid interior wall or ceiling.
Wall Studs
Behind drywall are vertical wood or metal “wall studs” which make up the wall framing. Studs provide strength, rigidity, and a solid substrate to fasten the drywall panels.
Wood Studs
The most common type of stud used in modern construction is the wood stud. Wood studs consist of common dimensional lumber, usually 2×4 or 2×6 boards, spaced 16 inches on center. This means the studs are lined up vertically at intervals of 16 inches from the center of one stud to the center of the next.
Wood stud wall framing behind drywall, exposed
Wood provides good structural strength at a low cost. Softwoods like pine, fir, or spruce are common. The wood is kiln dried for stability.
2×4 and 2×6 refer to the dimensions of the lumber, which are not exact due to milling. Nominal sizes are:
- 2×4: 1.5″ x 3.5″
- 2×6: 1.5″ x 5.5″
Using these standardized sizes makes framing walls straightforward and modular with consistent spacing between studs.
Metal Studs
Another option is metal studs, which have become more common in commercial construction. Metal studs are thin galvanized steel or other alloys bent into a C-shape or into right angles resembling a “Z”.
Steel C-studs and Z-studs
Metal studs offer benefits like:
- High strength and fire resistance
- Dimensional stability unaffected by moisture
- Thinner profiles allowing more interior space
- Easy to cut and install
The downside is higher cost compared to wood. But for large commercial projects, the advantages of metal studs make them a popular choice. The thinner metal dimensions allow walls to have minimal thickness while maintaining strength.
Common metal stud sizes:
- 25 Gauge: 0.5″ thick x 1.5″, 2.5″, 3.5″, or 4″ wide
- 20 Gauge: 0.75″ thick x 1.5″, 2.5″, 3.5″ or 4″ wide
Spacing and Layout
Whether wood or metal, studs are positioned vertically and spaced every 16″ or 24″ on center. This regular spacing ensures the wall is strong and stable.
To lay out stud positions:
- Mark the floor and ceiling plates where studs will go, like at door openings or wall ends.
- Chalk a line across the bottom and top plates at 16″ or 24″ increments in between.
- Line up the studs at these marked intersections.
This creates a grid of studs at equal spacings across and vertically down the wall. Consistent, modular spacing allows for easy installation of drywall sheets later.
Typical layout for wood stud walls, spaced 16″ on center
Door or window openings require specialized framing and headers to maintain structural integrity. The framing and number of studs around these openings may vary from the typical spacing.
Overall, the consistent stud layout provides strength as well as reference points for locating studs once the drywall is installed.
Wall Plates
On each end of the wall studs sit a “top plate” and “bottom plate”. These boards sandwich the studs and tie the wall together.
Sole Plate
The sole plate, sill plate, or bottom plate is a board laid flat along the bottom of the stud layout. Typical plate material is:
- 2×4 or 2×6 lumber
- Oriented Strand Board (OSB)
- Plywood
The sole plate provides a solid anchoring point for the studs, preventing side-to-side movement. Ends of the plate rest on the subfloor. The bottom plate is usually anchored to the floor with nails or construction adhesive to stabilize the framed wall above.
Sole plate anchored to subfloor with adhesive and nails
With a sole plate secured to the floor, the vertical studs above are locked into position.
Top Plate
At the top of the wall, the “top plate” ties the studs together. Like the sole plate, top plates are commonly 2×4, 2×6, OSB, or plywood.
The top plate serves several purposes:
- Ties wall studs together side-to-side
- Provides attachment point for drywall above
- Stabilizes studs against bowing
- Forms connection point for walls or roof
For single-story walls, the top plate is often doubled with overlapping boards to form a stronger connection. For walls supporting roof loads or multiple floors, thicker double top plates may be used too.
Double top plate joins the studs and supports ceiling joists
Plates tie the wall stud framing together, ready for drywall installation.
Wall Heights and Ratios
Stud spacing and wall height are proportional to provide proper structural bracing. Typical wall heights with correlating stud spacing are:
- 8 foot walls – 16 inches on center
- 9 foot walls – 16 or 24 inches on center
- 10 foot walls – 24 inches on center
The shorter the wall, the closer the studs can be spaced when using full stud lengths. Taller walls need studs spaced further apart or require vertical splices to accommodate the height.
