All too often we find ourselves repairing exterior walls because of water infiltration. Our goal here is to educate you about why this happens and what you can do to prevent it from happening to you.
If you apply some proactive intelligence to the stewardship of your home you too can avoid showing up on our page of repair projects! Please, please take this to heart! We want to save you stress and dough; we want to help the environment by avoiding having to replace building materials well before the end of their potential, useful life.
Step one is to read this two page article entitled ‘Introduction to Modern Building Techniques’ written by our guru in building science, Joseph Lstiburek, PhD., P.Eng.; www.buildingscience.com. If you read but one piece about building science, this should be the one!
Most people believe that paint, siding, exterior trim and especially caulking, prevent water and wind from reaching the sheathing, framing and insulation within. While theoretically true, realistically it’s not. Don’t just take our word for it; look at the repair projects we’ve worked on!
Water wins; it’s that simple. And if water does make it into the wall assembly, rot and mold happen. So here’s the logic we embrace and acknowledge: since water does make it through a building’s ‘skin’, build the exterior wall assembly so that there’s a way out for the water… get it out and allow the building materials to dry out.
Patrick’s input after reading the study ‘Evaluating Drainage Characteristics of Weather Resistant Barriers as Part of an Overall Durable Wall Approach for the Building Enclosure’ by Mark F. Williams…
“… it is very clear that we should never be using tar paper (also called building paper) or non-drainage enhanced housewrap like standard Tyvek. (Tyvek’s drainage-enhanced housewrap is simply a ‘roughed up’, crinkly version of standard Tyvek, and this added dimension holds the siding away from the wall surface just enough to allow some amount of enhanced drainage. And the added expense for this additional drainage is minimal!)
“Instead we should be using a drainage-enhanced building wrap like Tyvek’s ‘DrainWrap’ and, where possible, incorporate a drainage space created by furring strips placed behind the siding. Sure, these strategies are more costly… but not by much; I consider it inexpensive insurance!
“In the study, performance is rated by the speed at which water first appears coming out of the wall assembly, and how much of the introduced water actually makes it out. The drainage-enhanced building wrap, along with a drainage space, is clearly the assembly of choice.
“Another interesting factor is the relationship of the siding materials and the framing. Apparently framing materials give up moisture much, much more slowly than sheathing and siding materials, especially when there is no drainage space…as much as 100 times more slowly! So keeping the two as separate as possible makes sense…also getting as much water out as quickly as possible. This minimizes the chance for water to make it to the sheathing layer through small penetrations or fasteners; this is critical as well.
“In a nutshell… pushing people who want to use conventional cladding/siding towards a ventilated wall system is the responsible thing to be doing if our mutual goals are long life span and minimal maintenance. I think it should become our norm for new work and, whenever practical, for repairs and resides.”
Patrick is right on, but there are two reasons that might prevent the inclusion of a drainage plane.
Furring a wall out for this additional space between the siding and sheathing creates a thicker wall. Not a problem when we’re dealing with an entire wall. But what if the repair work only affects half of that wall? If we added the drainage plane to only half of the wall then the two halves of the wall would have different thicknesses! Hard to side over this problem, don’t you think? So we must either forgo the drainage plane or else strip off the rest of the siding so as to fur it out in its entirely.
The other reason to forgo the drainage plane is to save a few dollars. Given the discussion above; given the results we’ve seen in the field… fight this one! This is not the place to save dough! HERE is but one of the stories, amidst dozens of them, why this is o important. There is hardly any insurance imaginable that is more important than optimizing the drainage performance of your exterior walls. Just do it!
This is why we spend so much training time on learning how to do this correctly. All of our production people are drilled on doing this right the first time. Yet if you ask ten carpenters to define what’s ‘right’, you’ll get ten answers.
After extensive research we’ve settled upon DuPont’s Flashing Systems as our definition of ‘right’. Go HERE in order to study how Dupont helps us get the job done right. (It must be true; it says so right on the front page!)