Page 232 - Construction Waterproofing Handbook

RESIDENTIAL WATERPROOFING 4.7
relatively simple to install, meaning that even an inexperience home contractor can follow
the instructions and complete such an installation adequately.
If concrete block or wood framing is chosen for the basement construction, then such
prefabricated drainage systems are mandatory and should be installed on all vertical
below-grade wall sections as well to alleviate as much water pressure as possible to pre-
vent water infiltration into these poorer-performing substrates below grade.
Anytime a house includes a basement, it is imperative that above-grade water drainage
be installed properly to drain water away from the structure as quickly as possible. Of par-
ticular concern are roof drains and downspouts. The contractor never should be permitted
to position downspouts so that they drain directly adjacent to the structure. Downspouts
near any basement construction should be attached to a drainage pipe that traverses a dis-
tance of at least 10 ft from the exterior walls. This will prevent the water from percolating
down immediately adjacent to the basement wall and remove any unnecessary hydrostatic
pressure against the basement walls.

Positive versus negative waterproofing
Below-grade waterproofing systems include both positive (waterside) and negative (dry-
side) applications, as presented in Chap. 2. While both systems can be used in residential
construction, negative systems are probably the better choice under most common cir-
cumstances involved in residential construction.
Residential construction is often completed by relatively inexperienced contractors,
subcontractors, and construction workers who are unfamiliar with the requirements of the
90%/1% principle. These workers often are poorly trained and overlook the required
preparatory work and coordination among the various subcontractors. This leads to the use
of negative systems by default in most circumstances as the best choice for waterproofing
residential basements. Keep in mind, though, that prefabricated concrete panels and wood-
frame basement walls preclude the use of negative waterproofing systems.
Negative systems can be applied when a host of typically residential construction over-
sights have occurred during construction, including but not limited to
• Improper compaction of the soil prior to placement of the floor slab
• Disregard for any transition detailing between the floor–wall joint, including water stop
of cold joints
• Poor or no above- and below-grade drainage
• Concrete wall construction that is not properly vibrated or reinforced or of sufficient
high-strength concrete
The negative cementitious systems are relatively easy to install, and the only thing to
remember during construction is to place a cove at the wall–floor joint, which is then
packed with the negative waterproofing material to prevent leakage at this critical juncture.
However, even if the contractor fails to place this cove during construction, this can be
repaired by cutting out a joint after placement or installing a cant cove at this juncture,
depending on the requirements of the waterproofing system. However, residential contrac-
tors who use negative cementitious waterproofing systems should carefully instruct the