Moisture Protection: Which Products Make the Cut?

Words: Dan KamysMay 2016 [caption id="attachment_12762" align="alignnone" width="600"]masonry Moisture Protection Figure 1.[/caption]

By Keith Lolley

Athletes learn early on the value of teamwork. If everyone works together, the success rate is far greater than going it alone. Being from New England and a huge New England Patriots fan, I have enjoyed watching Bill Belichick, the head coach of the New England Patriots, become extremely successful on the football field. He can interchange any player, no matter who they are, and get them to work in unison with the others and perform at a high level. Although this recipe has earned Belichick four Super Bowl victories with the Patriots, this tactic rarely works in designing a winning wall system. When building the best wall system to defend against moisture intrusion, it is important to know and understand your competition…Mother Nature. When we think of moisture, rain, snow and wind are most likely the first examples that come to mind. However, climate zone effects, solar-driven moisture and capillary action need to be understood as well. Even man-made mistakes need to be factored in. [caption id="attachment_12761" align="alignright" width="275"]masonry Moisture Protection Figure 2.[/caption] Let’s start with climate zones. Walls built in geographic areas receiving more than 20 inches of rainfall a year need to be designed to address excessive moisture intrusion. Since a majority of claddings used in masonry applications (brick, manufactured stone, stucco, EIFS, fiber cement, and natural stone) are absorptive claddings, it needs to be understood that moisture will pass through the veneer and into the wall. So what are the three most common defense formations? They are direct, vented and ventilated (Fig. 1).

Moisture Defense Systems

The direct wall system is commonly found in residential construction. This method installs the cladding directly against the sheathing, or backer wall. This formation gives little hope to successfully handling moisture intrusion (Fig. 2). When moisture gets past the veneer, it has nowhere to go, thus remaining trapped. Over time, this trapped moisture will take the path of least resistance and find its way into the inner wall via cracks caused by differential movement, incorrect installation practices, and simple product failures. These issues will lead to mold, rot, and corrosion of building materials, poor indoor air quality, and eventually structural damage (Fig. 3). The monetary value of the damage can easily extend into the six-figure range, and most insurance policies offer very little liability coverage when it comes to rot and moisture-related issues. [caption id="attachment_12760" align="alignnone" width="600"]masonry Moisture Protection Figure 3.[/caption] Masonry veneers are porous and have the ability to crack over time. The smallest fissure can allow large amounts of moisture into a wall system through capillary action. Capillary action draws moisture into a wall system due to pressure differentials between the outside and inside wall system. Think of when you were younger and went to the doctor for a blood draw. They would put a glass tube over the puncture area of your finger. The blood from your finger would rise up into the small tube. That is capillary action at work. One way to reduce the harmful effects of capillary action is by neutralizing the air pressure between the inside and outside wall. Creating a capillary break across the entire surface area of the wall from the bottom all the way to the top of the wall will help moderate these pressure differentials. This is known as a ventilated or rain screen wall system. These wall systems are extremely effective when it comes to allowing moisture to drain, not remain (Fig. 4). [caption id="attachment_12759" align="alignnone" width="600"]moisture, protection, products Figure 4.[/caption] Unlike a vented cavity wall system, a ventilated rain screen wall system creates air pressure moderation between the inside and outside environment by establishing a capillary break and placing vents at the bottom and top of the wall. This allows air to be introduced into the cavity and circulate in a convective fashion. This drying effect is as important as the drainage ability created by this air space (Fig. 5). [caption id="attachment_12758" align="alignnone" width="600"]moisture, protection, products Figure 5.[/caption] In the past and sometimes still today, furring strips are used to create a capillary break between the veneer and inner wall system. Furring strips are pieces of wood cut and installed in a vertical application. Since furring strips are typically made of wood, they can retain water. Most furring strips do not allow for cross-ventilation, and they can have a wall-to-siding coverage area of up to 15%. This means 15% of the wall has the ability to trap moisture. These products are also more labor intensive compared to newer, alternative methods gaining in popularity. Engineered polymeric rain screen drainage mats, also referred to as rolled rain screen drainage and ventilation mats, are manufactured from polypropylene or nylon. Many of these materials are in the form of an entangled matrix. Some come with a heat-bonded facing filter fabric, while others offer a multi-step process. Engineered rain screen drainage mats with a heat-bonded filter fabric, such as Mortairvent® by Advanced Building Products, are highly recommended for masonry applications. These rolled rain screens are installed with the filter fabric facing out. This fabric keeps the air space clear of mortar debris, allowing moisture to pass through and drain down and out of the wall (Fig. 6a and b). The filter fabric also acts as a bug screen, which is very important in certain geographic areas. [caption id="attachment_12757" align="alignnone" width="600"]moisture, protection, products Figure 6a.[/caption] [caption id="attachment_12756" align="alignright" width="300"]moisture, protection, products Figure 6b.[/caption] Entangled matrix rain screen products without a filter fabric have the ability to be stretched during installation, which can cause a wavy appearance over the surface area of the wall. Installing a rolled rain screen with a filter fabric eliminates the stretching. In most cases, engineered rain screen products are anywhere from about 1/4 inch (6 mm) to 1 inch in thickness. Keep in mind that the whole purpose of these products is to help create a clear air space across the entire surface area of the wall. The smaller the air space, the less air needed within the space for neutralization to occur. The larger the air space, the longer it takes to achieve pressure neutralization. Since moisture travels through the air, essentially a wider air space will introduce more moisture into the wall system while achieving pressure neutralization. [caption id="attachment_12755" align="alignright" width="300"]moisture, protection, products Figure 7.[/caption] When specifying an all-wall rain screen, be sure to factor in plus-or-minus a finger width. As you can see in Fig. 7, the drainage mat should be slightly less than the size of the intended air space. Since most air spaces are a nominal distance, a 1-inch drainage mat might not fit the specified 1-inch air space. Plus, it is important to give the builder room for his/her fingers to install the product. The following are some of the advantages to specifying and installing an all-wall polymeric rain screen (Fig. 8):
  • Most products are mold and mildew resistant.
  • Most have multi-directional drainage and ventilation.
  • Most will not crack to the point of failure.
  • Most are resistant to known chemicals typically used on jobsites.
  • They are cost effective.
  • Most qualify for LEED credits.
  • Most have a Class A fire rating (ASTM E84).
  • Most have a heat-bonded filter fabric.
  • Engineered rain screen drainage mats with a heat-bonded filter fabric are a one-SKU product. One rain screen for all wall applications keeps inventory levels down.
[caption id="attachment_12754" align="alignnone" width="600"]moisture, protection, products Figure 8.[/caption] When specifying and building with an engineered rain screen drainage and ventilation mat, be sure the product has been tested to the standards found in ASTM 2925-14 — not just the drainage portion of ASTM 2925-14, but all the criteria of that standard. These tests consist of Heat Aging (ASTM D3045), UV Testing (ASTM G154), Drainage Efficiency (ASTM E2273), Surface Burning (ASTM E84), Compression Testing (ASTM D6108), Immersion Testing (ASTM D5322), and Nominal Thickness Test (ASTM D5199).

