An expert engineer in wood structures identifies the most common framing mistakes and offers advice on how to avoid them.
Sometimes it’s the simple things that can make the difference between quality construction and satisfied customers and the home construction that dogs you with callbacks and complaints.
The typical errors that we see in the field are both common and highly preventable. Reducing callbacks is all about paying attention to detail and keeping up with wood construction systems that deliver the best structural and building science performance. While home construction isn’t a field that is usually known for its technological advancements, there are, in fact, important developments in building materials and systems that significantly improve both the building’s performance and the buyer’s satisfaction with the home.
The top 10 list of common framing errors includes:
New Plate Washer Requirements for Engineered Shear Walls
New provisions in the 2009 and 2012 International Building Code will require the use of plate washers on most sill plate anchor bolts in engineered structures, such as multi-family and commercial projects, as well as one- and two-family homes designed using the IBC.
Although builders in high-seismic regions have been using plate washers since the late 1990s to improve the performance of wood shear walls, this requirement will be new for most low-seismic regions, according to Shane Vilasineekul, P.E., branch engineering manager with Simpson Strong-Tie. Vilasineekul offers a few important details to keep in mind:
- The purpose of the new requirement is to limit the tendency for sill plates to split length wise between the anchor bolts. This can occur when anchor bolts are supporting the center of the sill plate while the sheathing pulls up on the edge of the sill plate, creating a prying action.
- The new plate washer requirements apply to shear walls designed under the IBC. There are no changes to the plate washer provisions prescribed in the International Residential Code, which only requires plate washers in high-seismic regions or when designing for extreme winds.
- The plate washer must be a minimum 3 x 3 x 0.229 inches (3 gauge) and extend to within ½-inch of the sheathed edge of the sill plate.
- To allow for larger tolerances in anchor bolt placement, the code permits the plate washer to be slotted when a standard cut washer is used.
- New, slotted plate washers that are 4½-inch wide can be used for 2x6 framing that is sheathed on both sides or for anchor bolts centered in 2x6 framing that is sheathed on just one side.
There are five framing principles that are the basis for preventing these common errors:
This last principle is a big one. While wood-frame construction makes it easy for builders to construct strong, durable buildings, wall studs alone can’t withstand high wind and seismic forces. A continuous load path safely transfers the lateral, vertical, and racking loads caused by severe weather and earthquakes from the roof, wall, and floor systems to the foundation. The continuous load path is achieved by connecting the structural frame, wood structural panel sheathing, and fasteners together. The result is like a chain that ties the house together from the roof to the foundation. If any link in the chain breaks, the overall structural system could weaken. If each link is strong enough to handle the applied loads, however, a continuous load path will provide tremendous resistance against the forces of nature.
Wall bracing is one of the most important structural elements of any house, but it can also be one of the most confusing. Wood structural panel sheathing is the easiest and most economical way to meet International Residential Code prescriptive bracing requirements. Continuous sheathing with wood structural panels provides superior bracing to resist uplift loads, lateral loads, and wind pressures while providing a secure connection to the roof and protecting the occupants. Additionally, wood structural panel sheathing provides impact resistance from storm-blown objects and holds fasteners securely for siding application.
Fasteners are the final link in the chain, and the effectiveness of the structural system relies on the quality and quantity of the connections. In hurricanes, the loss of roofing materials and sheathing is the leading cause of structural failure in wood-framed buildings. The central reasons behind these failures are improper connection detailing between structural systems and inadequate fastening of sheathing to supporting members. Understanding connection detailing and adhering to a prescribed fastener schedule is critical to completing the load path.
By adhering to these framing principles, paying attention to details, and maintaining a commitment to understanding wood frame systems, builders can reduce callbacks, satisfy homeowners, and increase profits.
Founded in 1933, APA represents approximately160 plywood, oriented strand board, glulam timber, wood I-joist, rim board, and laminated veneer lumber mills throughout the U.S. and Canada. Its primary functions are quality auditing and testing, applied research, and market support and development.