It’s important the framing is properly sized and reinforced to handle ceiling and roof loads above. Inspections ensure wall framing meets code requirements before drywall sheathing is applied.
Drywall Fastening
With the wall framing completed, drywall panels are fastened to the wood or metal studs and plates.
Screws are the main fastener used to attach drywall. Screws provide stronger holding power versus nails and minimize popping. Drywall screws have wide threads and a sharp point to bite into the stud face.
Drywall is commonly installed perpendicular to wood studs. A power drill/driver rapidly drives screws through the drywall into the framing behind. Screws are spaced every 12” along framing for maximum strength. The white drywall screws recess slightly below the paper surface.
For metal studs, self-tapping drywall screws are used. Screws are still spaced every 12” along metal studs and tracks. Screws joining drywall sheets together are staggered to prevent lumps. Proper drive depth seats screw heads just below the paper without tearing the facing.
Drywall screws spaced evenly across studs
Screws make an easy, strong drywall connection and allow for flexing movement in the wall. Nails are only used occasionally in drywall finishing for small patches or trim attachments.
Finding Studs Behind Drywall
Once drywall installation is complete, the wood or metal studs are hidden behind the smooth wall surface. However, locating them accurately is still important for attaching shelving, cabinets, or other wall mountings securely.
Here are some tips for locating studs:
- Use the standard 16” or 24” on-center spacing between studs. Measure over from a known stud to find others.
- Use a stud finder, which uses a magnet or electronic sensor to locate nails or screws in studs. Slowly scan the wall to pinpoint them.
- Look for drywall seams, which often align with studs, and measure over 16”/24”.
- Examine the wall surface for slightly raised screw/nail spots visible under lighting.
- Carefully probe the wall with a thin nail to feel for solid studs.
- Switch plates, outlets, or corner bead strips are often screwed into a stud, providing a reference point.
Finding and marking stud locations in advance makes hanging heavy items much easier and safer. Always confirm the stud center prior to drilling or inserting screws.
Fireblocking
For fire safety, building codes require structures to have fireblocking to slow the spread of flames through wall voids. Fireblocking consists of solid material inserted tightly in stud cavities to obstruct potential draft up or across.
Some common fireblocking materials:
- 2x lumber: Short 2×4 blocks nailed between studs.
- Fire-rated caulk: Beads of caulk installed in gaps at each stud bay.
- Rock wool insulation: High density mineral wool friction fits between studs.
- Drywall: Strips glued across bays.
- Fire-rated expanding foam: Applied in spaces.
Fireblocking lumber nailed at mid-height
Fireblocking divides up the stud cavities into smaller segments every 10 feet vertically, slowing any fire from spreading rapidly through the wall to the floor/ceiling space above.
Required fireblocking locations:
- Between floor levels including the attic
- At 10 foot intervals vertically
- Behind certain trim details
- At window/door openings
Consult local building codes to ensure proper fireblocking installation before enclosing walls. Homeowners undertaking renovations should also be aware of existing fireblocking when altering or removing walls.
Wall Insulation
Insulation is another important component behind drywall that increases energy efficiency and comfort. While not structural, insulation fills the voids between studs to resist thermal and sound transmission.
Common insulation types used in walls include:
- Fiberglass batts: Economical glass fiber insulation sold in rolls or batts sized to fit between wall studs. R-values from R-11 to R-15 in a 3.5” wall cavity.
- Mineral wool batts: Made of natural basalt or slag rock, with similar insulation performance as fiberglass.
- Cellulose: Shredded paper/cardboard treated with fire retardant fills wall cavities. R-13 to R-15 rating.
- Spray foam: Foam insulation sprayed directly into cavities expands and seals. Higher R value than batts. Costs more.
- Rigid foam boards: Polystyrene or polyisocyanurate cut to fit stud bays. R-values from R-4 to R-6.5 per inch.
Batts and cellulose are commonly used because they conform around pipes, wires, and obstructions in the cavity. Fiberglass and mineral wool resist heat flow, slowing temperature transfer.
Proper installation is important to achieve the full rated R-value. Insulation should fill the cavity without gaps, compression, or sagging.
Fiberglass insulation batts inserted into wall stud cavity
Insulation coupled with weather stripping reduces heating and cooling costs, keeps interiors more comfortable, and minimizes condensation within walls.
