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Foundation Anchors and Shear Wall Strapping


Traditional anchor bolts are still used to secure the 2×6 interior walls of this Kirkland home to the concrete floor. The mudsill anchor is installed at the time of the concrete foundation pour. Depending on the application, the foundation anchors are spaced 3 to 6 feet apart. One end of the bracket penetrates the wet concrete foundation at an angle. When the concrete hardens, the framing crew lays down the treated wood sill plate. Visible in the photo just below the sill plate is a layer of  1/4″ white foam. This is a sill seal that reduces airflow under the framed wall and makes the home more energy efficient and helps the home pass the required blower door testing. It also serves as a barrier to pests and insects entering the home and reduces moisture infiltration.

Another important structural fastener system is the shear wall strapping or hold downs. 

When the applied force at the top of the wall reaches a certain amount, the overturning moment will equal the resisting moment. Even the slightest additional applied force will cause the wall to turn over. Since we cannot allow walls to overturn, we must install anchors to hold them down to the structural elements below. The word "hold-down" (hyphenated or as one word) highlights the purpose. In some cases even where the overturning moment does not equal the resisting moment, hold-downs are required. Hold-downs can take many forms. Some look like straps that emerge from the foundation and nail to the edge or face of a stud. Others connect foundation bolts or threaded rods to the studs via bolts or nails. The hold-down creates a path for forces to travel out of a shear wall and into other portions of the building.,/div>