General

In this chapter, some fundamental concepts of durability related to the design of residential buildings are addressed. This background information is intended to establish a baseline of understanding and to introduce concepts important to developing a realistic perspective on durability. It is important to appreciate the significance of durability when attempting to balance or optimize many factors that define the realities of construction and the service life of a building.

Before discussing the concept of durability, some unrealistic notions surrounding the topic should be dispelled:

• Durability does not mean perfection, but it does require diligent effort for continual improvement.
• Durability does not mean that things should last forever, but it does require that reasonable life expectancies are achieved or exceeded.
• Durability doesn’t mean that all problems are foreseeable for designers; there are many examples of problems beyond the prediction of designers, such as polybutylene plumbing and initial EIFS systems.
• Durability doesn’t mean fail-safe installation, but it does demand a level of care that matches skill levels and quality of workmanship with the nature of the work being performed and consequences of installation defects.

Simply put, durability is a multifaceted challenge. It involves nearly all aspects of construction, including planning, design, material specification, construction management, work force skill, and quality control. This particular document addresses the residential building design and specification phases of the construction cycle, although several topics naturally stray into work site issues and quality control.

To fail to plan for durability is a plan to fail. For example, durability problems are frequently associated with avoidable construction defects. A 2007 ASHRAE study found that out of 17,000 construction defect claims, 69% were the result of moisture-related defects in construction of the building envelope.1 In recent years there have been settlements costing U.S. homebuilders tens of millions of dollars to repair and correct water damage caused by construction defects. Furthermore, the USDA Forest Product Laboratory reports that “termites invade more than 600,000 homes and cause over $1.5 billion in damage annually.”2 We could go on with more statistics and figures, but clearly there is plenty of evidence that the factors influencing durability really do matter, and that there is plenty of room for improvement.

While builders and designers cannot foresee all durability issues, where they can affect better durability is in informed selection, integration, and application of components, materials, and building systems. This process is far from simple as an ever-changing menu of products and systems is used to optimize cost, performance, aesthetics and consumer appeal, code compliance, and constructability. Further, a change to any one of these factors (e.g., a major uptick in material prices or a code change) can trigger a change from “Assembly A” to “Assembly B.” If Assembly B wasn’t vetted for how the new product would affect the home’s durability, the builder has just incurred additional risk. These material changes also cannot be disassociated from changes that occur in the labor force. New materials or methods introduced into a construction process require a means of not only understanding the system or product, but also training of affected trades and quality control. Further downstream with the homeowner, these changes may also place new demands or expectations on home maintenance.

How can a builder take action today and better prepare for the durability challenges of tomorrow? This chapter and the remainder of this course offer answers to this question. Section 2.2 defines durability and provides resources to engage both the builder and consumer in the pursuit of durability. Section 2.3 provides a brief overview of common durability problems in the present or recent past—which serve as lessons to apply better strategies in building the homes of tomorrow.