Page 302 - Forensic Structural Engineering Handbook

DEFECTS, DETERIORATION, AND DURABILITY 9.13

To both of these classifications, one could add another important criterion—whether defer-
ring repairs would result in greater cost later, not due to inflation, but rather due to an
increasing-rate mechanism. For example, postponing repair of freeze-thaw damage can
greatly expand the scope of future remedial work. Postponing remedy of the ponding con-
dition shown in Fig. 9.6 will lead to premature failure of the roof membrane, requiring
expensive roof replacement.

FIGURE 9.6 Severe ponding on a roof, which will inevitably lead to membrane failure if not
remedied.
Most building components require at least maintenance, if not replacement, during the
service life of a building under normal environmental loads. The “weakest link in the
chain” may compromise all others if not properly addressed. For example, neglecting to
replace deteriorated sealant joints may lead to the premature failure of adjacent components,
such as masonry freeze-thaw damage, wood rot, and structural steel corrosion.
Systems whose failure would pose a threat to public safety or building use require a longer
design life than those that pose little safety or economic threat. Table 9.3 lists the typical
design life of representative building components, compiled from several publications. 15,17,18

TABLE 9.3 Examples of Building Component Design Life 15,17
Building system Typical design life (in years)

Foundation >100
Structure >100
Exposed Parking Decks 30
Brick Units in Masonry >100
Mortar in Masonry 30
Wood Siding 20–40
Doors 25
Windows 20–40
Asphalt Shingles 15–30
Roof Membrane 10–30
Finishes 7–20
Floor Covering 5–10
Suspended Ceilings 10–20
Concealed Flashing 40