Differential Creep, A Case Study

By: Dominic L. Pusateri

Clay bricks are as small as they are ever going to be the day they come out of the kiln.   Concrete is placed wet and air cured.  Over time, the concrete shrinks, while the bricks swell from exposure to water.  Cast-in-place concrete and wood framed construction clad in brick masonry cavity walls must allow for the different movement of these components.  

In the masonry cavity wall example shown, floor line relieving angles were not installed in sufficient frequency and the angles that were installed did not adequately allow for the differential movement.  The windows are attached to the CMU infill on the concrete superstructure and have a nosing that bridges onto the clad side of the wall.  The brick swelling/concrete shrinking dynamic has opened the sealant joints at the head and portions of the sill, while shearing the sealant at the jambs. 

Considering the age of the building, the average amount of annual movement per brick is about 0.0002".  The actual movement is on a curve, the additional differential will be less extreme than the initial swell/shrinkage scenario.

A more robust sealant profile and material can be used that will accommodate more movement than the original sealant.  Other concerns may be more pertinent, such as evaluating the degree of damage that has resulted to the window frames as a result of the movement.

The video shows a schematic of the movement and examples from the case study.  The case study illustrates the need for the building envelope inspector to give consideration to long term building movement in the analysis of the water management performance of installed systems. 
 

Diagnostic Water Testing

By: Dominic L. Pusateri   

In order to evaluate wall components, various tests can be utilized. Methods for the evaluation of these components are outlined in ASTM E 2128, Evaluating Water Leakage of Building Walls. One of the methods described in this standard involves directing water in a targeted fashion by building a dam around suspect areas and applying water. Hydrostatic head pressure comes into play only if the water is retained at some level in the dam. However, when water exits the dam as fast as it is poured into the dam, then hydrostatic pressure is not necessary for water to enter the components, mere capillary conduction is all that is necessary and the dam acts then more as a funnel, isolating water to specific areas. The benefit of the approach is that it is more precise as to the locations where the defect lies. This helps with the inference of the results when comparing the test locations to section details. 

Water By-Passing Window Perimeter Joints

By: Dominic L. Pusateri 

Perimeter caulk, also known as sealant, is used to transition windows to adjacent claddings; we call this a perimeter isolation joint.  The windows and claddings resist water and air infiltration with the help of the weather resistive barrier (WRB) at the cladding substrate.  The area between the cladding and WRB is known as the drainage plain.  In a recent blog post, I defined and quantified the volume of water that the drainage plain should be capable of managing.   Water at the drainage plain is commonly referred to as incidental water.   The incidental water should be controlled and directed to the exterior.  The interfacing of the weather resistive barrier at openings in the wall is critical but, because the weather barrier interfacing occurs behind the surface of the cladding and abutting components, it is often undervalued.  

Door Blower Usage

By: Abdullah Khaliqi

The door blower is one of many versatile tools utilized by R. J. Kenney Associates, Inc. (RJK ). This blog post highlights one of the many ways it can be used.

What is Incidental Water Anyway?

By: Dominic L. Pusateri

Incidental water is a term used in the building codes and referenced in specifications but what constitutes incidental water?