Step-by-step approach to waterproofing the steps: Part 1 of 3

THIS IS AN UDPATE of a post from 2½ years ago, “Water Intrusion Under Front Steps — Not Yet Stopped,” in which I described a longstanding issue that has been progressively moving up our list of priorities, until it has become currently our most urgent one. The problem can be summed up like this:

During heavy rains, our historic sanctuary’s front steps leak water, which soaks the concrete substrate below the steps, which in turn drips water onto the ceiling of the rooms beneath it in the basement.

Front steps at the 1948 dedication of our sanctuary.
(As usual, click/tap on an image to enlarge it.)

Back in 2022, I was stymied regarding a long-term solution. Contractors had made various suggestions, none of which were practical (such as “rip out the sandstone, waterproof the substrate surface, and then reinstall the sandstone”).

Then in May of this year, I wrote about the problem again because I thought we were close to engaging a certain vendor who had touted a particular sealant called Creto DPS. On that basis, the board agreed to authorize this project “as funds become available.” Now, Creto DPS does seem to be a much better and more permanent sealant than what masonry contractors typically apply to flagstone. However, that vendor flaked out—which in hindsight is fortunate. Why? Because I have learned a lot since then. Now I am preparing to do things rather differently.

Perhaps I still have a lot to learn, yet it finally seems as though a resolution is at hand. The right combination of expertise, materials, and funding may be coming together. Below the jump, I discuss the first of the three steps involved.…

Step 1:  Structural Repair

Here is what Guillermo Groisman (retired architect and general contractor) told me in a voicemail on Sept 3:

The concrete underneath the stairs is in very bad condition, so I suggest that you try to fix it first, before you seal the stairs from above—because otherwise the weight of the people walking on the stairs will deflect the concrete, meaning that the surface will crack again in the future, and the newly sealed surface will leak.

Previously I had not considered that my focused efforts to waterproof from above might literally be undermined by not attending to the concrete repairs first. (Rather, I had imagined it best to waterproof from above first, in order to keep the concrete as dry as possible, to minimize the ongoing structural damage.) But upon reflection, Guillermo’s warning seemed plausible. 

But then what exactly should be done, in the way of repair? I asked the estimator for our waterproofing contractor if he thought they could handle it. (They were already working on site. That company has a Concrete-Related Services license [D-06], which qualifies them to do “concrete restoration” but not “the installation of reinforcing steel.” I.e., they are not a full-service Concrete Contractor [C-8].) After looking at the degraded spots, the estimator said they didn’t look bad to him, so he offered a repair bid:

Concrete restoration: scope of work   

Hand/mechanically chip out all spalling loose/damaged concrete at the interior bottom side of the front entry staircase. Prime any corroded areas using Sika Armatec 110 primer, and re-build all areas using Sika VOH.

Those are indeed the highest quality materials. Their specialist was experienced and had already shown himself to be highly skilled, with regard to another repair on our premises. And this approach was similar to what another (more expensive!) vendor had done for us last year, on the exterior of the south wall. So this offer seemed promising.

Yet out of an abundance of caution, I reached out to Jim Farasatpour, a structural engineer who is a concrete maintenance expert (and a friend of Mishkon). The timing happened to work out, such that he could promptly make a site visit. Upon seeing the damaged spots today, Jim agreed with Guillermo that repair work needs to be done underneath the steps, before we attempt to seal them from above. 

Jim also told me that indeed most of the spalling and exposed rebar can be patched in a simple and straightforward manner, just as the waterproofing contractor had offered to do. However, two of the damaged spots require more extensive and specialized treatment. Here is the worst of them:

(The steel reinforcing bars should not be showing through the surface of the concrete—and they should not be rusting away!)

Jim said that he will write up the specs for that repair work, which I can then use as the basis to get bids. And he knows a qualified contractor who may be willing to do it.

He added, “Don’t feel bad about the state of this concrete. It actually looks pretty good for a building of this age that is so close to the ocean. I have overseen the same type of repairs at LAX. It will not involve major reconstruction.”

Finally, he commended us for attending to this matter before the degradation had gone too far. The substrate under the steps is more structurally significant than were the degraded spots along the south wall, so it warrants prompt attention.

To be continued with steps 2 and 3, in future posts.…