The ‘hows’ of building a wall

Building a wall is but one of many tasks involved with the construction of a room addition or an extensive remodel. Knowing a few “whys” and “hows” about the assembly can simplify the process and eliminate a lot of heartache.

A few wall rules:

•An exterior wall should be built directly over some sort of foundation. The new foundation should match what you already have (assuming you have a proper foundation). If your existing foundation has piers, then so should the new one.

The idea here is that you want your new and old foundations to react to natural movement of the earth below in an identical fashion. It is always wise to have an engineer involved when it comes to the foundation.

•Any wall (interior or exterior) that will be supporting weight (a floor above or a roof) must be itself supported by either a foundation or very sturdy floor members of its own. When a wall runs parallel to the floor, framing members above it is usually known as “nonbearing” (not structural). Framing members that lay atop a wall (ceiling, floor above, roof rafters, etc.) place a “load” (weight from other parts of the structure) on that wall and it is therefore known as a “load bearing” or “bearing wall.” Load-bearing walls must be built in accordance with many rules. Nonload-bearing walls can be built following almost no rules.

•It is a good practice to frame a wall so that the studs are spaced 16 inches apart. Walls that don’t carry a load can use stud spacing up to 24 inches on center. This wider stud spacing represents a very small amount of cost savings but renders a very flimsy end result. We don’t feel it is worth the savings.

•When possible, it is better to construct a wall using two-by-six studs rather than two-by-fours. Besides being more energy-efficient (more room for insulation), a two-by-six wall is superior in several other ways – less vibration and movement in the wind, less sound transference, better load carrying capacity. When extending the length of a wall, the same width studs must be used. This is one case where moving up to a thicker wall is not recommended.

There are only a few elements that make up a basic wall:

•The “bottom plate” is the continuous piece that travels horizontally along the bottom of the wall. When the bottom plate lies on concrete, it must be pressure-treated.

•The “top plate” is the continuous piece that travels horizontally along the top of the wall. There are usually two top plates. The top plate is doubled to add strength and rigidity to the top of the wall. It is not needed at the bottom where the wall is connected to the floor.

•The “studs” are the vertical pieces that extend from bottom to top. The stud should always be a single piece of wood that travels from plate to plate.

Door and window openings must be constructed following certain rules:

•A solid piece of timber known as a “header” must be used to carry the load across any space where studs are removed to accommodate an opening.

•A header is usually the same thickness as the wall and at least one inch high for each foot of opening width. For example: For a common 4-foot opening in a tow-by-four wall, a four-by-four header would be needed, 4 inches for the width of the wall and 1inch high for each of the 4 feet of opening width.

Most contractors use four-by-12 as their standard header because it meets the load requirements for more than 95 percent of all openings and because when it is installed immediately beneath the top plate it comes down to 6 feet, 10 inches high, which is the top of the opening height used for most doors and windows.

•Headers are cut a few inches longer than the opening width so that one or two studs can be placed under each end of the header for support. In construction there must something underneath everything above. For example: An opening for a 3-foot window would need a 3-foot-3-inch header – 3 feet for the window and 1 1/2 inches on either end for a stud. Longer headers need two studs under each end.

There are rules about how many nails must be used in each location to ensure proper wall strength. However, equally important is that when pieces of the puzzle are joined, it is imperative that they be sandwiched tightly together. Just nailing a connection is not enough. There must be no space between connections.

For more home improvement tips and information, visit our Web site at www.onthehouse.com or call our listener hot line at (800) 737-2474.