Concrete and masonry : repairs and utilities. Page: 44
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b. WALLS ABOVE GRADE. Poor workmanship is
the chief cause of leaks in masonry walls above
grade. Unless masonry units are laid in full beds of
good mortar with all joints completely filled, walls
are likely to show leaks soon after the first rainy
season begins. Hairline cracks between mortar and
masonry are definite points of leakage.
(1) Transparent waterproofers. Using transpar-
ent waterproofing materials to repair leaks in walls
above grade is justified only when defects in con-
struction have been made good and when it is evi-
dent that moisture causing efflorescence is entering
the vertical wall face because of porous materials,
not defective joints. Select the type of transparent
waterproofer which experience shows to be most
effective under local climatic conditions. Do not
depend on results of laboratory experiments.
(a) Materials. Some transparent compounds for
waterproofing masonry walls which are usually sat-
1. Paraffin or very heavy mineral oils in
solution in light mineral spirits.
2. Metallic soaps of aluminum, zinc, and
so on, and salts of fatty acids.
3. Varnishes, usually mixtures of organic
oils and gums.
4. Sodium silicate, fluosilicates, and similar
materials in water solution.
(b) Preparation of surfaces. Fill all holes and
cracks in the wall face before applying waterproofer.
No "transparent surface-applied material can be de-
pended on to fill holes in masonry or correct struc-
(c) Application. The solutions are intended to
penetrate the masonry pores and are generally ap-
(2) Portland-cement paint. Portland-cement paint
hides the surfaces and waterproofs by filling surface
voids and crevices. It is intended for use on por-
ous surfaces of concrete, cement stucco, common
brick, concrete and cinder blocks, and similar mate-
rials. It bonds with porous surfaces and superim-
posed coats to form a highly durable cementlike
1. Portland-cement paint conforming to
Federal Specification TT-P-21, paint ;
cement-water, powder, is available in two
types and two classes of each type:
Type I, 65 percent portland cement.
Type II, 80 percent portland cement.
Class A, without siliceous aggregate, for
Class B, with siliceous aggregate, for open-
2. If color is required, color pigments
should be milled in by the manufacturer. Do
not add dry colors on the job because they
may streak when the paint is applied if
colors are not mixed in thoroughly.
(b) Preparation of surfaces.
1. Do not apply Portland-cement paints
until the masonry wall is at least 30 days old.
Allow poured concrete walls to dry for sever-
al months if possible beford*applying these
paints. Delaying the painting allows weather
to disperse the form oil, enables surface suc-
tion to become more nearly uniform, permits
removal of any efflorescence before painting,
covers checking which develops in masonry
surfaces, and causes less crazing of the paint
film. Removal of efflorescence is important
when dark paints are used because efflor-
escence shows more on dark than on light
2. Make sure surfaces to which portland-
cement paint is applied are clean and free of
loose dirt, scale, oil, form lacquer, or other
substances which prevent paint from striking
in and bonding to the wall.
3. Make surfaces rough or porous enough
to hold the paint. Concrete cast against ply-
wood or metal forms and some forms of ma-
sonry units are sometimes so smooth that
good paint adhesion cannot be obtained.
Roughen such smooth surfaces by light
sandblasting, dryrubbing with No. 16 car-
borundum blocks, or washing with 20 percent
builder's acid (muriatic). Rinse thoroughly
with water after the acid wash.
(c) Dampening the wall.
1. Before applying paint, wet the wall thor-
oughly with a garden hose giving a fine spray.
This water spray controls surface suction and
provides additional moisture which assists
proper hardening of the paint. Dampening
the wall by dashing water with a brush is
wholly inadequate. Apply the spray about
1 hour before painting. If the sprayed sur-
face dries rapidly, as it may in hot weather,
dampen it again just before painting.
2. Since dense concrete or masonry sur-
faces absorb moisture slowly, wet them in
two operations about 30 minutes apart.
Dampen large areas in advance of painting
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United States. War Department. Concrete and masonry : repairs and utilities., book, October 1946; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc29955/m1/50/: accessed May 18, 2021), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.