Water Resistive & Air Barriers

WATER - RESISTIVE  BARRIERS

The proper design and installation of water resistant barriers is becoming increasingly important.  Water resistant barriers serve as a second line of defense against moisture (in its liquid state) entering the building.  The International Building Code, IBC, has specific language that requires the use of these barriers.  In section 1403.2 in the 2012 IBC code, it calls for a “weather-resistant” exterior envelope.  This envelope includes the installation of a “water-resistive barrier behind the exterior veneer”.  Integral with the barrier is the requirement for flashing to channel any water out of the envelope.  Using prescriptive language the IBC in Section 1404.2 defines the water-resistive barrier (WRB) as “one layer of No. 15 asphalt felt, complying with ASTM D 226 Type 1 felt or other approved materials  shall be attached to the studs or sheathing.”

The codes allow for alternate materials by showing equivalency in intended performance.  The International Code Congress, Evaluation Services (ICC-ES) established an “Acceptance Criteria” to prove required equivalency.  Because of alternate materials provision, and the Acceptance Criteria option, there are now several options that are available.  The alternates can be divided into three basic categories.  They are sheet materials, fluid-applied materials, and certain types of insulating sheathing. 

For sheet type materials, the specific Acceptance Criteria is entitled AC 38 Acceptance Criteria for Water-Resistive Barriers.  This would include some self-adhered types as well some polyolefin products.  Another form of a water-resistive barrier is a fluid applied coating.  The Acceptance Criteria that was drafted to show equivalency is AC212 Acceptance Criteria for Water-Resistive Coatings Used as Water-Resistive Barriers over Exterior Sheathing.    These materials are usually applied with trowel, brush, or spray applied.  When determining the appropriate water-resistive barrier for a project, it is important to make sure the material has the appropriate documentation for its intended application.

Note:  The limitations provided here are taken from appropriate building product manufacturer's source.  For more and the latest information relative to these limitations, it is recommended to contact either the representative association or a specific building product manufacturer.   A partial list of associations, and their links is provided on the home page of this site.

TYPES OF WATER BARRIERS

Asphalt Saturated Grade D Paper

Composition: Asphalt Saturated Kraft Grade D Breather Type Paper

Size: 40” x 240 sq. ft. or 340 sq. ft. rolls

Application: Applied over gypsum sheathing in 2 ply application.

Compliance:  ICC-ES AC 38 Acceptance Criteria for Water Resistive Barriers

Limitations:

Product should be covered as soon as possible.

Inspect installed product for holes or tears and repair as required.

The product is not recommended for horizontal, below grade, or roofing applications.

Installation:  Per Manufacturer’s Recommendations

Architectural Spec:  07 27 13 Bituminous Sheet Waterproofing

More and Latest Information Link:  Manufacturers website

 

Self-Adhered Water Resistive Membrane

Composition:  Rubberized asphalt compound integrally laminated to an engineered film.

Size:  48” x 100’ rolls

Application:  Applied over sheathing.

Compliance:  ICC-ES AC 38 Acceptance Criteria for Water Resistive Barriers

Limitations:

Product should be covered as soon as possible.

Inspect installed product for holes or tears and repair as required.

Use only when surface and ambient temperatures are and will remain above 40oF (4° C) during application and drying period.

Installation:  Per Manufacturer’s Recommendations

Architectural Spec:  07 25 Weather Resistive Barriers

More and Latest Information Link:  Manufacturers website

 

Polyolefin Water Barriers

Composition:  Spun-bonded polyolefin, non-woven, non-perforated water barrier

Size: rolls

Application:  Applied over sheathing.

Compliance:  ICC-ES AC 38 Acceptance Criteria for Water Resistive Barriers

Limitations:

Product should be used on vertical surfaces only.

The product is not recommended for horizontal, below grade applications.

Installation:  Per Manufacturer’s Recommendations

Architectural Spec:  07 25 00 Weather Barriers

More and Latest Information Link:  Manufacturers website

 

Fluid Applied

Composition:  Fluid-applied, acrylic-based primary air barrier material that cures to form a seamless membrane.

Size:  5 Gallon Pail

Application:  Applied over water sensitive substrates.

Compliance:  ICC-ES AC 212 Acceptance Criteria for Water-Resistive Coatings used as Water-Resistive Barriers on Exterior Sheathing, ASTM E 2357 Standard Test Method for Determining Air Leakage of Air Barrier Assemblies

Limitations:

Use only when surface and ambient temperatures are and will remain above 40oF (4° C) during application and drying period.

Do not use when temperature is above 100°F (38°C).

Material can be left exposed to weather for up to 6 months. Protect with cladding within 6 months of application.

Do not use on surfaces with standing water, below grade, or on surfaces subject to water immersion.

Not recommended to apply with roller or brush; use spray application.

Not recommended for spanning joints in sheathing greater than 1/8 inch (3 mm) wide.

Installation:  Per Manufacturer’s Recommendations

Architectural Spec:  07 27 26 Fluid Applied Membrane Air Barriers

More and Latest Information Linkwww.airbarrier.org

 

Foam Plastic Insulating Sheathing

Composition:  Expanded or extruded polystyrene or polyisocyanurate panels

Size:  Varies

Application:  Applied over exterior framing.

