William Costello is building a new house in southwest Virginia that will be framed with 2x6s and will include up to 2 inches of exterior rigid foam insulation. He plans on installing 3/4-inch thick plywood furring strips on top of the exterior foam, and then will side the house with LP SmartSide lap siding designed specifically for houses with 24-inch on-center framing.
It all sounded straightforward enough until Costello took a close look at the installation instructions from LP Building Products.
“I discovered that LP’s installation instructions specify 1.5-inch by 3.5-inch furring strips for foam greater than 1 inch in thickness,” Costello explains in a Q&A post. “So I guess that would basically mean a 2×4 stud for every 2×6 stud in the wall. This is more material and expense than we had bargained for, and perhaps also more increase in wall thickness than we want for window installation.”
He double-checked with LP to make sure that’s what would be required to maintain his warranty, and indeed that’s the requirement. There’s a chance he could keep the thinner furring strips if he used fasteners for the siding that were long enough to bite into the 2×6 framing, a rep told him, but he’d need written approval. That would leave him with buying more expensive fasteners, so the option isn’t necessarily very appealing.
Costello sees several options: install the siding according to LP specs; install it his way and hopes he never has to make a warranty claim; use 1 inch of polyiso insulation instead of the 1 1/2-inch to 2-inch EPS and forget the vented rainscreen; or use extra long fasteners for the siding.
What’s his best option?
Next time, plan ahead
Costello’s dilemma is a good example of why better planning is important, replies GBA…