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hohadcr 09-13-2012 05:07 PM

1912 lime mortar?
I have a brick facade that is built in 1912 and it needs repointing.

The joints are very narrow, about 1/4 inch.

Someone told me anything before 1920 will be lime mortar, is it true?

The foundation of the building is puored ciment... built in the same year! Does that mean ciment mortar could be used for joints in that year as well?

So, to sum up my questions:
1. is the mortar definitely lime mortar because the wall was built in 1912?
2. if the year of construction is not sufficient evidence, how can I tell if it is lime mortar?

Thanks all.

dakzaag 09-14-2012 06:28 AM

Lime mortar is usually softer and more white than Portland based mortar. Depending on where you live, I would think it is most likely lime mortar.

I have heard the you can test lime mortar with vinegar. Supposedly if a flake of lime mortar is dropped in a cup of vinegar it will fiz like an alkaselter tablet. I have no personal experience with this test, I can usually tell lime mortar just by looking.

Ask a mason to look at it and he might be able to tell if he even knows what lime mortar is.

Daniel Holzman 09-14-2012 08:26 AM

Lime mortar is the original mortar mix, which I believe was set forth by Vituvius of Rome around 0 BC as one part water, one part lime, one part sand. This mix was used for thousands of years, and is still in use for historical renovations, and in Europe and other parts of the world that did not universally adopt cement based mortars, as did the United States.

Lime based mortars are relatively soft, and flexible enough that they can self heal cracks. They are effective when used with relatively soft material like brick, but can also be used with stone. Cement based mortars set quickly, are very strong, but in many cases are too strong for the materials surrounding them. For example, cement based mortars used with brick can crack the brick if the mortar expands, since the mortar is typically stronger than the brick. Lime based mortars will not do this.

As for testing, you can take a sample to a lab that tests mortar, they can tell you definitively what you have. I would not necessarily assume that you have lime based mortar based strictly on age, since modern cement based mortar was invented in the late 1700's (patented in 1824), so it is entirely possible you have cement based mortar.

tony.g 09-14-2012 02:41 PM

1 Attachment(s)
Just to elaborate on what Daniel wrote about the strength of modern Portland cement mortars.
Attached is close-up pic. of a garden wall just round the corner from me, which was recently built using late-nineteenth century reclaimed hand-made bricks, but using Portland cement mortar. The mortar forms a very strong bond with the brick but also shrinks slightly, and in doing so cracks the bricks right through.
The rule is that the mortar should always be softer than thebricks/blocks/stones being used.

hohadcr 09-15-2012 02:58 PM

ehhhh, asked several mason guys, only one said could be lime and told me if all depends on when the building was built....

Lab? (God bless this Quebec town.... ) I will probably send it out of province for testing...

Also, where can I buy Lime mortar? HD doesn't have it here.

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