Page 496 - Construction Waterproofing Handbook

13.12 CHAPTER THIRTEEN
If leakage starts at a lower elevation, the test should be halted until water penetration
stops, then restarted at higher elevations to verify that there are not several contributing
factors to the interior leakage. If leakage is not evident after testing all areas outlined in the
original test parameters, testing should move to adjacent envelope components. Water trav-
els a path of least resistance, and leakage might be entering the envelope through an area
far removed from where it appears on the interior. For instance, a leak occurring on what
appears to be a vertical wall might actually be caused by a leak in a balcony deck above
the wall area.
Horizontal envelope testing
On horizontal surfaces, such as plaza decks, it is often necessary to flood-test the deck to
determine the areas of leakage. To perform such testing, deck drains must be completely
plugged, including the secondary drainage level of two level drains. Then a specific area
must be closed off, usually be laying 2 4 lumber down that is sealed to the deck to pre-
vent water from traveling under the lumber. Water is then added to the area until it reaches
a certain height, usually 1 in. The water should be left standing until water infiltration is
documented or for at least 24 hours to verify that water is not traveling from this area to
other areas. The areas tested should not be so large as to prevent pinpointing the actual
areas causing the leakage.
Usually it is best to start testing of horizontal surfaces adjacent to any vertical envelope
area, which usually represents an area subject to the 90%/1% principle. The area sealed off
for this purpose should be relatively small, approximately 1 ft wide by a reasonable length
along the adjacent wall. Similar areas in the deck or plaza areas (planters, mechanical
penetrations) should then be tested. Then the main deck areas are tested, proceeding in a
checkerboard pattern, not testing an area adjacent to a tested area until it has had sufficient
time to be dried. Divertor boards should be left in place so that subsequent testing does not
allow water to enter an area that has already been tested.
The most difficult areas to test are those with loose-laid waterproofing or roofing sys-
tems, or divertor systems. Both of these envelope systems can permit water to travel and
infiltrate the interior spaces far from the actual point of breach in the envelope facade. In
addition, there might actually be several breaches in the envelope that all contribute to the
same interior leak, since water follows a path of least resistance that can be “fed” by water
infiltrating the envelope from several sources.
Below-grade envelope testing
Below-grade areas are among the most difficult to test accurately. Often the surrounding
landscaping must be completely removed for testing. In such situations, additional dam-
age is likely to occur to the below-grade envelope or waterproofing systems by the
removal of the backfill adjacent to the structure. Such damage prevents the accurate doc-
umentation of the original causes for leakage, eliminating any proper documentation for
legal situations. After such complete removal of backfill, the entire waterproof membrane
must be replaced due to the damage caused during excavation. This of course defeats the
purpose of testing.
Therefore, it is always best to attempt to pinpoint leakage without having to resort to the
destructive removal of any components or adjacent landscaping. Water applied at the surface
is likely to penetrate the soil irregularly, and there is no way to control the test parameters.