Q: basement waterproofing with sodium silicate?

[Len Budney]

Hello,

I'm taking estimates to repair my leaky basement. The house has four settling cracks, all starting at corners of windows and running right to the floor. Water pours in when it rains. The house has no external membrane or drainage system, being built in 1924.

Most contractors recommended "interior french drains" and crack repair using things like densicrete. Our latest contractor gave an interesting recommendation taht sounded more comprehensive, but I'd like to check whether he's talking sense. Here was his complete verdict:

1) Terra-cotta pipes under the downspouts need to be replaced. The contractor proposes to replace them with plastic pipe and fill the terra-cotta with cement.

2) Next he proposes to inject the interior cracks with epoxy.

3) Then--and here's the most interesting part--he plans to excavate the foundation to a depth of 18 inches or so, and fill the trench with dilute sodium silicate (waterglass). The waterglass is supposed to follow the path water would follow, and then harden, sealing the foundation cracks and any voids in the earth near the foundation. He projects that about 20 gal of this stuff, diluted with 500-1000 gal of water, will do the trick.

4) When the waterglass does its magic, he will use the 18-inch trench as a surface drainage trench by filling it with tile and rocks or gravel.

5) Inside, he will either (a) epoxy inject the cove all around, (b) put a couple of holes through the floor and install sump pumps, or (c) install a complete floor drainage system. This is specified to be at his option; he says he will do whichever is most appropriate to prevent any pressure buildup under the floor, and will not change his final estimate based on his decision here.

6) Also inside, at my option, he will install a vinyl material on the basement wall ("just like the inside of a refrigerator"), either halfway up or all the way up, or will paint the walls with chlorine-laden anti-mold paint. When injecting the cracks they will have cleaned the basement walls with muriatic acid and sanded as necessary.

7) Finally, he will paint the exposed parts of the foundation with a silicone material. If I want to fix up the peeling red paint first (!) then he will come back after I finish painting, and do that part then.

He asserts that this is better than excavating the full foundation and installing a membrane, because some system would still be needed in the floor, and the foundation was probably poured with no external form--so the outside would be an aggregate of cement, dirt and rocks with no workable shape or texture, making it very difficult to apply a membrane anyway. Against this difficulty he advocates his proposed solution as both effective and cheaper. The entire estimate sounded pretty fair--well below $10K--and includes a transferrable lifetime guarantee against further basement leakage.

The biggest question is, does his proposed use of waterglass sound right? I can't find much about this on the Internet--it doesn't look like many companies have latched onto his "secret" yet. Is this likely to work? Or is the epoxy injection going to stop my leaks, with the rest amounting to window dressing?

Any input would be GREATLY appreciated!

Thanks, Len.

[jitney]

Sodium silicate is an established way if reducing the porosity of concrete. I am doubtful if it would bridge more than a tiny crack, though. The epoxy injection has the potential to seal cracks if the technique is good and the cracks can all be found. The warranty is only as good as the outfit offering it, check references, BBB, and complaints against his contractor's license.-Jitney

[Lyle B. Harwood]

? I'm taking estimates to repair my leaky basement.

Water needs to be kept on the outside of the foundation.

Once water has penetrated the concrete, damage has already been done.

I wrote about here:

Occasionally, there is a house with a foundation that needs an engineered solution to keep it dry, but those houses are pretty rare. Nine out of ten times, standard dampproofing and drainage works just fine.

Best of luck, and let us know how it comes out!

[lbudney]

Thanks for this; it's the first negative reply I've gotten so far (not counting my father-in-law the petroleum engineer's opinion that it "sounds kooky").

The reasons I considered it plausible were twofold: (1) I have found references to sealing (fully exposed) foundations with sodium silicate, and (2) I've found references to the use of sodium silicate to manage sink-holes and similar problems by hardening the (preferably sandy) substrate. The most scientific reference I've found so far is at . Relevant snippets:

"Sodium silicate has been used extensively in the United States and Europe as a soil strengthener in unconsolidated soils (Voss et al.,

1994)."

"A minimum hydraulic conductivity of 10^-4 cm/s is required for the injection of microfine cements, montan wax, and sodium silicate grouts. In lower hydraulic conductivity soils (less permeable), grout tends to displace or compact rather than permeate the soil."

"Advantages: Low permeability, less than 10^-9 m/s (Roberds et al., unpublished)"

"Disadvantages: Limited to sand and gravel..."

Could be. I've asked for references to anyone other than this guy who uses the process (IIRC, he alluded to a Mil Spec, but I'm unsure). His assertion is that the stuff, having similar permeation properties to water, will go where the runoff goes, and then harden. While I see your point, he made it sound plausible...

But labor, backfill, etc., will increase the price. The overall job looks to be about half what it would cost to fully excavate, seal the outside, epoxy inject the cracks and add internal floor drainage.

I will take your advice, unless he gets back to me with substantiation of his method that I can verify.

Thanks, Len.

[lbudney]

Here's *a* relevant mil spec:

While it doesn't mention the "dump it against the foundation and let it perc through" process specifically, it gives some interesting claims; in particular, that a 30% silicate solution can be considered permanent despite subjection to freeze-thaw cycles, and that weaker solutions can be considered permanent when below frost and not permitted to dry out.

--Len.

[RB]

As I recall, Rutland was the company that I bought sodium silicate from in the 40s and 50s for preserving eggs. They may have moved into using the material for water proofing. Since they're still in business it might be worth asking.

RB

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