Page 230 - Construction Waterproofing Handbook
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RESIDENTIAL WATERPROOFING 4.5
he or she has completely overlooked the need for waterproofing below the slab and for
paying particular attention to the slab–wall joint.
The vast majority of leakage in basements is at this slab–wall joint or through cracking
in the slab itself. This is why so many remedial systems for residential basement applica-
tions are designed for installation over these poorly installed joints between the wall and
floor, with many incorporating a sump pump to alleviate the constant water intrusion
through the slab that was not treated during construction. You will find such experts as
Basement Technologies, Inc., which has a host of patented products designed for remedial
residential basement repairs, including its patented baseboard system for slab–wall joints.
There is available for residential construction prefabricated water stop/drainage-type
installations for use when the foundation and wall are placed first and the slab is poured
as in-fill. The system is attached to the perimeter wall at floor level to prevent leakage at
this transition between wall and floor.
Concrete block construction is rarely, if ever, acceptable for below-grade construction
for either residential or commercial applications. Waterproofing systems cannot ade-
quately cover the constant settlement and cracking that occurs during the life cycle of
block construction below grade, particularly at the mortar joints. However, block con-
struction does provide a satisfactory substrate for negative remedial cementitious water-
proofing systems, although usually these systems require numerous repeated applications
as the walls settle and move during the life cycle of the structure.
Prefabricated basements wall sections have become increasingly common for residen-
tial construction and are designed to provide a sufficient substrate for positive waterproof-
ing system applications (see Chap. 2). The panels, however, cannot accept a negative
waterproofing application because they usually are metal framed with only a closed-cell
insulation panel attached to the interior side. This means that should the primary positive-
side waterproofing fail, there is no means of applying remedial negative-side materials to
these systems, as there is with pored-in-place structures.
An additional problem with prefabricated residential basement wall systems is not the
walls themselves, but the basement slab and the detailing used to attach the walls to the base-
ment slabs. It is imperative that the manufacturer of such wall systems provide adequate
detailing to ensure a watertight transition from the wall to the floor slab. At the same time,
the contractor should take the necessary steps to install a slab waterproofing system that can
be transitioned to the wall panels. Again, since the panels cannot accept a negative applica-
tion, leakage at the slab–wall joint will be difficult to correct using remedial applications.
Some home designs do incorporate wood-framed basement wall construction. While such
construction may meet local building codes, which typically do not require waterproofing
methods to pass the code, wood frame presents too many challenges to provide an adequate
substrate for situations where water is encountered under hydrostatic pressure. Wood construc-
tion eliminates the possibility of using any cementitious remedial applications for repair, and
the only possible system for a remedial application is a positive system that is an adhered a
sheet membrane system (see Chap. 2). Such systems, however, have detailing at the slab–wall
transition that is beyond the capability of most residential contractors to install adequately, and
it would involve the use of a mud slab to install the membrane horizontally, as shown in
Fig. 4.1. This detail, with water stop and mud slab is probably beyond the capacity of most
homebuilders to install to ensure a watertight basement using wood frame construction.