Throughwall Flashing

The next product within the wall to review is the throughwall flashing. Throughwall flashings, sometimes known as the “I forgot it” item, play a crucial role in moisture protection within a wall system. With so many options, it can become confusing to specification writers and installers, too. The first question an architect or designer needs to ask is, what is the intended life of the building? Is this a hospital expected to last 80 years, or is this going to be a strip mall that will be bulldozed in six years to make room for the next big thing? For argument’s sake, let’s say the building is a college dormitory with a 60-year life expectancy. What throughwall flashings are available on the market? There are self-adhered rubberized asphalt flashings, PVC flashings, composite metal flashings, and heavy pre-formed metal flashings. Which flashings will last the expected 60 years? PVC flashings are not a good choice here. Most are not recommended for throughwall flashing applications due to plasticizer migration, which causes the membrane to become brittle. Some manufacturers will give this membrane five to seven years. As you can imagine, cracked and brittle membranes tend to not make for a good flashing. Replacing failed flashings can cost up to $3 per foot (see Fig. 9). [caption id="attachment_12753" align="alignnone" width="600"]moisture, protection, products Figure 9.[/caption] Self-adhered rubberized membrane flashings have great self-sealing characteristics and are economically priced; however, make sure the manufacturer of these flashings will guarantee the flashing to last the expected life of the wall. Do any self-adhered rubberized asphalt flashings come with a 60-year warranty? Can you find self-adhered rubberized asphalt flashings that are UV resistant? Can you find one that guarantees 100% adhesion for the expected life of the wall? If the answer is no to any of these questions, you need to reconsider which flashing is right for the job. Self-adhering rubberized asphalt flashings need to factor in a metal drip edge and a termination bar. These additional items must be considered when pricing for the most economical flashing. Keep in mind that most drip edge material is stainless steel. When bonding a rubberized asphalt product to a stainless steel drip edge exposed to the direct sunlight, the metal drip edge will heat up, causing the rubberized asphalt to potentially “drool.”

