Page 110 - Construction Waterproofing Handbook

BELOW-GRADE WATERPROOFING 2.73
Polyethylene sheets are available in both clear and black colors in thicknesses ranging
from 5 to 10 mil. PVC materials are available in thickness ranging from 10 to 60 mil.
Typical properties of vapor barriers are summarized in Table 2.9.
Vapor barriers are rolled or spread out over prepared and compacted soil, with joints
lapped 6 in. Vapor barriers can be carried under, up, and over foundations to tie horizontal
floor applications into vertical applications over walls. This is necessary to maintain the
integrity of a building envelope.
Mastics are typically available from manufacturers for adhering materials to vertical
substrates. In clay soil, where capillary action is excessive, laps should be sealed with a
mastic for additional protection. Proper foundation drainage systems should be installed,
as with all waterproofing systems.
Vapor barriers are installed directly over soil, which is not possible with most water-
proofing systems. Protection layers or boards are not used to protect the barrier during
reinforcement application or concrete placement.

SUMMARY

Systems available for below-grade waterproofing are numerous and present sufficient
choices for ensuring the integrity of below-grade envelopes. Project conditions to review
when choosing an appropriate below-grade waterproofing system include

● Soil conditions; rock or clay soils can harm waterproofing systems during backfill.
● Chemical contamination, especially salts, acids, and alkalines.
● Freeze–thaw cycling and envelope portions below frost line.
● Expected movement, including settlement and differential.
● Concrete cold joints to see if they are treatable for the system selected.
● Positive or negative system to see which is better for job site conditions.
● Large vertical applications, which are difficult with certain systems.
● Difficult termination and transition detailing, which prevents use of many systems.
● Length of exposure of installed system due to project conditions before backfilling.
● Safety concerns at project.
● Site/foundation access limitations.
● Dewatering requirements during construction.
● Concrete cure time available before backfill or other construction must commence.
● Adjacent envelope systems that the waterproofing system must be compatible with or
not damage.
● Scheduling requirements.
● Access for repairs after construction is complete.