The skeleton or frame of a house is mostly hidden by other building materials, but it is sometimes important to know exactly where pieces of the frame–the wall studs and floor-ceiling joists–are located.
For example, locating studs is important when a heavy object needs to be attached to a wall (only studs, not wall coverings, can support heavy loads), or when a partition or new wall is to be built. Locating joists is important when loose, squeaking floorboards need to be refastened, or a ceiling light or ceiling fan is being installed.
When one stud or joist is found, it is usually easy to find others because framing members are usually installed 16 inches apart, from the center of the board. Measuring 16 inches right or left from one stud should locate another one.
There are exceptions, however. Some houses are built with framing members 24 inches apart, and some older houses have spacing that is slightly erratic.
A clue to the direction in which joists run in a house can often be found in the basement or attic, where joists are often visible. Hidden joists generally run in the same direction as the visible ones.
A high-tech method for finding pieces of hidden frame is to use an electronic stud finder, but there are also several low-tech, low-expense methods that do-it-yourselfers can use. A combination of methods might also be needed to pinpoint framing members. Following is a digest of the various methods:
– Electronic and magnetic stud finders. Electronic stud finders, such as the StudSensor Pro (about $37) and TriScanner (about $35), both by Zircon (800-245-9265), work by detecting the extra mass of studs and joists inside hollow walls and ceilings. These pocket-size tools are sold at some home centers or can be bought by mail from tool dealers such as Woodworker’s Supply, Casper, Wyo. (800-645-9292). Electronic finders, which use a light or tone as a signal, are a fast and accurate method for detecting studs and joists, but the cost will deter many do-it-yourselfers. A magnetic stud finder, which costs about $3, works on a different principle. This tool has a small, movable magnet that reacts when the tool is passed over a hidden nail. Look for rows of nails, rather than a single nail, to indicate the presence of a stud or joist.
– Knocking. This is the lowest of low-tech methods, but it can help pinpoint the general location of framing. Knocking or thumping on the wall, ceiling or floor with knuckles will yield a “hollow” sound between framing members and a “solid” sound over a stud or joist.
– Electrical clues. Electrical switches and outlets are generally attached to studs, and very frequently to the right side, since most nailing is right-handed. Knocking can be used to help verify which side of the stud the box is on.
– Heating and air-conditioning outlets. These are between studs or joists. Again, use knocking to help verify the frame’s location.
– Shine a light. Darken the room, and hold a flashlight so the beam shines close to and parallel to a wall or ceiling. Shadowy dimples in the surface indicate the presence of hidden nails that were used to attach wallboard to the frame. The light-shadow pattern will sometimes also make framing stand out like ribs.
– Check the baseboard. Baseboard trim is often nailed to studs, and nail locations are sometimes visible as small dimples on the surface of the wood. Carefully removing a section of baseboard can also reveal nails or wallboard joints that indicate the presence of a stud.
– Drilling. This is a good way to definitely locate or verify the presence of a framing member, and should be used in conjunction with one or more of the tests described above. If the drill bit strikes solid wood immediately behind wallboard or other covering, a framing member has been located. If the bit penetrates to a hollow space, move it laterally an inch or two and try again. Do not drill in areas where plumbing pipes or electrical wiring might be located inside walls (in the vicinity of plumbing and electrical fixtures). Use an electric drill with a very small bit (1/16- or 1/32-inch in diameter).
Once a framing member has been located, use a level, plumb bob or carpenter’s square to map its course through the wall, ceiling or floor. For example, studs should be vertically plumb, so if one is found by drilling near the floor, a plumb bob (a string with a weight on the end) or level can be held over the hole to trace where the stud is at a higher point.
