Foundation, Structural Framing

Girders (the main support beams) are often supported at both ends by the foundation wall. If the girder is wood-constructed, the notch in the foundation wall in which the girder rests should be large enough to allow the sides and end of the girder to be ventilated. Otherwise, there can be a moisture buildup, which will promote decay. There should normally be at least a ¹⁄2-inch clearance around the sides and end of the girder. For adequate support, there should be a minimum of a 3-inch end bearing in the foundation notch. (See FIG. 11-3.)

If you find that the end of the girder has deteriorated so that it is no longer providing adequate support, do not be overly concerned. The condition can be corrected at a reasonable cost without replacing the girder. In many cases, all that is needed is to support the girder by a column or pier located near the foundation wall. This repair, however, should be performed by a professional, since the column or pier must have an adequate size footing to spread the load.

When girders or joists have sagging sections, these are usually noticeable on the floors above. During your interior inspection, if you find floors that are not level, you should be alerted to the possibility of sagging support beams. Sagging sections can be braced with adjustable screw-type columns to prevent further sag. The adjustable columns can be used for releveling sagging sections. This procedure, however, should be approached with caution. The leveling process introduces new stresses that in turn can cause cracking.

During the wood-framing inspection, you might find joists or girders that have been notched at the top or bottom to accommodate the passage of pipes. Notching a beam at the top or bottom will reduce its strength. Just as a chain is as strong as its weakest link, a beam is as strong as its narrowest section. For example, if a 2-by-8-inch joist is notched to a depth of 2 inches, its strength will be reduced to that of a 2-by-6-inch joist. When a beam deflects, the top of the beam is in compression and the bottom is in tension. At a point approximately midway between the depth, the stresses change from one to the other so that at this point there is no compression or tension. Consequently, if a hole is cut midway between the top and bottom of a beam (as long as the hole is less than one-fourth the depth), there will be no effective reduction in strength. (See FIG. 11-4.) Using the above example, if a 2-by-8inch joist has a 2-inch hole in its center, it will still be as strong as it was without the hole. If you find any notched beams, look specifically for signs of excessive deflection. This is an indication that reinforcement or bracing of the beam is necessary.

Most building codes require cross or solid bridging between the floor joists. (See FIG. 11-5). The purpose of bridging is to hold the joists in a vertical position and to transfer the floor load from one joist to another. Cross bridging consists of pieces of wood or steel set in a diagonal position between the joists to form an X. Solid bridging consists of solid blocks set between the joists. While inspecting the overhead floor joists for rot, insect damage, notching, and sagging sections, you should also check for the presence of bridging. If it is missing, record the fact on your worksheet for later installation.

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