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Type or Parging & waterproofing for old concrete foundation

Good day,
My house is located in Toronto, Canada, built in 1912 from brick. The foundation is poured concrete. It is fairly soft and I believe its made mostly of lime, as that is what is used for the mortar to lay the bricks. The side of the exposed foundation was parged over likely a few decades ago with what appears to be a very hard portland cement. The lower half of which is loose and sounds hallow. In other areas, the concrete of the foundation is crumbing about 1 ft above grade. Inside the basement, there is trace amounts of moisture and the foundation is flaking. I am going to have the entire perimeter excavated, the old parging removed. I was planning on patching in damaged areas / forming up as necessary the parging down all the way to the footings, then doing waterproofing. My question is what kind mortar do I use. All the contractors who have looked at the house (about 10 of them now) are planning on using a pre-mixed parge mix. I think this is going to cause similar issues to what is occurring now- the old porous lime based foundation whicks up water from the ground and the parging traps it in the foundation. With no where to go it pushes the new portland cement parging off the wall. Is there any disadvantage with using a mix of sand and naturally hydrated lime?

Asked by Michael Genin
Posted Jan 17, 2013 2:42 PM ET

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2 Answers

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1.

Michael,
I suggest you read this article by Joe Lstiburek on sacrifical parging: Efflorescence = Water Damage.

Answered by Martin Holladay, GBA Advisor
Posted Jan 17, 2013 3:04 PM ET

2.

I certainty did read that, and a lot of the responses below. Most seem to be with regards to brick or stone foundations. I'm assuming that the same applies to poured concrete. If that is the case, we I'm assuming that using portland cement is the wrong choice.

Answered by Michael Genin
Posted Jan 17, 2013 3:19 PM ET

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