Building Wall Assembly Types and the Role for Sealants and Adhesives

Posted on 2/20/2013 9:52:48 AM By Bob Braun

caulk, sealant, sealant application, caulk application 

In the blogs 1-18, I focused mostly on roofing applications.  In blog 19, I began looking at the use of sealants and adhesives used in building walls.  I plan to work the list of applications I previously presented and again which I have listed for your convenience below.  For each application, I will focus on the primary as well as the secondary functions e.g. air and water seals, energy savings, structural enhancements etc.  Along the way we will explore the current standards and codes related to each application.  Here is the list of just some of the more common building wall areas where a sealant or adhesive is frequently used:

  • Sealing the sole plate to foundation
  • Sealing the bottom of a stud wall to the floor
  • Sealing laps and seams in the wall sheathing
  • Attachment of wall sheathing
  • Attachment of the weather resistant barrier (WRB)
  • Sealing seam connections in the WRB
  • Sealing utility penetrations through the wall
  • Sealing utility penetrations within the wall cavity to adjacent areas
  • Sealing window/door to wall interface connections
  • Joining and sealing components of the window and door units themselves
  • Sealing the numerous types of joints in the façade
  • Attachments of decorative façade embellishments
  • Drywall attachment

First the Basic Exterior Wall Types: Exterior wall types can generally be classified as cavity wall, barrier wall, or mass wall.  Below I have a brief description of each.  The selection of the sealants and adhesives will depend on the materials used in the bulk wall assembly.  Certainly the installation details will vary as well.  For example, a pipe penetration in some cases will be sealed at the exterior façade and interior wall surface.  In others the seal should be done at three locations: exterior façade, drainage plane, and interior wall surface.  The final wall structure must manage water plus air and moisture ingress from both sides and must control vapor transmission in a way that also maximizes the wall’s durability and enhances energy efficiency.  Review the illustrations below from the Whole Building Design Guide.  As we look at the details for each application I will use examples of different wall types from time to time and these terms will appear again and again. 

Basics Elements of an Exterior Wall: 

  • Exterior Cladding
  • Drainage Plane
  • Air Barrier System
  • Vapor Retarders
  • Insulation
  • Structural Members

exterior wall

Note that there are only a few partial wall penetrations shown in each of these illustrations.  Real walls have many more penetrations than these idealized views. 
This is where sealants and adhesives become worth their weigh in gold.

Cavity Wall: This wall is also referred to as a screen or drained wall system.  This term is used to describe any brick, block, or concrete wall system installed over an air space used as a drainage plane to resist bulk water penetration.  The cavity is then vented to equalize the pressure to the exterior and reduce water being drawn in by induced negative pressure created by HVAC equipment and wind effects.  The drainage plane is then the primary air and water barrier.  Any wall penetrations should then be sealed to three surfaces e.g. surfaces 1, 2, and 3 in the above illustration, and surfaces 2 and 3 are the most important.  We will see how this is done effectively using a combination of products in future blogs for the different wall types.

A Cavity Wall Illustration

cavity wall

Barrier Wall: This wall relies on extremely weather tight outermost surfaces that will block water and moisture ingress.  Any failure in design or installation can result in wall damage from moisture ingress.

A Barrier Wall Illustration

barrier wall

Mass Wall: This wall depends on a combination of wall thickness, storage capacity to resist bulk water ingress.

Mass Wall Illustrations

mass wall

As shown above the mass wall may be subject to wetting at certain joints.  The mass wall depends on the alternate wetting and drying cycles for effective performance.  Thus, in some regions this has become a less popular design. 

Here is a link to the Whole Building Design Guide for those who wish to explore more details for building wall science.  

In Blog #22 and other future blogs we will review the existing and developing test protocols for various wall assembly types that contain penetrations of utilities, windows, etc.  Of course a question that is always asked after a successful test is “How will the wall assembly perform after aging” and protocols are developing for this as well.  Although this is a very tricky area to design a test protocol around, and also usually a very expensive one, accomplishments are now being achieved at a rapid pace, and code authorities are increasingly demanding this requirement as part of the approval process... 

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