Page 231 - Masonry and Concrete

Footings, Foundation Walls, Basements, and Slabs
230 CHAPTER SIX

6.5.4 Waterproofing Membranes and Dampproof Coatings
The difference between waterproofing and dampproofing is one of
degree. Waterproofing is the treatment of a surface or structure to pre-
vent the passage of liquid water under hydrostatic pressure. Damp-
proofing is the treatment of a surface or structure to resist the passage
of water in the absence of hydrostatic pressure. Where waterproofing
is defined in absolute terms as preventing water infiltration even
under extreme conditions, dampproofing is defined in relative terms
as resisting—but not necessarily preventing—water infiltration under
moderate conditions.
Some building codes dictate the use of either dampproofing or
waterproofing on below-grade structures. Where no specific code
mandates exist, the decision to provide footing drains, a drainage type
backfill or drainage mat, dampproofing, or waterproofing should be
based on the amount of moisture in the soil and the level of the water
table. If the water table may fluctuate under different seasonal or
weather conditions, protection should include a waterproof mem-
brane in addition to subsurface drainage. If steel reinforcing is used in
concrete or masonry basement walls (including joint reinforcement in
concrete masonry), sufficient protection must be provided to prevent
moisture absorption into the wall and corrosion of the metal.
In dry and moderate climates with deep water tables, or on well-
drained sites with no history of groundwater problems and no possi-
bility of a rising water table, a dampproof coating will inhibit the
absorption of any groundwater which reaches the wall surface. Sub-
surface drainage can enhance the performance of the dampproofing by
minimizing the amount of water which reaches the wall. Dampproof
coatings provide resistance to moisture penetration by closing the cap-
illary pores in concrete and masonry substrates. Dampproofing will
not resist moisture penetration under hydrostatic pressure, and the
cementitious and mastic materials typically used for these coatings do
not have the ability to bridge across cracks. For dry or well-drained
soils with low water tables, Figure 6-38 illustrates appropriate
drainage and dampproofing measures.
1
3
Parging consists of a 8-in. to 2-in. thick coating of a portland
cement and sand mortar mix applied in two layers of approximately
equal thickness. The mix should be proportioned 1 part cement to 2-
1 2 parts sand by volume. The wall surface should be dampened before

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