Preventing Efflorescence
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Simple Tips for Preventing Efflorescence
 Efflorescence
is a crystalline deposit, usually white, that may develop on the
surfaces of masonry construction. Often it appears just after the
structure is completed—when builder, architect, and owner
are most concerned with the appearance of the new structure. Although
most efflorescence is harmless and temporary, recurrent efflorescence
indicates a chronic moisture problem. Efforts should be taken to
correct the moisture problem, thereby preventing and eliminating
recurrent efflorescence.
A combination of three common circumstances is necessary for efflorescence
to develop: (1) soluble compounds in the masonry, (2) moisture (for
transport), and (3) evaporation from the surface. If any one of
these conditions is eliminated, efflorescence will not occur. Given
the characteristics of masonry materials and construction, it is
virtually impossible to eliminate all the soluble salts, construct
walls containing no free moisture, or completely eliminate paths
of moisture migration. However, steps can be taken to minimize the
extent of these three contributing factors. Good workmanship is
one of the most effective means of limiting the potential for efflorescence.
Following are some simple preventative measures.
Provide for good drainage
1. Correctly install waterstops, flashing, weepholes,
and copings per design details. Maintain clean cavities and unobstructed
weepholes during the construction of cavity walls.
Construct good mortar joints
 2.
Tool all mortar joints with a V- or concave-shaped jointer to compact
the mortar at the exposed surface and create a tight bond between
mortar and masonry unit. Weeping, raked, and untooled struck joints
are not recommended in exposed applications.
3. Assure that joints are properly filled. Deteriorated
or defective mortar joints should be repointed to keep moisture
out of the wall.
Ensure proper curing
4. Assure adequate hydration of cementitious materials
by protecting masonry from cold temperatures, premature drying,
or improper use of admixtures.
Limit water entry
5. Apply paint or other proven protective treatment
to the outside surfaces of porous masonry units. Caulk around window
and door openings. Seal or otherwise repair cracked joints in walls.
Also, use through-wall flashing at ground level to prevent capillary
rise of ground moisture.
6. Install vapor barriers in exterior walls (interior
surfaces of exterior walls) or apply vaporproof paint to interior
surfaces and use designs that minimize condensation within masonry.
7. Carefully plan the installation of lawn sprinklers
or any other water source so that walls are not subjected to unnecessary
wetting.
8. If feasible, use wide overhanging roofs to protect
walls from rainfall.
Limit moisture driving forces
9. Provide for pressure equalization between the
outside and the void within the masonry wall by appropriate venting
of cavities.
Other Resources
Find out more about what causes white deposits on the surface of
masonry, how to prevent them, and methods for removal. Check out
PCA's Trowel Tips:
Efflorescence (IS239)
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