The Drainage Debate
Built-in redundancies of water-managed EIFS provide common-sense insurance.Based on generations of experience, builders of brick, siding and traditional stucco systems know that sooner or later, water will penetrate the surface of virtually every home and building exterior, often at windows, other penetrations and roof and wall intersections. They’ve learned that by incorporating weather-resistant barriers, flashing, weeping and other water-management features, exterior systems can handle water when it eventually does penetrate the surface and safely drain it out of the wall before it can cause damage. These types of redundant “belt and suspender” designs are integral to virtually every cladding system used today. The design of water-managed EIFS reflects these long-held building practices.
Anatomy of a systemWater-managed EIFS typically include:
• A weather-resistant barrier that prevents intruding water from reaching moisture-sensitive framing and sheathing.
• Flashing, weeping and special construction details around areas proven to be focal points for water penetration. These areas include windows, doors, wall/deck and roof/wall intersections, pipe and vent penetrations, and dormers.
Some water-managed systems also feature water-durable substrates as backups to the systems’ initial line of defense: the water-resistant polymer basecoat, finish and sealants.
The makers of barrier-type EIFS assume, however, that their systems will stop moisture solely with a watertight surface, so they forego backup measures. They assume that windows, doors and other openings are perfectly sealed and watertight, thus keeping water out for the life of the system.
Unfortunately, no one builds a perfect exterior wall. It is true that water rarely penetrates an unbroken expanse of polymer finish in an EIF system, but buildings are not constructed without windows, doors and other interruptions to that surface. The sealants that bond those interruptions to the EIFS cladding are subject to normal construction defects, naturally occurring aging of the system and delayed maintenance, all of which produce cracks and other damage to the sealants.
These flaws can compromise the integrity of the water-resistant surface, allowing moisture to enter the wall and become trapped inside the system.
The Carolina conundrumBarrier EIFS manufacturers maintain that the problem of trapped moisture and water intrusion lies with applicators, window manufacturers and the failure of building owners to replace aging sealants. Contractor education and training are certainly important—and so is regular and timely maintenance (for no exterior cladding system is maintenance-free). But manufacturers of barrier EIFS should neither rely on contractors’ perfect installation nor on building owners’ perfectly timed maintenance to preserve an EIF system based on a sole line of defense to ensure its integrity. Many members of the building community agree with this point, and nearly all EIFS manufacturers now offer water-managed EIFS as part of their product lines. So what is behind the continued use of barrier EIFS?
Barrier systems can be a viable cladding alternative in very arid climates or for application over water-durable substrates such as concrete and masonry. However, even in dry climates, problems may arise given enough time and occasional wet weather.
Cost competitiveness is one factor that promotes the continued use of barrier EIFS. Water-managed EIFS can cost slightly more per square foot to install, but when building owners understand the long-term insurance that water management brings, they would generally agree that the incremental additional cost is a wise investment. Ease of installation also plays a role. Yes, water-managed systems are more complex, however, ongoing advancements in these systems are making them simpler than ever to install. Moreover, the steps taken to ensure that an EIF system is water managed are no more complex than those used in the proper construction of a brick, siding or traditional stucco exterior.
Ultimately, the water management/barrier choice comes down to expectations. We work in buildings and house our families in homes designed and built by people who comply with standard practices to ensure our safety and protect our investment. Improvements to construction methods are part of the continuing product development process. Shouldn’t water-managed EIFS be another advancement that fits logically into the equation for safe and reliable building practices?
Creating a more complex EIFS does not address the source of the problem.Used successfully in thousands of commercial and residential applications in the United States for 30 years, EIFS suddenly became the lightning rod for the moisture intrusion issue.
Are drainage systems the solution to moisture intrusion? Sto Corp., a manufacturer of cladding, coating and restoration systems, and producer of both barrier and drainage systems, believes that the best defense against moisture damage is to keep water outside the building. Before determining the merits of a barrier system over a drainage system, it’s first important to understand the nature of moisture intrusion.
The cause of moisture intrusion is water entering the structures around and through windows, doors, decks, chimneys and roofs, not through the EIFS itself. Furthermore, EIFS does permit evaporation through the wall surface to allow water vapor to escape and structures to dry, contrary to popular belief.
So, if EIFS works and water has been shown to enter through cracks and other openings, why use a drainage system that effectively turns a wall into a gutter?
The water runs through itWhen a window wall leaks, no one would dream of offering a product to drain the water down the wall. The logical choice is to deflect water at the point of entry and stop the leak at the source, not to re-direct leaks into the wall.
Keeping water outside the building starts with architectural designs that include sufficient eaves that shield walls from rain and flashing that channels and drains any penetrating water to the exterior. Proper caulking and attention to window and door installation is key, too, as is ensuring that decks are attached to the building correctly.
One has only to look at the thousands of trouble-free EIFS homes and commercial buildings to see that builders and contractors who employ sound construction practices and insist on using only compatible, code-compliant windows and other water-shedding components, do not experience problems with moisture intrusion.
Sadly, the pressure for new housing and inattention to the basics have been compounded by stretched local building department staffs and budgets that result in an overall deterioration in construction quality. This is borne out by moisture intrusion being reported now with vinyl, brick, wood and cladding systems requiring drainage. In addition, homes have become more complex structures with more complicated rooflines and more and larger windows that exacerbate any deficiencies in construction.
The rush to use drainage systems, unfortunately, does not address the root cause of moisture intrusion and is only a temporary fix. In fact, if drainage systems hide the symptoms of poor construction and non-compliance to codes, then the root cause may persist for a long time and, in effect, become institutionalized.
If the real cause of moisture intrusion is not corrected and a drainage system is used, buildings will still leak, but water will be directed out of sight through the walls. And with current drainage systems that rely on punching holes through building paper, there actually is a greater chance for water to penetrate through these perforations and cause the damage it was intended to prevent.
Clearly, the best solution is to keep water out. If a drainage system must be specified as some codes now insist, then the best approach is to use a hybrid drainage system that combines a barrier EIF system over a seamless moisture protection system. A premium product should be used with flashing at window penetrations and other rough openings to protect against water intrusion. Together with an EIFS adhesive, this hybrid system will provide for drainage at the source without the added installation expense of fasteners and the attendant chance for leaks that comes with punching holes in the wall.
What is yet to come?It is entirely conceivable that in a few years, a new round of moisture intrusion lawsuits may surface with conventional drainage systems. How could that happen? First of all, if the cause of the problem, water intrusion, isn’t addressed, then we’re only treating the symptom by using a drainage system as a solution. Secondly, because of the limitations of conventional drainage systems that perforate the building paper or housewrap, which offers only nominal moisture protection to begin with, it’s possible that moisture intrusion may still occur.
The industry needs to get serious about stopping moisture intrusion by keeping water outside of the building and not turn wall cavities into gutters.