Some people (mostly folks who live in big cities!) think that builders who live in small towns are behind the curve when it comes to technology and better building practices. But the truth is that every state in the U.S. is actively improving building codes, and through new requirements on everything from decks to framing to air infiltration to housewrap, even small towns in America are getting up to speed.
Here in Oregon we have a unique code requirement when it comes to housewrap. Officials in our state have recognized what everyone has known for years—sandwiching plastic housewrap tightly between OSB sheathing and siding is a recipe for disaster!
Because of pressure differentials—like high-pressure wind blowing rain against the siding—moisture will always penetrate siding and be drawn toward areas where there is lower pressure, like the housewrap behind the siding. That’s why siding is called the “PRIMARY“ weather barrier.
And most of the siding products we use, like wood, fiber cement, and OSB, absorb moisture, and sometimes a lot of moisture. That’s why they’re called reservoir claddings. Without a gap of some kind to help that moisture dry out (building scientists call that process diffusion), that moisture works its way through the housewrap, into the sheathing, and…well, you all know that story.
In Oregon, we now have a new code requirement for housewrap—a 75% drainage rate requirement. Now I don’t know what the percentages really mean, but I do know that a drainage rate is a measure of how quickly a specific housewrap drains.
To meet this new code requirement, we’re starting to see new drain wrap products even in my little town in Southern Oregon. Recently, I installed some HydroGap. Because of the five-foot tall rolls, I found it easier to install than the other wraps I’ve used in the past. And hey, if it helps the trim and siding last longer on my jobs and keeps the wall cavities of my customers’ homes dry, I’m all over it.