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Drywall walls iStock

We don’t often think about walls except as a place to hang pictures, or maybe as something that prevents the downstairs of your house from having an open floor plan with long interior views.

Without walls though, your house won’t stand up. Obviously, outside walls keep out the weather and support the roof and floors. But interior walls serve many purposes as well, including supporting floor and ceiling loads, providing chases for running pipes, wires, and ducts, as well as making baths and bedrooms private places.

Wall Structure

Interior or exterior, most walls are built in a similar way from 2x4s or 2x6s (used in exterior walls to allow for more insulation). Long pieces of lumber called plates run along the top and bottom of the wall. Vertical members called studs are placed every 16 inches or 24 inches so that the ends of standard 4x8 plywood or OSB sheathing panels, as well as drywall panels, always land in the middle of a stud and can be fastened. (In houses built before standardized panels, stud spacing was actually often random.)

Studs carry the weight of the floor or roof above down toward the foundation. Where you can’t have studs, such as at doors and windows, horizontal beams called headers span the opening. Jack studs cut to fit beneath the header ends carry its load downward. King studs are full size studs nailed to the sides of jack studs and the ends of the header to stabilize the assembly. A rough sill forms the bottom of a window opening, and short studs called cripples fill in below it. Cripples are also used to fill in between the header and the top plate in cases when the header doesn’t completely fill that space.

Exterior walls are covered with sheathing, usually plywood or oriented strand board (OSB). Sheathing gives stud walls rigidity—without it, walls could collapse along their length. Older houses might have sheathing made of boards, often run at an angle to create rigidity through triangular bracing. Some new homes are sheathed with rigid foam and braced with steel straps that run diagonally. The bracing on old timber framed houses was integral to the wall structure, so these often have no sheathing, with the siding applied directly to the studs.

Get Curb Appeal with New Siding

Siding is the exterior cladding of a wall. It can be wood clapboards or shingles, or newer materials such as fiber-cement or wood composite. These products all require painting or staining when installed (though some come factory-painted) as well as regular maintenance painting every ten or twenty years. Vinyl or aluminum siding mimics the look of clapboards without requiring painting. (Both can be painted though, if you want to change the look.) Stucco and brick or stone veneer are also forms of siding.

Between the siding and the sheathing will be the weather resistive barrier (WRB), composed of tar paper or newer house wrap materials such as Tyvek. The WRB is crucial because all siding materials can leak, leading to issues such as rot or mold growth. Integrated with windows and doors using adhesive flashing tapes, the WRB is what really keeps exterior water out of the house. Some new sheathings have an integral WRB, saving a step during construction.

Stay Warm

Inside exterior walls, at least in newer houses, will be insulation. Unless they’ve been retrofitted, most houses built before the 1950s won’t have wall insulation. The most common insulation is fiberglass, but cellulose, spray-foam, and mineral wool are also found. Insulation is important in warm climates as well as cold.

Increasingly stringent energy codes are increasing the number of houses that have a layer of exterior insulation, usually of rigid foam, but sometimes of mineral wool or cellulose panels.

It’s What’s Inside that Counts

The inside surface of walls is usually covered with drywall, commonly called Sheetrock, which is in fact a proprietary brand name. Older homes and high-end new homes will have plaster instead of drywall. Harder and more durable, plaster is also more expensive to install. In old homes, plaster is a three-coat system applied over wood or metal lath. In new homes, it’s usually a single coat applied over blueboard, a special type of drywall.

Using decorative wall finishes such as ornate wainscot moldings; shiplap, beadboard, and nickel-gap paneling, as well as wallpaper is a great way to create an accent wall. All can be applied over drywall or plaster. Of course, a great way to change the look of any room is to update the paint color of the walls.

Plaster and drywall occasionally crack or have holes knocked in them. In many cases, it’s a relatively simple matter of cleaning out the broken material, applying drywall tape and compound, sanding, and repainting. Sometimes though, a new piece of drywall is needed. This can be a DIY project but expect it to take patience and produce dust. Cracks in plaster can be repaired with patching compounds, as long as the underlying plaster is still sound. If an area of plaster is loose, it’s probably best to call in a pro.

It can be tempting to move or tear out an interior wall as part of a remodeling project. In fact, most interior walls are not load bearing, with the most common exception being central walls that run parallel with the ridge of the house’s roof. These often carry the weight of floors and ceilings down to a main beam in the basement or crawlspace. Even this is not a given, so you should consult with a pro before undertaking any project that involves moving or taking out a wall. If it is a bearing wall, removing it is for the pros.

Other considerations include the utilities that run behind the drywall. Wiring can be relatively simple to move, but plumbing is often more difficult. Perhaps surprisingly, duct work can be the most difficult hidden utility. All three of these usually call for a pro.