But really now, what about that fastener?
What should we make of the fastener in the original picture? It's overdriven through OSB sheathing (which is wood-based, kind of like plywood, but less expensive and more moisture sensitive) that is coated in the factory with a membrane that controls water and air. The manufacturer of the product (Huber) recommends that these fasteners are installed such that their heads are flush with the exterior surface, and also that sealant is applied over any that are overdriven. Pretty standard stuff. And you should follow their advice.
But what if you didn't seal all the fasteners through your sheathing? Not just what if you didn't, what if you couldn't?
Well, the bad news for you fastener alarmists is that while you can do a pretty good job of policing the installation of the fasteners that hold the sheathing in place, you often cannot see -- never mind seal -- the fasteners that hold the cladding in place.
I should pause here to note that this is not always true. You could apply sealant over all of your brick ties (I don't think you should, but you could) or you could use a cladding system that is glued onto the sheathing rather than one that is mechanically fastened, but many of the most popular cladding systems (lapped siding, panel systems, stucco, brick, stone) require thousands of fasteners through the sheathing, and those fasteners never get sealed, no matter what you're using as your water and air control membrane.
Do we care? Yes! But sealing those pathways is not the only approach to water control, and it's often not the most effective approach. Source control, reducing hydrostatic pressure, including a capillary break, and providing drainage and drying are all more important -- and more effective -- than sealing these pathways.
But how do you do all these things? By providing a drained and back vented cladding with either an air space, a textured building wrap, or a drainage mat depending on the cladding type and your preferences related to installation. There are tons of manufacturers that will be happy to provide a solution here. You like Cosella-Dorken? Go for it! Got your eye on Benjamin Obdyke? Enjoy! You dig those cowboys over at Tamlyn? Giddy up! All of them will sell you a drainage mat or mesh for your above-grade walls. DuPont has even gotten in the game with their DrainVent product. You could also cut your own furring strips out of sheets of XPS. Or go old school with classic wood. Cor-A-Vent makes some nice plastic furring strips that you can run vertically or horizontally to accommodate different cladding fastening patterns.
Providing a gap for drainage and drying behind your cladding really is the easiest, least expensive, and most effective way of reducing the risk of water related failures in your wall assemblies. This is a design issue more than a product issue.
So! Why, specifically, are we not concerned about overdriven fasteners with drained and back vented claddings?
1. Because with the cladding installed not much water will reach the penetration (i.e. there is source control).
2. Because the pathway to the interior is very small.
3. Because both the cladding and the air space in front of the fastener greatly reduce the driving forces (wind, capillarity, hydrostatic pressure) and the air space provides drying.
4. Because we know from first principles and industry experience that this design approach is reliable.
We know that a little bit of water will indeed reach these unsealed fasteners. The sheathing might even swell up a bit around them and we might also see a bit of corrosion on the fastener. This will happen at the fasteners that hold the sheathing in place and the fasteners that hold the cladding in place. But when the cladding is properly drained and ventilated none of this is a problem.
But even if it's not a "problem" wouldn't it still be better to avoid this by using a water control membrane that's more "self-sealing" around the fasteners? No. While self-adhered and fluid membranes are often understood to have the ability to seal these types of pathways better, there is no commercially available water control membrane that is sufficiently self-sealing to resist hydrostatic pressure. Not one. Providing a small space for drainage and drying is mandatory in drained walls, regardless of the type of water control membrane.
This is not to say that there is no value in self-adhered and fluid membranes, though! These membranes are often more durable, provide superior airtightness, and are more intuitive to detail than either mechanically attached or integral membranes.
Next: What about Structure?
But what if you didn't seal all the fasteners through your sheathing? Not just what if you didn't, what if you couldn't?
Well, the bad news for you fastener alarmists is that while you can do a pretty good job of policing the installation of the fasteners that hold the sheathing in place, you often cannot see -- never mind seal -- the fasteners that hold the cladding in place.
I should pause here to note that this is not always true. You could apply sealant over all of your brick ties (I don't think you should, but you could) or you could use a cladding system that is glued onto the sheathing rather than one that is mechanically fastened, but many of the most popular cladding systems (lapped siding, panel systems, stucco, brick, stone) require thousands of fasteners through the sheathing, and those fasteners never get sealed, no matter what you're using as your water and air control membrane.
Do we care? Yes! But sealing those pathways is not the only approach to water control, and it's often not the most effective approach. Source control, reducing hydrostatic pressure, including a capillary break, and providing drainage and drying are all more important -- and more effective -- than sealing these pathways.
But how do you do all these things? By providing a drained and back vented cladding with either an air space, a textured building wrap, or a drainage mat depending on the cladding type and your preferences related to installation. There are tons of manufacturers that will be happy to provide a solution here. You like Cosella-Dorken? Go for it! Got your eye on Benjamin Obdyke? Enjoy! You dig those cowboys over at Tamlyn? Giddy up! All of them will sell you a drainage mat or mesh for your above-grade walls. DuPont has even gotten in the game with their DrainVent product. You could also cut your own furring strips out of sheets of XPS. Or go old school with classic wood. Cor-A-Vent makes some nice plastic furring strips that you can run vertically or horizontally to accommodate different cladding fastening patterns.
Providing a gap for drainage and drying behind your cladding really is the easiest, least expensive, and most effective way of reducing the risk of water related failures in your wall assemblies. This is a design issue more than a product issue.
So! Why, specifically, are we not concerned about overdriven fasteners with drained and back vented claddings?
1. Because with the cladding installed not much water will reach the penetration (i.e. there is source control).
2. Because the pathway to the interior is very small.
3. Because both the cladding and the air space in front of the fastener greatly reduce the driving forces (wind, capillarity, hydrostatic pressure) and the air space provides drying.
4. Because we know from first principles and industry experience that this design approach is reliable.
We know that a little bit of water will indeed reach these unsealed fasteners. The sheathing might even swell up a bit around them and we might also see a bit of corrosion on the fastener. This will happen at the fasteners that hold the sheathing in place and the fasteners that hold the cladding in place. But when the cladding is properly drained and ventilated none of this is a problem.
But even if it's not a "problem" wouldn't it still be better to avoid this by using a water control membrane that's more "self-sealing" around the fasteners? No. While self-adhered and fluid membranes are often understood to have the ability to seal these types of pathways better, there is no commercially available water control membrane that is sufficiently self-sealing to resist hydrostatic pressure. Not one. Providing a small space for drainage and drying is mandatory in drained walls, regardless of the type of water control membrane.
This is not to say that there is no value in self-adhered and fluid membranes, though! These membranes are often more durable, provide superior airtightness, and are more intuitive to detail than either mechanically attached or integral membranes.
Next: What about Structure?