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Hayder Seeks: Sealant Slip-ups

08.28.18   Hayder H. Al-Hilal, PE, SMSI, CIP-1, CCI-2, Level 1 Thermographer, ICRI CSMT | More by this Author

Hayder Seeks: Sealant Slip-ups

FAQ: Hayder, I’m having problems with my masonry walls. Water is leaking into the interior along the drip edge at windows and doors. I have sealed all drip edges, but it seems that water is still getting in through the sealant. Water leakage is more serious now and my masonry walls are bulging and cracking above sealed windows and doors. How SME can help?

Answer: During assessment of many building enclosure elements, we run into conditions where sealant is misused to seal outside edge of masonry-to-steel lintel transition (drip edge) above wall openings, as shown below.
Sealant misused to seal outside edge of masonry-to-steel lintel transition (red arrows).

In general, masonry walls are considered porous. Porosity coupled with deteriorated mortar joints and other defects can create conditions for moisture infiltration, especially during heavy wind-driven rain events. The misuse of sealant to seal the outside edge of the drip edge will result in water accumulation in the space between the steel lintel and masonry, creating favorable conditions for steel corrosion.

Significant corrosion will result in pack-rust development. Pack rust is a condition where corroded steel occupies a larger volume than the original steel material. This causes expansion at surfaces of embedded steel materials and high tensile stresses in supported wall elements that can easily crack/delaminate the surrounding masonry, leading to bulged and cracked masonry above the opening and more serious water leakage issues. Additionally, this condition may lead to compromising the structural integrity of the steel lintel as a result of the original steel section loss.

The illustrations below demonstrates how the misuse of sealant coupled with missing flashing and weep holes has resulted in significant corrosion and pack-rust development at the CMU-to-steel lintel transition.


The porosity of exterior CMU walls, missing flashing and weep hole system, as well as the presence of sealed outside edge, prevent water entering the wall system from drying or exiting to the exterior of the enclosure.


Absence of flashing and weep system has resulted in water accumulation in the space between the steel lintel and CMUs, leading to corrosion and pack-rust formation. Pack-rust formation resulted in wall bulging and displacement of CMUs and window panels. Black arrows indicate direction of forces generated by pack-rust formation on surrounding materials.

The resulting damage to a building enclosure system looks something like this:

Severely corroded steel lintel with significant pack-rust formation on the built-up steel lintel. Note the sealant that had been applied at the CMU-to-steel lintel transition (drip edge).

Selective removal of masonry above openings and installation of a through-wall flashing system (consisting of impervious membrane and weep holes) to collect and divert rainwater entering the building enclosure is required to solve the problem.

Is your building exhibiting water leakages at openings? Are your masonry walls bulging or cracking? SME can help!

From assessing the condition of building materials, structures and equipment, to identifying causes of failures and developing maintenance, rehabilitation and restoration solutions, SME’s Building Materials team offers comprehensive services to optimize the service life and performance of your facilities, structures and equipment. For more information contact Hayder Al-Hilal.

 




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