Special connections for engineered wood

By Tom Evans Simpson Strong-Tie

ETNGINEERED wood is becoming more popular every I-rdav. With it comes the benefits of stable dimensions and consistent quality. By now, most framers are over-thehump on the installation learning curve, one of engineered wood's biggest challenges. However, here are a few pieces of information that you may find useful when helping builders decide how to make the proper connection.

LVLISCL Connections

When supplying multiple plies of engineered structural composite lumber such as LVL or TimberStrand, the manufacturer usually provides some guidance on assembly regarding nails, nail spacing, and allowable loads. The basic approach is that each member should carry an equal share of the applied load. Therefore, a 3-p1y beam must have enough fasteners to transfer two-thirds of the load from the outside loaded ply to the next two plies. Then, in turn, there must be enough fasteners to transfer the remaining third of the load to the last ply.

By now, most framers are over-

the-hump on the installation learning curve,

The manufacturer's literature usually assumes a uniform load. For common beam and header sizes, incidental concentrated loads of a few hundred pounds applied to the side of the assembly are not a concern. The time to pay extra attention is when there is a heavy concentrated load being applied to the side of a multiple-ply member. In such cases, using some additional fasteners on both sides of the assembly in the vicinity of the heavy load is recommended. For example, if you have a heavy-duty top flange hanger hanging on the side of a triple LVL. In this case, use the two-third/one-third load scheme described above.

A 4-ply assembled beam usually requires bolting. A simpler way to get the job done is to use specialty fasteners such as Simpson Strong-Tie's SDS Strong-Drive wood screws. Be sure to start the screw pattern so that it doesn't interfere with hanger installations.

I-Joist Connections

When making joisrto-joist connections or hanging connections (such as sprinklers), it's best to get the load into the web. For loads of up to roughly 200 lbs., connections to the flange are typically not a problem. The flange will transfer the load to the web throush the web/flanse con- nection. For larger loads don't connect to the flange. For large loads, instead of connecting to the flange, install backer blocks to both sides ofthe web. A backer block is a wood web filler usually made from plywood or OSB and is the same thickness as the space left on the side of the Ijoist. Most manufacturers will provide specific instructions for installation. However, a good ballpark rule is to attach the backer block with a lOd nail for every 100 lbs. of load, and then clinch on the back side.

When supporting one I-joist from another with a top flange hanger, install blocks tight to the top flange of the carrying I-joist. For a face mount hanger, manufacturers prefer backer blocks be installed toward the bottom flange. Use a backer block on both sides of the l-joist. Install them tight to the top flange and leave a slight gap between the bottom top flange and the backer blocks.