Bricks, Masonry, Asphalt and Concrete - Old mortar mix proportions

I live in a 2 story brick house that was built about 1853. In some areas you can rake the joints with your thumb and sand falls everywhere; in other areas where joints aren't crumbling, there's a thin layer of what I guess is red paint that has protected the mortar. At the very least I'm going to have to repoint the crumbling joints. I've heard that old mortar mixes (and this is what I understand you should use) are just hydrated lime and sand mixed with water, but I don't know the proportions. Would appreciate any help with proportions and any thoughts on whether I should repaint after repointing. Thanks.

[QUOTE=bren]I live in a 2 story brick house that was built about 1853. In some areas you can rake the joints with your thumb and sand falls everywhere; in other areas where joints aren't crumbling, there's a thin layer of what I guess is red paint that has protected the mortar. At the very least I'm going to have to repoint the crumbling joints. I've heard that old mortar mixes (and this is what I understand you should use) are just hydrated lime and sand mixed with water, but I don't know the proportions. Would appreciate any help with proportions and any thoughts on whether I should repaint after repointing. Thanks.[/QUOTE

If I were you I would use the pre-mix mortar mix you can buy, at building centers, the type you just add water to.

I am no chemist, but I am sure that if you mix sand water and lime, you will end up with a product that will look like morar, act like mortar, but will never, get hard.

I would mix a bit of this, mix up you say is an old mortar mix, and see if it does set up.

Thanks for taking the time to respond, Mowpar. I believe I will mix up a sample batch of lime and sand (found a reference to 1:3 mix of two) and see what happens. Apparently, the problem with any mix that contains Portland cement has to do with the Portland retaining too much water which eventually makes it into the brick and destroys it.

Do not use portland cement mix use mortar mix. portland is for concrete, not for the laying of brick.

Thanks, mowpar. If you look at the MSDS for one of the very common brands of mortar mix or mason mix sold at the large home improvement stores, you'll see that Portland cement is indeed an ingredient. If you do a search for "brick repointing" or "brick restoration," you'll come up with a number of helpful sites. I appreciate your interest, though; thanks again.

There seems to be a problem with the terms used.

I am not aware of a pre-packaged product called "Cement Mix". There is a product offered that is "Concrete Mix". It is a mixture of Portland Cement and aggregate (sand & gravel).

For mortar, there are a number of different types, depending on the desired application. The common types are Type M, Type S and Type N. All contain Portland Cement with the addition of varying amounts of hydrated lime and/or additives and admixtures. Type M is the strongest and Type N is the weakest. The rule of thumb is to used the wekest mortar you can because those mortars have some very benficial properties like workability, water retention (when plastic), water resistance, bond and long term healing (carbonation). All mortars do get "hard", but some are softer because of the lower compressive strength (not a problem). When in doubt, you Type S or Type N unless you have a wall over 10 stories or so.

The very old mortars used centuries ago and before the development of Portland Cement consisted of sand, lime and pozzolanic materials like volcanic ash. They are proven and lasted for centuries. The lower strength was not a problem because of the massive walls that were built. Sand-lime mortars have been sucesssfuly used for tuck pointing because of the adhesion and workability where high compressive strengths are not required.

If you really want to be confused look at ASTM C270 (American Society for Testing and Materials specification for mortar).