parging a lime based poured concrete foundation?


Old 08-07-16, 07:25 PM
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parging a lime based poured concrete foundation?

Hi There:

I live in Toronto, Ontario. My house has a poured concrete foundation. The house was built around 1925.

While doing other work, I decided its time to repair the parging on the wall above and a little below grade. I removed 2 layers of parging done by others before me.
The one below the outer was actually not in too bad a state, the outer one had bubbled and was hollow under was only hanging on by the wire mesh which had been nailed to the wall.

After a bit of research and tossing of vinegar on the wall, (sizzled like a steak on a hot grill) I'm pretty confident the foundation must be a lime based mix of some sort. From what I understand I need to add lime to the parge mix to ensure it works well with the existing?

Is anyone able to offer some advice on the materials and ratio of the mix?

I do have on fairly good authority that I should use brick sand as one of the ingredients.

Thanks, Terry
Old 08-07-16, 08:07 PM
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Not sure what products are available in Canada, but here in the US some of the box stores sell Quikrete Stucco mix base coat and finish coat. Its basically premixed with sand, lime, portland, etc. at the right ratios for your base coat. You can apply a bonding agent first, or a dash bond (slurry) coat. Then apply the base coat about 3/8" thick. Once it cures, a finish coat (slightly different product) 1/8" thick.

You will want to neutralize that vinegar first with a good rinsing.
Old 08-09-16, 10:06 AM
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I don't know about foundations in Canada in 1925 but I don't think the poured foundation is lime. Lime does not have the strength you want for a building. Could it be limestone?
Investigate further. If indeed you have a lime based foundation and if you want a durable coating you have a couple choices
first you can use metal lath and nail it to the wall then use ordinary stucco for a coating. It is Portland cement, lime and sand or Plastic cement which you use without lime. The lime is a plasticizer and makes the mix more workable. There are some good videos about stucco if you nose around. There is one potential problem and that is that the lath will rust out below the grade. Galvanized lath will last longer than black painted but it will go too.
If you truly have a lime based foundation a good bet would be to use lime plaster for the parge coat. That vinegar you used: mix about a 50/50 solution with water and scrub all the old loose stuff off that you can, rinse then apply the new parge coat.
Mix some hydrated lime and mason sand about 50/50 then add water to get a spreadable consistency. The advantage of this is that lime is self healing. If it cracks some of the lime leaches out of the coating and fills the crack thus alleviating moisture penetration. This may have to be renewed every five years of so. Look for any loose spots, remove them and then mix clean it with a weak acid solution and apply again about the same way. If you leafe the first coat too smooth then mix up some lime and no sand and brush it on. Or look on line for some formulae for whitewash and use one of those. I use white Portland and lime for a whitewash over Portland cement plaster. since you don't think you have Portland cement concrete you should not use much if any Portland in the mix. There is a rule of thumb that says you should not put a harder, stronger material over a softer, weaker material. If you have a lime based foundation you have the softer, weaker material so use something that is not as hard or strong as a Portland cement material.
Again, check and see what you have for a foundation. The fizzing of the vinegar might have been alkali from the soil reacting with the vinegar not the base material reacting.
Old 08-17-16, 03:58 AM
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Thank You for the informative replies, I appreciate it. Looking at the calendar, with great reluctance, I'm going to need to bring in some professional help. There are too many other parts to this project that need attention and finishing and something has to give, so I think it will be this portion. Only so many hours in a day....


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