Moisture Barriers
Moisture infiltration into a wall can lead to mold, mildew, rotting studs, and sheathing damage. Rainwater seeping into wall cavities through the exterior siding can be a major issue.
On exterior walls, a moisture barrier is installed to protect wall framing by deflecting inbound liquid water and humidity.
Common types of moisture barriers for walls are:
- House wraps: Breathable membranes like Tyvek vapor-permeable air barriers allow water vapor diffusion while repelling bulk water. Wraps cover sheathing and lap over flashing.
- Plastic sheeting: Poly sheets like polyethylene vapor barriers stop moisture but don’t allow wall drying potential. Not breathable.
- Felt paper: Asphalt coated fiber sheets provide a water-resistive barrier. Traditional 15# or 30# felt paper is installed over sheathing.
- Insulated sheathing: Rigid foam panels add a water-resistive barrier to the wall plus extra insulation value.
Proper installation of siding, membranes, and flashing prevents leaks. Sealing penetrations like pipes and openings is also important to keep walls dry.
Applying house wrap over exterior wall sheathing
Water management and drainage planes in a wall assembly protect structural integrity.
Sound Insulation
For enhanced sound damping between rooms, specific construction techniques help reduce noise transmission through walls. Solutions include:
- Staggered studs: Separate rows of studs offset to eliminate direct sound transmission through framing.
- Double-layer drywall: Using two layers of drywall with offset seams and Green Glue adhesive/damping compound between absorbs more sound energy.
- Insulation: Cellulose, fiberglass, or rock wool batts muffler sound and dissipate vibrations.
- Resilient channels: These metal channels screw-attached horizontally over studs reduce sound transfer to drywall above.
- Drywall mass: Thicker quiet rock type drywall is heavier and improves acoustics.
A combination approach using staggered studs, multiple drywall layers, damping, and insulation provides optimal sound blocking for noise control. Proper perimeter sealing also minimizes flanking sound.
Double drywall layer with acoustic sealant and insulation absorbs sound
Attention to detailing at time of construction or during renovations can significantly improve wall sound reduction.
Electrical and Plumbing
Electrical wiring and plumbing pipework are often concealed inside wall cavities. Both should be correctly installed and marked for future access behind the drywall.
Electrical
Electrical wires routed through walls should run through bored holes in studs, protected by plastic grommets. Cables should not be pinched by insulation or stapled tightly. Leave slack for expansion.
Junction boxes are required for connections or transitions from solid to stranded wire. Outlet and switch boxes should anchor securely to studs. Use nail guards if necessary to avoid penetrating cables. Fireblocking must seal any gaps around wiring to stop fire spread.
Mark panel circuits at the breaker and label cables for easy identification. Keep wire runs as short and direct as possible.
Plumbing
Water supply lines and drains in walls should avoid joints which could leak. Use a single continuous length of pipe if possible. Where necessary, joints should be accessible or install inside boxes.
Avoid direct contact with insulation which may corrode or impair freeze resistance of pipes. Do not tightly compress insulation around pipes.
Label pipes and provide access panels for critical valves or drains. Install overflow pan liners under upstairs plumbing near ceilings.
Plan ahead for pipe routing and make sure electrical, insulation, and fireblocking will accommodate the plumbing layout.
Window and Door Openings
Windows and doors interrupt the standard stud spacing. These openings require specialized framing, headers, jack studs, and trimmers to maintain structural strength while removing stud sections.
Headers
The header is the horizontal support beam across the top of the window or door opening. This bears the weight of wall structure above. Headers are typically double 2x lumber or engineered I-joists sized to span the opening.
For large openings, a built-up header may be required using multiple layers of lumber or plywood. Metal headers are also an option.
Pre-assembled window header unit will be lifted into place
The header transfers loads from above down to the jack studs and king studs at the sides of the openings.
Jack and King Studs
Next to the opening, jack studs run from the bottom plate up to support the header. Short studs called cripples help tie the whole unit together.
The king studs run full height from bottom plate to top plate and provide lateral stability as well as attachment for window or door jambs.
Blocking reinforces between the jack and king studs. The number of jack studs varies based on opening size and load requirements. Framing anchors also connect the components.
This framing method allows large spans to be safely opened up in walls while redirecting structural forces around the perimeter.
Specialized framing supports header over opening
Careful layout and assembly ensures the wall is reinforced despite having openings.
Advanced Framing Techniques
Many new construction