Water Intrusion Under Front Steps — Not Yet Stopped

FEW PEOPLE ARE AWARE that our sanctuary’s front steps sit atop a portion of the basement. Until now, probably even fewer have known that whenever those steps get wet (from rainfall, or being hosed down, or washed), water percolates through and finds its way onto the ceiling of the rooms beneath. 

The results of this intrusion? They include: rusted rebar, spalling of the concrete, degradation of basement wall surfaces, damage to the ceiling drywall, discoloration of ceiling paint, dripping of water onto the floor, and potential dry rot in the ceiling joists.

In this post, I will discuss the nature of this problem, our attempted resolutions, and my plans for future action.

Description

Here is a plan view of the sanctuary’s front, from the 2003 Historic Structure Report (“HSR”). (Orientation: Main Street is to the left.)

Most of the leaking water is directly above both the lower Ladies Lounge and what I call the Basement Storage Room (accessed through that lounge). Here is a plan view of the basement rooms at the front of the building.

(The HSR labels the latter the Sump Pump Room, presumably because its most prominent feature is a large pump assembly in the middle of the floor. According to member and plumber Barry Steinberg, however, it’s actually not a sump pump but rather a sewage ejection pump. For decades, it has been disconnected and inoperational. Presumably after the city put in a sewer main along Main Street circa 1960, this pump was no longer needed to bring effluent up from the basement. It’s now a neglected, hulking piece of equipment — covering a pit in the floor.)

As for the attic crawlspace above the basement rooms, its “floor” consists of the ceiling joists of the rooms below. (Attached to those joists are panels of perforated gypsum board, used as a support for a plaster finish coat, as the ceiling of the rooms below.) Its “ceiling” is the underside of the stairs, which is obviously angled acutely, with transverse concrete beams. As the HSR noted briefly,

The entrance stairs are reinforced concrete stairs spanning between concrete basement walls, leading to a concrete landing at the entrance portico.

This crawlspace is accessed through an opening in the ceiling of the storage room. (Presumably the similar opening in the closet of the kitchen likewise provides access.)

From the perspective of facilities maintenance, the basic challenge derives from the physical fact that concrete is porous. Water that migrates into it can cause the reinforcing steel bars (“rebar”) inside to rust. Rusted metal takes up more volume than raw steel. So the expanding metal cracks the concrete, which leads to spalling (concrete breaking off in fragments). 😳

The management goal is to keep the concrete dry. Otherwise, over many years, the structural integrity of the steps will eventually become compromised. In theory, this means making sure that the top surface is watertight. In practice, this is easier said than done. Unfortunately, untreated sandstone (i.e., the flagstone) and its grout (especially cracked grout!) is highly permeable to water. The surface needs to be kept chemically sealed, but that apparently hasn’t been done in recent years.

In 2005, the Building & Grounds Committee commissioned a water intrusion inspection report. The 2 pages that describe and document the aforementioned leakage at the front steps can be viewed HERE.

Since that report was issued, some cosmetic repairs have been made; and Ruben Carrillo, our intrepid custodian, has placed more than half a dozen aluminum pans atop the joists, to catch drips. Below are photos he took last October, each showing dripping concrete and a pan below.

Following a heavy rain in January (after Ruben had left on his annual family leave), I observed that those pans were pretty full. And water had been dripping onto the ceiling of the Ladies’ Lounge, in a spot where there was no drip pan.

The HSR (p. IIC-20) makes the following assessment and recommendations, which it labeled a high priority:

Saltation is observed on the underside of the concrete structure under the west steps and portico floor. The concrete structure is not compromised, but rebar jacking could destroy the integrity over a long period of time. Treatment alternatives, in order of action: (a) add a waterproof membrane at the bottom of the west entrance planters in order to prevent any irrigation or rain water from percolating into the ground and structure; (b) if moisture intrusion continues, remove flagstone paving, cut in site drains, add a waterproof membrane and joint sealants, and reinstall flagstones over the improved substrate.

