CLEANING & MAINTENANCE
Designers must take cleaning and maintenance into consideration when designing masonry veneers. Water accumulation due to inadequate or uneven airspace in the cavity can cause an
undesirable pattern of discoloration which requires more regular cleaning. Movement that isn’t properly addressed can cause premature maintenance issues that require re-pointing grout joints or possibly replacing cracked bricks. Selecting the best possible stone or brick for the situation is the final design consideration to mitigate cleaning or maintenance issues in masonry Rainwater running over masonry can deposit excessive amounts of dirt on isolated areas of the wall leading to concentrated streaking and staining. It’s possible to choose a type and color of stone that doesn’t show streaking or staining; however, this issue can be addressed with a water repellent coating that must be reapplied every two to five years to remain effective.
PREVENTING DISCOLORATION
The construction of masonry walls can have structural and moisture related issues that prevent the façade from performing and lasting through a building’s life cycle. The building façade must resist discolorations to continue to provide the building’s aesthetic qualities as intended. It also must be capable of performing rain screen functions while resisting cracks or deteriorations that could lead to failures and endangering of the public.
EFFLORESCENCE CAUSED BY EVAPORATION
Efflorescence is a white deposit of salts left on the surface of masonry walls as the water evaporates. This phenomenon can occur when soluble salts are in contact with the masonry, either occurring naturally through the transfer of salts from the placed and/or mixed materials on the ground or if it’s in the mortar itself. While this is a complex subject, there are some simple measures to take during construction to prohibit efflorescence from appearing on masonry walls.
• Preventative Action – Always keep uncontaminated (and washed) sand off the ground and protected from contamination from rain, groundwater, or organic materials.
• Proper Drainage & Ventilation – “New building bloom” differs from long-term efflorescence in that after an initial period, the white chalky substance will disappear. This is likely due to water entering and remaining inside the wall. As discussed above, an air space greater than 1” will isolate the masonry veneer or stone and allow water to drain down off the back of the masonry rather than push out through the veneer – driving whatever salts collected with it. Proper ventilation in the cavity can lessen this salt drive, but contamination in the sand will typically keep showing up after cleaning as discoloration.
• Review & Modify Plans – By carefully reviewing details and taking into consideration the location of the building, you can prevent efflorescence from happening again. This may require a modification of plans to help keep water out of the cavity.
• Proper Climate Conditions – The best way to clean salt deposits is during warm, dry weather with a dry, stiff bristled brush, then washing it with low-pressure clean water and scrubbing it. A high-pressure wash should not be used as it will simply push the deposit back into the masonry.
If efflorescence returns, a clay poultice may be used on large, simple masonry details. This process includes wetting the wall for multiple days, then carefully creating a paste consisting of a clay mixture and distilled water to apply it. The clay paste is then secured with wire mesh for one month before removal to keep it in place and out of the sun and rain. Obviously, since this and other methods of drawing the salts out of the masonry are expensive and time-consuming, preventing the occurrence is a priority.
DISCOLORATION CAUSED BY INSUFFICIENT DRAINAGE
Poor drainage at the bottom of the masonry wall or at relief supports can also cause discoloration. Weeping the wall is vital to preventing discoloration and failure within the cavity caused by this. Weeps are required to be minimum 3/16” diameter and set at 33” O.C.
maximum spacing. Weep tubes or mesh vents along with mortar nets are recommended to keep openings from being blocked. Again, ventilation on the top of the wall can increase airflow and help moisture make its way out of the cavity properly.
IN SUMMARY
Throughout history, architects and builders have chosen masonry for its aesthetics, versatility, and durability. As the ultimate product for sustainable solutions, masonry is resistant to many environmental factors. It does, however, take a skilled craftsman to create a system that can resist ground movement, heat, and water while retaining its natural beauty.
At Zero/Six, we have honed our skills to build better wall systems, not only those that meet compliance regulations but exceed them. We hope that highlighting some of the above lessons will help you build a safer, cleaner masonry veneer.
