Ah, the overdriven fastener!
Here is a helpful sentence: for water infiltration to be problematic, the wetting a wall assembly experiences must exceed its capacity to store and redistribute water for long enough to damage the materials that compose it.
Thinking of building systems in terms of exposure to various kinds of stresses is perhaps the single most useful concept for knowing how to handle risk in building enclosure design. All this talk of “barriers” notwithstanding, our walls, roofs, and windows are almost never blocking water; what they’re doing is managing water (or air, or energy)... with varying degrees of success.
This concept applies to structure and fire, too. We don’t design buildings that never, ever, fall down, or ones that never, ever, burn. We design in such a way that they are capable of standing up to the most common stresses in their environment and we design them to fail, if they fail, in ways that are most likely to minimize loss of life.
We would do well to think of water as a load, and apply the same principles. In the example photographed -- an overdriven fastener -- the moisture load doesn’t even come close to being a problem when the overdriven fastener in question is part of a wall that has a drained and back vented cladding (say, fiber cement panels on furring, or brick with a 2-inch air space). That wall’s capacity to store and redistribute water is great enough to handle it even if literally every single fastener were overdriven.
That said, people seem pretty worked up about this particular issue so let’s get into a little bit more detail, shall we?
Next: Leaks, in general
Thinking of building systems in terms of exposure to various kinds of stresses is perhaps the single most useful concept for knowing how to handle risk in building enclosure design. All this talk of “barriers” notwithstanding, our walls, roofs, and windows are almost never blocking water; what they’re doing is managing water (or air, or energy)... with varying degrees of success.
This concept applies to structure and fire, too. We don’t design buildings that never, ever, fall down, or ones that never, ever, burn. We design in such a way that they are capable of standing up to the most common stresses in their environment and we design them to fail, if they fail, in ways that are most likely to minimize loss of life.
We would do well to think of water as a load, and apply the same principles. In the example photographed -- an overdriven fastener -- the moisture load doesn’t even come close to being a problem when the overdriven fastener in question is part of a wall that has a drained and back vented cladding (say, fiber cement panels on furring, or brick with a 2-inch air space). That wall’s capacity to store and redistribute water is great enough to handle it even if literally every single fastener were overdriven.
That said, people seem pretty worked up about this particular issue so let’s get into a little bit more detail, shall we?
Next: Leaks, in general