Is significant rainwater coming into the basement from the planters? Well, I have my doubts. Given that most of the dripping water seems to be coming from near the middle of the stairs, and not from near the side planters, I have not rushed to dig out those planters and install a waterproof membrane therein. (This may perhaps have been done since 2003, although none of the former B&G members I’ve spoken with is aware of such an effort.) Also, I’ve noticed that when Ruben waters the plants at the front portion of the southern planter, liquid promptly drains out the front spouts at the bottom of the planter and onto the flagstone pavement near the sidewalk.

Attempted Remediation

One reason for our doing the Flagstone Remediation Project this fall was to recondition the steps well enough to be able to apply a penetrating sealant as the final step. After consulting with a water intrusion expert who was recommended to me by the then co-chair of the B&G Committee, Spencer Rosenhack, I asked our masonry contractor to apply Lifeguard® Waterproofing Sealant, which is invisible and carries a 30-year warranty (in contrast to the 2-year useful life of most commercial penetrating sealants), although it involves some extra effort and care in application. Unfortunately, he refused, preferring to stick with the sealant that he was familiar with — even though I offered to pay the difference in cost. I then looked into having our consultant apply the Lifeguard product instead, but he wasn’t available.  

So we went ahead with the standard 2-year sealant applied by the masonry contractor in early November. My hope was that it would substantially reduce water penetration through the steps into the crawlspace; and we waited with anticipation for rainfall, to see what would happen. According to Ruben, however, the water intrusion is not noticeably better this winter. Ah, we tried! 😖

Possible Next Steps

Now that our water-intrusion consultant seems to be more available, he has given us an estimate for applying Lifeguard to the steps (only). Given what he and I know about this product (such as its unusual ability to fill in small cracks), it promises to reduce intrusion a great deal. I intend to contact the manufacturer’s technical consultant (listed on their website) and ask for advice, too. 

Hopefully before the next rainy season, there will be sufficient funds to pay for this treatment. (By dealing meanwhile with water intrusion in other areas, we have already used up the board’s 8/8/21 budget allocation for measures to control water intrusion.) At the very least, when the existing sealant needs to be replaced in 2 years, we can apply Lifeguard then. (One application of Lifeguard costs about 3 times as much as the generic sealant, but it lasts 15 times as long!)

I’ve also received a separate estimate for applying a Xypex sealant to the underside of the concrete stair bed, in case the Lifeguard doesn’t work as hoped. Our consultant says that Xypex would stop the dripping of water onto the ceiling below. However, it's not cheap; and that fix may create new problems of its own. (What would become of any water that penetrates into the concrete from above? Where would it go? I don’t water to be marinating the rebar! Presumably the water would make its way downhill to where the steps’ concrete meets the foundation/basement wall. What is at that joint? It’s hard to tell because it is so inaccessible. Is there a wooden sill plate between those two structural elements? And how are the joists are anchored to the west wall? Such questions would need to be addressed.)

Meanwhile, I personally look forward to Ruben’s return to Mishkon, so that we will again have reliable and regular observations as to what’s going on in the crawlspace. He’s very conscientious about such aspects of our facilities. We owe him our gratitude. This situation would be much worse if not for his interventions along the way! 😎

Update 7/18/22

To be on the safe side, I called the manufacturer of Lifeguard® Waterproofing Sealant and discussed our situation with their technical consultant. Good thing that I did, because he actually did not recommend that product for our purposes, for several reasons.

1. By its nature, sandstone is too unstable to enable an enduring waterproof seal. As pieces of it weather and occasionally flake off, the newly exposed portion of the surface will be left unsealed. And it will have a slightly different color than the sealed area.
2. The penetrating sealer that was applied last November is likely to interfere with the new sealant.
3. This sealer can fill fine cracks (up to 1/16" wide) but not the broader cracks that can develop between stones and grout.

So at the moment it appears that we must live with the ongoing water intrusion, while reapplying a generic sealant every 2 years to the flagstone, to at least help preserve the flagstone itself.