WestCon Tribune

May Review

Alternative Method of Wall Restoration Without Removal of Exterior Finish

Presented by Brett M. Ferrari, SE

Ferrari Moe, LLP, San Rafael, CA

A seven or eight year old, large single family, stucco home in Mill Valley had incurred severe wood decay in the framing members of the front garage wall. Some leaks were occurring on the deck and patio located above the garage unit that is attached to the house. The area had previously been worked on the year before, but after the rains came again, the water damage was still happening. It turned out that the deck was watertight but the parapet caps along the deck railing were the problem. Large nails holding the cap down allowed water to enter the interior of the wall. The amount of decay was so severe that the wall needed to be completely demolished and reconstructed.

The owner was adamant about not losing the six year growth on the front of the garage and hired Mr. Ferrari to figure out some way to replace the wall without removing the ivy. Although the client was aware that the wall could be replaced in kind and also that the cost could be significant for creating an alternative method, he was dedicated to finding a solution that saved the natural growth.

Except for the door frames, no organic materials remained in the wall at the end of the restoration. Since the entire wall needed to be removed with only the stucco remaining, it gave the opportunity to replace the wall with nothing of an organic nature. After kicking around numerous ideas, Mr. Ferrari attempted to take ideas that had been used for reinforcing large concrete walls and columns. With these concepts he came up with the idea of using an externally bonded fiber reinforced polymer (FRP) that can be adhered to the back side of the stucco.

The crew started by removing a small portion of the wall and testing the process. Since the wood elements of the wall were very decayed, it was easy to remove. The substrate was decent to work with and the staples were intact and were able to be utilized as a mechanical connection to hold the fiberglass scrim in place before the epoxy was applied. A representative from MasterBuilders came out to assist in the testing. After the primer was applied, a saturant went on with a roller. Then the patch needed to be pressed into the back of the stucco until a good bond was established.

When the test area proved the process would work, the remaining area of the backside of the wall was removed leaving only the stucco which was anywhere from an eighth to a quarter inch thick. This presented some tense moments as the wall was vulnerable and would actually move with the wind. One of the benefits of the product proved to be its flexibility which allowed the wall to move and not crack.

Next a hat channel was epoxied on with an FRP strip, and then a steel moment frame system was dropped in and attached with anchor clips. Galvanized steel studs were used to frame the remainder of the wall. A Durarock sheet was attached to the back of the wall and stucco was put on top so as not to include any plywood and a copper cap added for flashing with a pre-cast cap to be notched in later.

The process took about a month and a half and is not complete at this time due to waiting for the pre-cast cap to be made. The cost was about three times the that of simply removing and replacing the wall. But the bottom line is the client is very happy and has his original stucco walls with no cracks and all of his ivy untouched.

Ferrari-Moe, LLP, based in San Rafael, California is an Architecture/Engineering Services firm providing problem solving and design services throughout Northern California and Nevada. The company has developed an expertise in Architectural Diagnostics, especially as relating to waterproofing issues. They specialize in the investigation and evaluation of building failures especially as they relate to water intrusion through waterproofing membranes, curtain walls, window systems, roofs, wall claddings, and building joints. They conduct investigations into building failures and then develop remedial design solutions to correct the failures.

Our thanks to Mr. Ferrari for taking the time to share his knowledge and unique solution in an informative presentation.