Page 23 - Construction Waterproofing Handbook

WATERPROOFING PRINCIPLES—THE BUILDING ENVELOPE 1.5

FIGURE 1.3 Typical and common uses of “drip edges” to prevent tension
infiltration.

the concrete from drawing water from the soil through capillary action. Typical methods
to prevent capillary action in envelopes are shown in Fig. 1.5.
Hydrostatic pressure most commonly affects below-grade portions of the envelope that
are subject to groundwater. Hydrostatic pressure on an envelope is created by the weight
of water above that point (e.g., the height of water due to its weight creates pressure on
lower areas referred to as hydrostatic pressure). This pressure can be significant, particu-
larly in below-grade areas, where the water table is near the surface or rises near the sur-
face during heavy rainfalls. Water under this significant pressure will seek out any failures
in the envelope, especially the areas of weakness—the terminations and transitions