Studs, Insulation, Wiring, Plumbing, Air Ducts, and Everything Behind the Drywall.
Most homeowners spend years looking at their walls without knowing what's behind them.
A typical wall may contain wood framing, electrical wiring, plumbing, insulation, heating and cooling ducts, and other components. Some walls also help support the weight of the house.
How Is a Typical Wall Built?
Most Michigan houses use wood-frame construction.
A typical framed wall includes:
Studs: Vertical pieces of lumber that form the wall's framework.
Top plate: Horizontal framing along the top of the studs.
Bottom plate: Horizontal framing along the bottom.
Drywall: Panels attached to the framing to create finished interior surfaces.
Insulation: Material installed where thermal or sound control is needed.
Wiring: Electrical cables routed through framing cavities.
Plumbing: Water supply, drain, and vent pipes where needed.
Ductwork: Heating and cooling air passages found in certain walls.
Studs are commonly spaced 16 inches on center, although 24-inch spacing and other arrangements are also used.
Older homes may have plaster over wood lath instead of drywall.
What's the Difference Between Interior and Exterior Walls?
Interior walls divide rooms, provide privacy, and sometimes support the structure above them. They may contain wiring, plumbing, ductwork, and sound insulation.
Exterior walls separate the conditioned living space from the outdoors. They usually include additional materials for weather protection and energy efficiency.
A common modern exterior wall assembly, working from inside to outside, includes:
Interior drywall.
Wood studs and cavity insulation.
Structural sheathing, often OSB or plywood.
A water-resistive barrier.
Exterior siding or another cladding material.
Some assemblies also use continuous exterior insulation, an interior vapor retarder, or specialized air-sealing materials.
The exact layers depend on the home's age, construction method, and applicable building code.
What Are Wall Studs?
Studs are the vertical framing members behind most finished walls.
Common wood stud sizes include:
2×4 lumber: Actual dimensions approximately 1½ × 3½ inches.
2×6 lumber: Actual dimensions approximately 1½ × 5½ inches.
Exterior walls often use 2×6 framing to provide additional insulation space, although 2×4 exterior walls remain common.
Studs also provide fastening points for cabinets, shelving, televisions, and other wall-mounted items.
A stud finder can help locate them, but plumbing, electrical wiring, and other systems may also be present within the wall.
What's Around Windows and Doors?
Openings interrupt the normal pattern of studs, so additional framing is used.
Common components include:
Header: A horizontal member above an opening that transfers loads when structural support is required.
King studs: Full-height studs beside an opening.
Jack studs: Shorter studs that support a header.
Cripple studs: Short studs above or below certain openings.
Rough sill: Framing beneath a window opening.
Header sizes and framing arrangements vary depending on the loads and the wall's structural purpose.
Windows also require proper installation, flashing, and insulation around the opening. For more on window construction and performance, read Home Window Basics: Types, Materials, Efficiency, and Replacement.
What's Inside an Exterior Wall?
Insulation helps slow heat transfer between the home and the outdoors.
Common insulation materials include:
Fiberglass batts.
Mineral wool.
Blown-in cellulose.
Spray foam.
Rigid foam insulation.
Insulation performance is commonly expressed as an R-value. Higher R-values indicate greater resistance to heat flow.
Air sealing is another important part of wall performance. Gaps around framing, electrical boxes, and penetrations can allow air movement that reduces comfort and energy efficiency.
Where Does Electrical Wiring Run?
Electrical cables commonly travel vertically or horizontally through wall cavities.
Wiring may pass through holes drilled in studs or run alongside framing members.
Inside walls, you may find:
Electrical cables.
Outlet and switch boxes.
Wiring for lighting fixtures.
Low-voltage communication cables.
Wiring for thermostats and security systems.
Modern framing practices use protective steel plates where wiring or piping is close enough to the stud surface to be vulnerable to nails or screws.
Electrical wiring is one reason to investigate before drilling deeply into a wall.
To learn more about outlets, circuit breakers, electrical panels, and older wiring, read Home Electrical Basics.
What About Plumbing?
Walls near kitchens, bathrooms, and laundry rooms often contain plumbing.
Common components include:
Hot and cold water supply pipes.
Drainpipes.
Plumbing vent pipes.
Shower valve assemblies.
Connections serving sinks, toilets, and other fixtures.
Supply piping may be copper, PEX, CPVC, or another approved material.
Older Michigan homes may contain galvanized steel supply pipes or cast-iron drainpipes.
Drain and vent pipes often require larger wall cavities or specially planned framing.
For a closer look at pipe materials, water supply, drains, and plumbing systems, read Home Plumbing Basics: What Buyers and Homeowners Should Know.
What About Heating and Cooling Ducts?
Some interior walls contain ductwork that distributes heated or cooled air throughout the house.
Common components include:
Supply ducts: Carry heated or cooled air from the furnace or air handler to rooms.
Return air pathways: Allow air to travel back to the heating and cooling system.
Wall registers: Openings where air enters or leaves a room.
Vertical duct runs: Carry air between floors.
Ductwork is commonly made from galvanized sheet metal, although other approved materials are also used.
In many Michigan homes, larger ducts run through basements, crawlspaces, or attics, with smaller branches extending into walls and floors.
Not every wall contains ductwork. Some homes use floor or ceiling registers, and others have heating systems that don't require air ducts.
For more information about furnaces, air conditioners, heat pumps, and ductwork, see Home Heating and Cooling Basics.
What's Inside a Load-Bearing Wall?
Some walls carry structural loads from the roof, upper floors, or other parts of the house.
These are called load-bearing walls.
Their framing transfers weight through studs, headers, beams, and other structural members toward the foundation.
Other interior walls primarily divide spaces and are called non-load-bearing partitions.
Wall location, joist direction, framing plans, and the support system below can help identify a load-bearing wall. Structural evaluation establishes how the wall functions before it is altered.
What's Different About Walls in Older Michigan Homes?
Wall construction has changed considerably over the decades.
Early 1900s homes: May have plaster and wood lath, balloon framing, masonry walls, or other older construction methods.
1940s–1960s homes: Often feature conventional wood framing, plaster or drywall finishes, and insulation levels that differ from modern expectations.
1970s–1990s homes: Commonly use drywall, fiberglass insulation, plywood or OSB sheathing, and evolving air- and moisture-control practices.
Newer homes: Frequently incorporate improved air sealing, insulation systems, engineered framing products, and modern weather barriers.
If you're purchasing an existing house, Home Inspection Basics explains what a general inspection covers and why concealed wall components are not always accessible.
Understanding Your Home Starts Behind the Drywall
Walls do much more than separate rooms.
They support structural loads, carry utilities, manage temperature and moisture, and provide surfaces for everyday living.
Knowing what's inside them helps homeowners maintain their property and gives buyers a better understanding of how a house is constructed.
Explore more topics in the SoldByCaleb Real Estate Guides.