South Wall Discovery Project: Initial Report

ON THREE OCCASIONS during the past two decades, structural engineers have recommended that we do test cuts into the south wall of our sanctuary. The goal: to enable more reliable cost estimates for waterproofing and possible structural repair work, hopefully later this year. Given more than two decades of known water intrusion and termite activity in that area, the engineers were concerned that there might be significant structural damage in the wall. They told us that there was only one way to find out: to look beneath the plaster surface.

Prep work, as viewed from bimah:
Marking the locations, and placing air purifiers to catch plaster dust.
(As usual, click/tap on a photo to enlarge it.)

This past week, we finally undertook that adventure in discovery. Although the board had approved this work in May 2021, it took until now to arrange for the proper alignment of funding and expertise. Careful planning (described HERE) was needed to ensure that we would get useful and reliable answers to our questions, given our limited budget. 

This post reports on what was done, and the initial findings.

Executive Summary

In the first phase, a contractor cut five holes in the wall. That same day, we received visits from three parties: a waterproofing consultant, a structural engineer, and a termite inspector; they came to examine what was visible inside the wall. Their initial findings were encouraging: the situation was not as bad as many of us had feared.

In the second phase, plaster was removed at the base of one of the posts that supports a tie-rod. This step has confirmed that the post is still well supported, despite significant cracking in its exterior pilaster. (This should enable a repair of the pilaster to proceed without needing to shore up the post first.)

Phase I:  Five Openings

Cochrane Construction, a general contractor, cut five holes in the wall, after building a temporary coccoon to contain the dust. 

View of openings after the dust-catching bubble was dismantled.
For reference, the cuts are numbered 1 to 5, from left to right.

Then we received visits from a waterproofing consultant (Cameron Figgins of Absolute Maintenance and Consulting), a structural engineer (David Dorier-Sammut of John A. Martin & Associates), and a termite inspector (Jesus Tapía of Higgins Termite); they came to examine what was visible inside the wall. Their initial findings were:

• Minimal structural damage was observed in the vertical wood frame members and the horizontal sill plate. We saw no evidence that structural repair work is needed in that wall. No dry rot.

• An anchor bolt was observed, holding the sill plate to the foundation wall. Due to the prevailing practice when this building was constructed (74 years ago), we had not expected to see any such bolts. They are important for seismic integrity. Seeing that bolt was a pleasant surprise.

• We solved the mystery (described HERE) of the nature of the posts that anchor the tie-rods (which in turn help to support the roof). The posts are made of wood. (The steel surface that had been observed through a small exterior test hole a few months ago, and presumed to be part of an I-beam–shaped post, was actually an anchor bracket for the wooden post.)

• The observed tar paper (vapor barrier) is in surprisingly good shape almost everywhere. This tells us that the stucco system and the foundation wall can still be successfully waterproofed from the outside, without their needing to be replaced.

• Active termite infestations were observed in 3 out of 5 holes. Treatment is recommended before closing up the holes permanently.

Close-up of termite frass next to main post (cut #4).
Local tear in the tar paper has been admitting rainwater, which dampened the wood.

Close-up of sill plate that is bolted to the concrete foundation wall (cut #5).

Cut #2

Cut #5

10"-wide wood post in cut #4, at site where termite activity seen in wall in 2021.
(Post is anchored by steel brackets and sistered by 2" framing pieces.)

Anchor bracket at base of post, after termite frass vacuumed up.

The exploratory holes are now being covered temporarily—i.e., for several months—with fitted drywall pieces.

NEXT STEPS.  We await, and will assimilate, an updated wall waterproofing estimate, as well as formal engineering and termite reports. Then we will weigh our next steps. 

The tentative target date for a termite treatment is January 6th (when the inspector is already scheduled to return to our premises), assuming that we can agree on a fair price for treatment, and that the expenditure is released by the president and treasurer.

Phase II:  Plaster Removal from Foundation Wall Under Post

Upon request from the structural engineer, our custodian Ruben chiseled the plaster away from the base of one of the posts. 

This step suggests that the post is still well supported by its foundation, despite significant cracking in its exterior pilaster.  

Damaged pilaster base — the same post exposed by interior cut #4.

Damaged pilaster base after stucco has been chipped away,
revealing apparent rebar corrosion (which causes concrete to spall off).

This finding should give us the confidence to proceed with a repair of that pilaster, without needing to shore up the post first. I’m waiting for the structural engineer to confirm this conclusion. More to come on the planned repair of this pilaster.…

Acknowledgment

Special thanks are due to Ruben Carrillo; without his drive and skills, carrying out this project would not have been practicable. I’m especially grateful that he stepped into the breach when, just as the general contractor was arriving at the synagogue, I learned that I needed to be staying home in isolation.