Composite Metal Flashings

Let’s move on to the next category of flashings: composite metal flashings. Copper and stainless steel flashings will last the life of just about any wall system. Copper-laminated flashings have a successful track record dating back more than 100 years. These typically come in three-, five- or seven-ounce thicknesses. These copper products are compatible with acids and alkali in fresh mortar. They are UV resistant and pliable, which makes them easy to work with. They also come in roll form, so there is no soldering, and reduced lap joints help achieve a watertight seal. [caption id="attachment_12770" align="alignright" width="300"]moisture, protection, products Figure 10.[/caption] Not all composite copper or stainless steel flashings are created equal, however. If the wall system calls for the use of an air barrier, make sure the copper or stainless steel flashings are compatible. Advanced Building Products has a non-asphaltic version of copper-laminated flashing compatible with most known air barriers on the market called Copper Sealtite® 2000 (Fig. 10). Some asphalt-coated copper flashings are not compatible with various air barriers. There is always a composite copper or stainless steel flashing right for the job; just make sure you choose wisely. Remember, don’t install or specify a five-year flashing in an 80-year building.

Proper Installation of Throughwall Flashings

When installing throughwall flashings, there are only three recommended ways to do so (see Fig. 11). With block backup wall construction, the flashing is often placed in the bed joint of the block. One issue here is that the flashing remains exposed for a prolonged period of time, running the risk of being damaged before the veneer is installed. The use of a reglet is common in poured concrete backup walls; however, the most popular form of flashing installation is the use of a termination bar. By using a termination bar, the contractor can start by installing the flashing flush with the outside face of the brick and then bring it back into the wall and secure it up the wall accordingly. This allows the mason to be sure the flashing has successfully been installed “through the wall” (Fig. 12). The flashing is also now installed when the contractor is ready for it, not so far ahead that it is susceptible to weather. It is important to avoid installations such as that shown in Fig. 13. [caption id="attachment_12769" align="alignnone" width="600"]moisture, protection, products Figure 11.[/caption] [caption id="attachment_12768" align="alignnone" width="600"]moisture, protection, products Figure 12.[/caption] [caption id="attachment_12767" align="alignnone" width="600"]moisture, protection, products Figure 13.[/caption] Throughwall flashing failures usually take place at two locations: the corners and the extension of the throughwall flashing itself. It is highly recommended that pre-formed metal flashing corners be used on all masonry applications. They are installed quickly and are reliable. Oftentimes multiple flashing pieces are cut and spliced at corner locations and sealed with mastic. It is difficult to achieve a watertight seal using this technique. Moisture usually finds its way into the wall system at the base of the corner location. Mortar deflection devices are often used in cavity wall applications. These products range in thickness between 1/4 inch and 2 inches. The goal of these products is to suspend excess mortar droppings away from the weep vents. The mortar deflection is to be placed directly on top of throughwall flashings. Most mortar deflections are made from either nylon or polypropylene in an entangled matrix formation. These products come in configurations such as dovetail, maze design, or straight strip. As a manufacturer of these three configurations, I can tell you they all work well. The key is rigidity. Make sure the mortar deflection you specify is rigid enough to hold the weight of excess mortar droppings. Advanced Building Products makes a configuration called Mortar Maze, which provides interlocking mortar deflection. Remember, if the flashing must be continuous, so should the mortar deflection (Fig. 14). [caption id="attachment_12766" align="alignnone" width="600"]moisture, protection, products Figure 14.[/caption] When using a mortar deflection, it is important that the throughwall flashing extend a minimum of 4–6 inches above the mortar deflection. This will prevent moisture from entering the wall system at locations above the mortar deflection. It is also important to make sure drainage devices are placed in the head joints. Cell vents, or weep vents, consist of a plastic honeycomb design. These products are placed in the head joints of a brick wall spacing every 24 inches. Plastic weep tubes are often used. Placement for these products is recommended every 16 inches. Another option is to simply leave the head joint open every 24 inches. [caption id="attachment_12765" align="alignnone" width="600"]moisture, protection, products Figure 15.[/caption]

Conclusion

As you can see, building a wall system to fight moisture intrusion is much like building a team. There is no one product that will save the day. Numerous products need to be put in the wall together and tested to make sure they will perform as intended (see Fig. 15). As a manufacturer of moisture protection products, it amazes me to see time and time again products with a limited life expectancy put in a wall and expected to perform at the highest level for an extended period of time. Think back to the beginning analogy. Bill Belichick is the exception, not the rule.

Keith Lolley is a graduate of Southern New Hampshire University with a bachelor’s degree in business management. He has been involved in the construction industry for 18 years and is the vice president of Advanced Building Products while currently holding a seat on the board of directors for the Building Enclosure Moisture Management Institute (BEMMI). Lolley can be reached at klolley@abp-1.com.

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