238 Section 2 Foundations and Framing Built-up girders can be made of three or four pieces of 2″ lumber nailed together with 10d nails. See Figure 10-7. Modern engineered lumber, such as laminated beams, may be used for girders. These are factory-made by gluing together thin strips of wood or veneer. Such beams can be man- ufactured in many different sizes and lengths. Joints should rest over columns or posts. Procedure Sizing Built-Up Girders 1. Determine the number of stories of the building. 2. Find the width of the building. That is, find the distance between exterior walls. 3. Select the proper girder size according to the local building code in your area. Built-up wood girder sizes that comply with the IRC are shown in Figure 10-8. 4. Determine the span of the girder by measuring the distance between columns or piers supporting the girder. 5. If engineered lumber is used, consult the manufacturer’s span table to determine the specifications for girder sizes. 10.2.1 Steel Beams In many localities, steel beams are used instead of wood girders. The W-beam (wide flange) is generally used in residential construc- tion. Common structural steel shapes and their designations are shown in Figure 10-9. Wood beams vary in depth, width, species, and grade. Steel beams vary in depth, width of flange, and weight. Sizes of steel beams depend on the load. Figure 10-10 shows how the load is calculated. After the approximate load on a steel beam has been determined, the correct size can be selected from the manufacturer’s span table, such as the one shown in Figure 10-11. This table lists a selected group of steel beams commonly used in residential structures. For example, if the total, evenly distributed load on the beam is 15,000 lb. and the span between supports is 16′-0″, then a W8 × 18 beam should be used. This specifies an 8″ deep beam weighing 18 lb. per lineal foot. The width of the flange is 5 1/4″. 10.2.2 Posts and Columns For girder and beam support, steel posts are most popular. The post should be capped with a steel plate to provide a good bearing area. A steel post designed specifically for this purpose has a threaded hole at one end. A rod attached to a plate is threaded into this hole. This arrangement allows for adjustment as the wooden beam and other structural members shrink. For wood posts shorter than 9′ , it is safe to assume that a post with its greater dimension equal to the width of the girder it supports will carry the girder load. For example, a 6 × 6 post is suitable for a girder 6″ wide. For a girder 8″ wide, a 6 × 8 or 8 × 8 post should be used. Adequate footings must be provided for girder posts and columns. Wood posts should be supported on footings that extend above the floor level, as shown in Figure 10-12. To make sure the posts will not move off their footings, pieces of 1/2″ diameter reinforcing rod or iron bolts should be embedded into the footings before the concrete sets. They should project about 3″ into holes bored in the bottoms of the posts. A post anchor can be used to securely hold the wood post, Figure 10-13. It supports the bottom of the post above the floor, protecting the wood from dampness. The bracket 4" minimum bearing Girder extends above foundation by the sill thickness Stagger joints and locate over post Post 1/2" Clearance both sides and end Pocket Goodheart-Willcox Publisher Figure 10-7. When built-up wood girders are fabri- cated on the job, nails should be spaced no farther apart than 32″ along the top and bottom edges. A metal bearing plate should be placed under the girder at the foundation wall. Clearance in the pocket allows air circulation and prevents rot from moisture. Copyright Goodheart-Willcox Co., Inc.