Page 497 - Construction Waterproofing Handbook

LEAK INVESTIGATION AND DETECTION 13.13
Further exacerbating the problem is the recognition that water will enter interior spaces
through the area of least resistance, this usually being the floor-wall juncture of below-grade
structures, far from where the waterproof membrane has been breached. Repairs made from
the negative side, interior, of the basement or below-grade areas, are only likely to cause the
leak to move to the next weakest point.
Leakage reporting can often provide answers to problems associated with below-grade
areas. If the leakage is documented as starting shortly after or immediately during rainfall,
leaks may be caused directly by the rainwater and surface runoff compounded by poor or
inadequate drainage. In this case the site conditions should be closely inspected during
rainfall for evidence of ponding water, slow drainage away from the building, or clogged
drains. Leakage in the envelope might be at higher elevations, possibly at the transition
between below-grade and above-grade envelope components.
If the leakage begins after rainfall, leakage is probably being created by a rise in the
groundwater level. In these situations, the leakage is likely to be at or near the lower por-
tions of vertical areas, most probably the wall-to-floor intersection. This leakage is often
evident by leakage through the interior near this juncture, often appearing behind interior
baseboards. It is unlikely that the leakage can be pinpointed without substantial damage
being done to the existing site conditions and positive-side waterproofing systems.
If sufficient information cannot be recognized from the leak reporting, construction
documents, and whatever visual inspection is possible to determine a reasonable cause for
the below-grade leakage, it is highly likely that a complete repair to the areas affected is
required. This would eliminate any specific repair to only the area causing the leakage, but
is likely to be as cost effective as destructive testing, which will likely require the complete
replacement of the waterproofing system in any event. If sump pumps are present (fre-
quently in residential construction) and no water is appearing in the sump, this is a likely
indication that the below-grade drainage systems are clogged and prevented from direct-
ing the water to the sump area for removal. It is recommended that an attempt be made to
clean these drains out first and monitor any improvement in the leakage after the sump
pump is functioning properly.
In these situations, if testing provisions cannot be created to pinpoint the leak cause,
rather than testing, it may be best to proceed to the investigation and remedial-action plan-
ning steps. Often in below-grade areas, this means recommending negative-side repairs or
additional drainage applications to move water away from the structure before it can travel
to the interior areas. These remedial systems are presented in Chap. 8.

Destructive testing
In certain situations however, destructive testing is the only applicable means to correctly
determine the cause of water infiltration and permit the proper repair method to be selected.
Destructive testing involves the removal of the outer layer of the envelope to expose interior
components for inspection and testing.
Destructive testing is typically only required when divertor systems are involved.
Divertor systems involve envelope components that permit water to enter that is later redi-
rected back to the exterior by a combination of dampproofing and flashings. Masonry
facades, EIFS water drainage systems, and curtain walls are examples of divertor systems.
It is often difficult to pinpoint the exact cause of failure in these systems without remov-
ing the primary barrier to expose the divertor systems.