Compliance:  ICC-ES AC71 Acceptance Criteria Foam Plastic Sheathing Panels Used as Water-resistive Barriers

Limitations:

Sheathing panel joints must be taped and any penetrations sealed.

Insulating sheathing used must have been tested for water barrier applications.

Follow limitations of chosen insulating foam plastic sheathing.

Installation:  Per Manufacturer’s Recommendations

Architectural Spec:  07 25 00 Water-Resistive Barriers/Weather Barriers

More and Latest Information Linkwww.foamsheathing.org

 

AIR  BARRIERS

The 2012 International Energy Conservation Code (IECC) made it mandatory to include an “air barrier” in the exterior envelope.  Section C402.4.1 of the code is entitled “Air Barriers”.  It states that “a continuous air barrier shall be provided throughout the building thermal envelope”.   It does not prescribe on which side (interior or exterior) of the exterior wall that the barrier should be installed.  Any joints, seams, and penetrations must be properly sealed.

Two systems are seen as “deemed to comply” and do not require any further air barrier materials.  These two systems are:

  1. “Concrete masonry walls coated with one application either of block filler and two applications of a paint or sealer coating.”
  2. “A Portland cement/sand parge, stucco or plaster minimum 1/2 inch (12 mm) in thickness.”

As in the water barrier there is a prescriptive approach to air barriers.  The following list reveals 15 materials that are acceptable for use as an air barrier:

1. Plywood with a thickness of not less than 3/8 inch (10 mm).

2. Oriented strand board having a thickness of not less than 3/8 inch (10 mm).

3. Extruded polystyrene insulation board having a thickness of not less than 1/2 inch (12 mm).

4. Foil-back polyisocyanurate insulation board having a thickness of not less than 1/2 inch (12 mm).

5. Closed cell spray foam a minimum density of 1.5 pcf (2.4 kg/m3) having a thickness of not less than 11/2 inches (36 mm).

6. Open cell spray foam with a density between 0.4 and 1.5 pcf (0.6 and 2.4 kg/m3) and having a thickness of not less than 4.5 inches (113 mm).

7. Exterior or interior gypsum board having a thickness of not less than 1/2 inch (12 mm).

8. Cement board having a thickness of not less than 1/2 inch (12 mm).

9. Built up roofing membrane.

10. Modified bituminous roof membrane.

11. Fully adhered single-ply roof membrane.

12. A Portland cement/sand parge, or gypsum plaster having a thickness of not less than 5/8 inch (16 mm).

13. Cast-in-place and precast concrete.

14. Fully grouted concrete block masonry.

15. Sheet steel or aluminum.

For the gypsum panel application there is what is called the “Airtight Drywall Approach” (ADA).  This approach is the detailing that is required for using gypsum panels as an air barrier.  See the Technical Resource section of this website for more information.

The Air Barrier Association promotes the concept of an “Air Barrier System”. The system is a series of air movement resistant materials installed in such a way to provide a continuous barrier to air flow.  The air barrier system must be seamless across all six sides of the building.  The ABAA have a process to evaluate manufacturers’ various assemblies.  They also have a training program to certify installers.  For more information one should go to www.airbarrier.org.

Also, as in the case of water barriers, there are alternates that are available for consideration.  They fall into two categories, sheet and fluid applied membranes.

TYPES OF AIR BARRIERS

Self-Adhered Water Resistive Membrane

Composition:  Rubberized asphalt compound integrally laminated to an engineered film.

Size:  48” x 100’ rolls

Application:  Applied over sheathing

Compliance:  ASTM E 2357 Standard Test Method for Determining Air Leakage of Air Barrier Assemblies

Limitations:

Product should be covered within 30 days.

Inspect installed product for holes or tears and repair as required.

Use only when surface and ambient temperatures are and will remain above 40oF (4° C) during application and drying period.

Not to be used in direct contact with flexible PVC/vinyl membranes or gaskets.

Installation: Per Manufacturer’s Recommendations

Architectural Spec:  07 27 00 Air Barrier Systems

More and Latest Information Link:  Manufacturers website

 

Fluid Applied

Composition:  Fluid-applied, acrylic-based primary air barrier material that cures to form a seamless membrane.

Size:  5 Gallon Pail

Application:  Sprayed over water sensitive substrates in stucco applications

Compliance:  ICC-ES AC 212 Acceptance Criteria for Water-Resistive Coatings used as Water-Resistive Barriers on Exterior Sheathing, ASTM E 2357 Standard Test Method for Determining Air Leakage of Air Barrier Assemblies

Limitations:

Use only when surface and ambient temperatures are and will remain above 40oF (4° C) during application and drying period.

Do not use when temperature is above 100°F (38°C).

Material can be left exposed to weather for up to 6 months. Protect with cladding within 6 months of application.

Do not use on surfaces with standing water, below grade, or on surfaces subject to water immersion.

Not recommended to apply with roller or brush; use spray application.

Not recommended for spanning joints in sheathing greater than 1/8 inch (3 mm) wide.

Installation:  Per Manufacturer’s Recommendations

Architectural Spec:  07 27 26 Fluid Applied Membrane Air Barriers

More and Latest Information Linkwww.airbarrier.org

 

While reasonable effort has been made to ensure the accuracy of this information, we assume no liability for any errors or omissions on these pages.  Please verify all information with the organizations mentioned above.