By Beverly Smirnis with special thanks to input by Allison A. Bailes III, PhD and Zero Energy Homes Designer, Consultant & Instructor Armando Cobo
With the recent weather events happening all over our country and Texas leading the way in storm incidents this year, we can expect that more home resiliency requirements are coming in the new codes.
This is Part 2 of our 4-part Building Science Section: THE ENVELOPE—PLEASE!
Part 1:
Airtightness and Keeping it Dry are Goals #1 & #2
Part 2:
Making Houses Less Prone to Damage in a Natural Disaster is Goal #3
Part 3:
Fewer Components, Less Waste is Goal #4
Part 4:
Right-Sizing the HVAC is Goal #5
Every building code cycle increases the requirement for walls. New homes are better equipped to resist wind pressures and wall-racking forces and provide better weather protection.
One of the weakest links in residential structures is the connection between the gable end and the wall below. Under high wind loads, the roof-to-wall connection subject to uplift. It’s also subject to shear due to positive or negative wind pressure on the walls below.
Thus, it is essential to tie gable-end walls back to the structure. For the roof-framing-to-wall connection, hurricane/seismic framing anchors or equivalent connectors should be attached on the exterior (sheathing side) of the exterior walls, advises The American Plywood Association (APA).
APA offers data on the most effective way to provide lateral and uplift load continuity. It advises attaching adjacent wall sheathing panels to common framing. Staples offer less resistance to blow-off than nails. This means a greater number of staples are required to achieve the same level of resistance.
Enhanced Nailing Techniques Improve Resistance to Negative Wind Pressure
APA advises nailing upper-story sheathing and lower-story sheathing into common wood structural panel Rim Board. APA also recommends nailing wall sheathing with 8d common (0.131 in. x 2-1/2 in.) nails at 4 inches on center at end and edges of wood structural panels and 6 inches on center along intermediate framing.
The connection of the wall sheathing panel to the sill plate is important because this is where uplift forces are transferred into the sill plate and into the foundation through the anchor bolts. APA says to space ½-inch anchor bolts 32 inches to 48 inches on center with 0.229-in. x 3-in. x 3-in. square plate washers.
Non-Wood Solutions
Concern for fires and windstorm events have insurers rethinking their risks. There’s also the fact that home insurers are substantially raising rates or pulling out of Texas entirely. This has some builders looking at non-wood, non-combustible solutions that are compliant with the International Building Code (IBC) and International Residential Code (IRC).