Direct Stucco & XL-Perm ULTRA VP Fluid Applied Air Barrier System Detailed Application Guidelines
For this week’s blog post, we tackle the application guidelines specifically associated with stucco base coats when applied directly over the fluid applied Pecora XL-Perm Vapor Permeable, Air, Vapor and Water Resistive Barrier System. Our Pecora Technical Service Team has evaluated the following field application methods which include two individual procedures for applying stucco directly over the vertical wall “field” and at the rough window openings that have been coated with the Pecora XL-Perm ULTRA VP fluid applied air barrier.
Direct Applied Stucco – WINDOW OPENING Application Procedure
Complete all joint and seam sealing with the Pecora XL- Flash liquid flashing and joint filler or other approved Pecora sealant. Allow the sealant to cure for a minimum one hour at 75°F/50%RH.
Apply the Pecora XL-Perm ULTRA VP fluid applied coating as the window flashing in a single 30 wet mil coat via an approved airless sprayer or ½” nap roller. Extend the liquid flashing a minimum 2” beyond the rough window opening on the exterior side of the wall surface.
A longer nap roller (5/8” or greater) may be required to achieve a 30 wet mil coat and will depend on the porosity of the masonry substrate.
Immediately broadcast a heavy and even coverage of 12/20 silica sand into the surface of the uncured XL-Perm ULTRA VP coating.
Allow the XL-Perm ULTRA VP coating to cure for a minimum 24 hours at 75°F/50%RH before applying the stucco base coat to the window opening areas.
Mix and apply the stucco base coat directly over the fully cured XL-Perm ULTRA VP (with sand). Follow the stucco manufacturer’s mix and installation guidelines.
Direct Applied Stucco – FIELD AREA Application Procedure
Complete all joint and seam sealing with the Pecora XL-Flash liquid flashing and joint filler or other approved Pecora sealant before applying the Pecora XL-Perm ULTRA VP fluid applied coating. Fill any “bug holes” or large voids present in the masonry wall surface with the Pecora XL-Flash.
Apply the XL-Perm ULTRA VP over the field wall area in a single coat at 10 – 14 wet mils via an approved airless sprayer or ½” nap roller. A coverage rate of 80 – 90 sq ft/gal can be expected over masonry wall surfaces.
Allow the XL-Perm ULTRA VP coating to cure for a minimum 24 hours at 75°F/50%RH before applying the Pecora P150 primer as the required stucco primer.
Apply the Pecora P-150 as a primer for the stucco base coat. Use a brush or ½” nap roller to apply the primer at a rate of 250 – 300 sq ft/gal. Reduce the coverage rate if the primer begins to run down the vertical wall surface.
The application of the P-150 primer is required based on laboratory pull off adhesion strength testing of stucco when direct applied to the Pecora air barrier coating. Not utilizing the P-150 as a stucco primer may result in inadequate adhesion of the stucco base coat and associated failures.
Allow the primer to dry a minimum one hour at 75°F/50%RH. Be aware that low ambient temperatures will extend the dry time of the primer. The primer should be firm but tacky and must not transfer to the finger when touched.
Mix and apply the stucco base coat directly over the fully cured XL-Perm ULTRA VP and P-150 primer. The stucco should be applied the same day as the primer otherwise re-priming will be necessary. Follow the stucco manufacturer’s mix and installation guidelines.
The data provided is informational only and does not constitute recommendations with regard to durability and/or warranty. It is the responsibility of the end user to ensure that performance data provided as well as field performance meets or exceeds requirements of local building codes.
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