the line away from the line. Eye down the wall to ensure the face plane is smooth and the perps are lined up vertically. Finally we need to consider the finishing of the wall. The bed and perp joints need to be tooled or ironed in order to satisfy two requirements: to produce the desired appearance that is specified to weatherproof the joint in order to prevent the entry of moisture. The most commonly used joint is called a half-round joint. A specific tool called a jointer is used to produce a concave finish to the mortar just before it begins to harden. The timing of the operation is very important since if its performed too soon it will lead to a rough finish and if its performed too late a black deposit will sometimes form due to what is known as lime burn. Because the profile of the half-round joint is concave, the procedure of jointing pushes the mortar tight against the arris of the brick and seals it against moisture penetration. Its good practice to joint all the perps first, followed by the bed joints. This reduces the number of small projections where the perp joint and the bed joint intersect.

Modifying parts or processes Changing to a different, less noisy process The most common sound control measures usually involve acoustical treatment to absorb sound; but equally important are: Use of barriers to prevent airborne sound transmission Interruption of the path with carefully designed discontinuities Use of damping materials to minimize radiation from surfaces Another important approach involves reinforcing the direct sound with controlled reflections from properly designed reflective surfaces. Often, the most simple and effective approach involves protecting the receivers, enclosing them within adequate barriers, or equipping them with personal protection devices (ear plugs or muffs), rather than trying to enclose or modify huge sources or an entire room or building. TABLE 11.34 Available Options in Noise Control Objectives of sound-control efforts Sound-control procedures* Quiet the source Barrier or enclosures Vibration isolation or damping Absorption Masking

Parallel-Chord Trusses. Spans of 100 ft or more are possible with chords and webs of solid-sawn lumber or glulam timbers. Parallel-chord trusses are commonly used in floor systems and long-span commercial roofs. Advantages for this type of truss include ease of installation, relatively long spans, flexibility for installation of ductwork, plumbing, and electrical wiring, and overall economics. Triangular and Scissor Trusses. Spans of 100 ft or more are possible with chords and webs of solid-sawn lumber or glulam timbers. These trusses are used extensively in residential roof construction and long-span applications in commercial roofs. Advantages are the same as those described above for parallel-chord trusses. Truss Joints. Connectors used in truss joints include bolts, split rings, timber rivets, shear plates, lag screws, and metal connector plates, as described in Art. 10.22.1. The type of connector used depends on the type and size of wood truss components, loads to be transferred, fabrication capabilities, and aesthetics. Lag screws, bolts, timber rivets, and shear plates are suitable for field fabrication, whereas metal connector plates are almost always installed in a truss assembly