Stucco & masonry are some of the most prevalent cladding systems for multifamily and light commercial structures. Unfortunately, many projects do not incorporate a robust moisture protection system to protect these water-absorptive materials from mold & deterioration.
There is a growing market for "Moisture Remediation Specialists" that address moisture issues after they're identified. A full tear-off is often the only way to properly diagnose and fix the issue. These issues can be easily prevented in the design/build stage on the front end for a fraction of the cost of remediation.
The minimum building code for basic stucco application requires two layers of Grade D building paper or equivalent: one as the primary water-resistive barrier (WRB); and the second as a "sacrificial layer" between the primary WRB and the metal lath and scratch coat.
For the primary WRB, we recommend using a WRB that has a tri-laminate substrate that can resist surfactants and provides superior water holdout.
We also recommend building with at least a ¼ in. air space to allow ventilated drying behind the stucco or stone. This air space provides pressure moderation so that air can move behind the stucco or stone to dry on the backside. The drying capacity of a ¼ in. air space can drastically reduce the moisture retention in the wall to avoid staining, cracking, deterioration, or mold growth on the sheathing. Use a rolled rainscreen product like Slicker Max that incorporates a ¼ in. air space matrix adhered to a fabric that serves as the secondary sacrificial layer.
When using a pre-weatherized sheathing, like Huber's Zip System®, the building envelope solution is exactly the same as it is for OSB sheathing.
It is important to note that the incorporated WRB on the Zip System panels does not meet the requirement of water resistance equal to or greater than 60-minute Grade D paper, and therefore cannot be used as the primary layer per Exception to R703.7.3. Stucco or Stone applied over preweatherized sheathing still needs two additional WRB layers.
Rigid foam is a flat-to-wall low perm board that can contribute to moisture damage in a water entry event if there is no pathway for water to escape. HydroGap provides a means to drain water underneath the foam without reducing the thermal resistance of the wall.
In a Non-EIFS application, apply drainable housewrap over sheathing and continue with insulation, rainscreen with sacrificial layer, lath, scratch coat, then stucco or stone.
In an EIFS (synthetic stucco) application, apply drainable housewrap directly over sheathing and continue with insulation and EIFS layers.
HydroGap Drainable Housewrap protects the elegant finish of fiber cement siding by creating a gap via 1mm spacers which promote drainage behind the cladding. These unique spacers remove 100 times more bulk water from walls than standard housewraps. Trapped moisture will cause damage to your wall system and creates an environment for mold and rot.
Strength & durability matter when it comes to protecting your sheathing. Stucco & masonry products have chemicals in them that can cause inferior WRB's and building paper to deteriorate overtime. FlatWrap HP is a tri-laminate wrap that protects the important water holdout film by sandwiching it between 2 layers of a premium non-woven wrap. Its durability can withstand the rugged installation that's typical of stucco applications.
Given the absorptive tendencies of stucco & masonry, you need to make sure that any water that gets in, has a chance to escape and dry. Slicker Max creates a 1/4 in. - 7/16 in. space that promotes drainage while allowing air to move, drying your wall from the inside out. The added fabric acts as a bond break that prevents mortar from entering the wall cavity during installation.
Use HydroFlash for all of your window and door flashings needs. HydroFlash is an aggressive peel-and-stick self adhered flashing that out-performs other butyl and rubberized asphalt versions. The specially formulated bloc co-polymer can be applied to damp surfaces and installed down to 0° F.
HydroCorner Sill Treatment is an affordable option for protecting a window sill from moisture intrusion. Place one HydroCorner in each of the bottom sill corners, and then cover with a piece of HydroFlash for a quick and easy-to-install sill treatment.
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