Water Penetration of Cladding Components—Results from Laboratory Tests on Simulated Sealed Vertical and Horizontal Joints of Wall Cladding

ABSTRACT: Considerable work has focused on the deterioration of jointing compounds used to seal building joints; less emphasis has been placed on understanding the consequences of seal failure, particularly in respect to watertightness. Jointing products are subjected to different climate effects; some induce aging in the sealant that in time leads to deficiencies. Deficien­cies may also come about from design faults or improper installation. Water entry at deficiencies may lead to a number of different deteriorating effects on the building fabric that may induce failure of other envelope components or premature failure of the joint sealant. Joints are also subjected to substan­tial wind driven rain loads, in particular atop multi-story buildings. The ap­proach taken in this study focuses on determining the fault tolerance of joint systems of a simulated wall panel when subjected to watertightness tests that emulate heightened wind-driven rain loads. Vertical and horizontal joints of 20 mm width and sealed with a one-component polyurethane product were subjected to water spray rates ranging between 1.6 and 6 L/(min-m2) and pressures of up to 2 kPa. Faults introduced to the sealed joint and representative of deficiencies through which water could penetrate consisted of cracks of 2 to 16 mm long introduced along the sealant to substrate inter­face. For specific crack lengths, the crack size related to the degree of joint extension, the extension reaching a maximum of 10 % of joint width. Rates of

water entry across the joint were determined for cracks of different lengths and size and the nature of water entry at deficient joints in which cracks were introduced was also examined. Results on vertical joints indicated that water readily enters open cracks in relation to the crack size, quantity of water present at the crack, and pressure across the opening. Water may also penetrate cracks of nonextended “closed” joints.

KEYWORDS: fault tolerance, joint deficiencies, sealant failure, watertightness, water penetration, testing

Introduction

Overview

Considerable work has focused on the deterioration of jointing compounds used to seal building joints, either to determine suitable methods to evaluate loss in their pertinent physical or chemical characteristics or establish test methods to evaluate their expected long-term performance. Less emphasis has been placed on understanding the consequences of seal failure along joints, in particular in respect to the expected loss in air and watertightness at the joint.

Jointing products are subjected to a number of climatic effects, some of which induce aging in the sealant that in time may lead to openings or defi­ciencies along the joint. Deficiencies may also come about from design faults or improper installation. Indeed, deficiencies due either to the effects of aging or from lack of attention to details or installation practice are inherent to any jointing system.

Joints are also subjected to substantial wind-driven rain loads atop multi­story buildings, in particular those located along an exposed coastline. Water entry at deficiencies along joints may lead to: leakage to the interior living space resulting in the formation of mold; moisture uptake by moisture sensitive components in the wall assembly, such as corrosion prone metal substrates or rot sensitive wood components; the premature loss in adhesion of the sealant. To what extent are joints, having small deficiencies through which water enters, vulnerable to water leakage when subjected to a substantial rain event, such as a typhoon, as might be experienced in Japan, or a severe thunderstorm or hurricane as in North America? Indeed, what wind-driven rain loads might be associated with a typhoon or hurricane and how often do these occur in a given climate? In other words, what risk might there be of water entry for any loca­tion, given a specific building height, facade type, and joint configuration and inherent deficiencies in the jointing system? How fault tolerant is the facade jointing system?

As an initial step, it is useful to briefly review the incidence and nature of failure at joints and thereafter, gain some insight into the nature of climate loads atop buildings subjected to wind-driven rain and loads associated with typhoon, hurricane, and storm events.

Water leak at crack of wall: 12% ^Water leak at the roof: 21 %

FIG. 1—Investigation of defects and complaints of building work in Japan [5].