A contractor from EcoSpect out of Syracuse, New York, was called out to look at a bowing concrete masonry unit (CMU) wall discovered in the basement during a home inspection being performed for a real estate transaction. EcoSpect determined that CFRP would be the best solution to strengthen the wall to prevent further inward movement while minimizing the cost, labor, and intrusiveness of the repair.

The Challenge
When a wall bows more than 2 inches, the repair becomes more cumbersome and costly. By using CFRP, EcoSpect provided the homeowners a more cost-effective solution than would be possible with traditional methods. Excavating and pushing the wall in would be more expensive, and there would be access restrictions to consider. If the homeowners approved the expense of pushing the wall back, CFRP would still be applied to strengthen the wall to prevent it from bowing again. Beams and tieback systems were also considered, since they provide resistance against deflection but they do not strengthen the entire height of the wall. Without adding strength from top to bottom with carbon fiber, future failures are still possible.

A carbon fiber pin connection to the foundation.

The Solution
EcoSpect chose the 400 GSM Bowed Wall Repair Kit (Unidirectional, Vertical) in 7-foot height due to its strength in one direction. Three additional walls would also be reinforced as a preventative measure. Proper surface preparation is one of the most important steps when installing CFRP. EcoSpect prepared the walls by grinding them to ensure the straps were engaged to their full capacity in order to resist any further inward movement of the wall, and to ensure a strong epoxy bond. Next, they repaired the damaged mortar joints. To ensure the repair was water-resistant, the cracked mortar needed to be knocked out and the joints were tuck-pointed. If the joints were not repaired properly, the walls were at risk of receding during the summer months when the moisture content of the soil is lower. Allowing any movement of the wall will further deteriorate the mortar joints which could create a wrinkle in the carbon fiber, decreasing the effectiveness of the repair. Nine repair kits were applied across the four surface-prepped walls for a total of 26 straps.

In addition, a single strap of 560 GSM, 12-inch wide CFRP (Bidirectional) was applied along the upper block course over the mortar joint that had started to open up where the movement manifested. The additional bidirectional strap provided strength in all directions. It was applied to increase the bond strength on the ends of the straps eliminating the possibility of a premature bond failure. The homeowners were thrilled they wouldn’t lose any square footage (due to CFRP’s thin profile) as is the case with traditional bowed wall repair methods such as steel beam reinforcement. The CFRP could easily be painted over, which meant there would be no visible trace of damage. EcoSpect was able to successfully reinforce the walls quickly and efficiently, resulting in a successful real estate transaction for the homeowners.