Preventing Water Damage Behind Siding
At Yanish, we find water damage behind the siding of roughly 1 in 6 homes. Not all have wood rot, but the damage would progress to rot in time.
Water damage is risky business. It easily hides beneath siding materials and often shows no obvious signs to untrained eyes. The damage can compromise a building’s structural integrity. This is especially true when it leads to wood rot, which welcomes its own unique set of issues. Repair costs rack up quickly, so it’s worth taking preventative measures to ensure your home is as water-resistant as possible.
We’ll discuss the following issues and solutions to water damage in homes:
- Why siding alone doesn’t prevent water damage
- Proper flashing techniques
- The importance of a good house wrap
- Effective caulking
Siding Alone Doesn’t Prevent Water Damage
Yanish uses top quality, breathable vinyl siding to prevent water damage, but we also take additional steps to ensure maximum protection against moisture. The key to creating a water-resistant exterior is proper layering. In terms of siding, this means layering sheeting, flashing, house wrap, caulking, siding, and trim. It’s virtually impossible to completely seal any siding without additional materials.
Vinyl siding itself is waterproof and directs most water flow away from the exterior, but even a small gap can allow water through. The roof and foundation, doors, windows, and any other breaks in siding create opportunities for moisture to seep in. The source can be rainfall (especially wind-blown rain), humidity, or even sprinklers placed near the home.
It only takes a small amount of water to cause damage, and water easily accumulates with each exposure. Without materials in place to combat this issue, it’s only a matter of time before an easy fix becomes an expensive, full-blown repair project.
Proper Flashing Techniques
Siding is designed to direct water away from a home, but flashing helps close the gaps between siding and other materials. Flashing is a thin strip or sheet, usually metal, installed at junctions between exterior surfaces to control water flow. It often borders windows and doors, roofs, chimneys, and thresholds. Flashing is necessary anywhere the direction of a drainage plane changes (i.e. where a patio or deck meets the exterior of a home).
Keep in mind that flashing must be sized and placed appropriately to be effective. Be sure it is high enough and has adequate width to prevent water from overflowing and leaking behind it. Consider factors like wind-blown rain, which effective flashing will accommodate without overflow. Wind-blown rain may also prompt you to install flashing in places that did not initially appear to need it, such as around windows and doors beneath eaves. Flashing should redirect water adequately on its own—don’t rely on caulking to make up for an improper fit.
The Importance of House Wrap
House wrap is another major line of defense against water damage—in fact, water resistance is its primary purpose. It is placed beneath siding to keep water away from sheeting, and it also provides some support in minimizing air infiltration. A good house wrap is highly water-resistant, surfactant-resistant, and overall durable.
Quality house wraps always test their products and offer the results. Check results of water ponding and hydrostatic pressure testing to compare water resistance. As a rule of thumb, it’s best to choose the most water resistant material when comparing similar products. Because house wrap is typically installed with surfactant, it’s important to find a product that is surfactant-resistant as well. If the house wrap quality deteriorates with exposure to surfactant, the material can become less water-resistant—and that defeats the purpose.
Even the most careful, experienced contractors must put some faith into the materials they are using. House wrap should resist tearing and maintain its quality throughout the installation process. If you know or suspect your project will require house wrap to be exposed for more than about a month, be sure UV ray exposure will not compromise the material’s original condition.
Caulking seals small areas where water would otherwise enter. While it may seem reasonable to caulk everything in an attempt to fully seal an exterior, this is counterproductive. Effective caulking seals gaps where water would enter, but gaps that allow moisture to escape should be left open.
Let’s start with where caulking is necessary. Water damage often occurs near corners and edges, and caulking in these places keeps moisture from seeping beneath siding. This also applies to trim boards and wooden window frames. Any inconsistencies in siding, such as cracks, nail holes, and the like, should also be caulked.
Caulking should not be applied to trim boards that sit above the siding, window weep holes, or the bottom of siding. It should be used sparingly—if not at all—around metal flashing and metal-to-wood junctions. These are exit points for water; they allow ventilation for house wrap and sheeting.
For more information, check out our other blog posts: