Mortar Confusion: type N, S or something completely different?

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  #1  
Old 03-31-18, 10:23 AM
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Mortar Confusion: type N, S or something completely different?

I have been doing minor brick tuckpointing repair using Quickrete Type N. I am now moving on to some areas in our stone foundation and am very confused as to what mortar to use. Some say itís ok to stick with Type N... others not so much. Some spots that need attention are exterior, some interior.

Below are a few photos. Note that a previous owner did some (not so pretty) fixes to the exterior abt 20 years ago. They seem to be holding up fine & we would rather not redo if possible. Also, we arenít too concerned about aesthetics.

Under these circumstances.... Is it ok to stick with Type N? Or?

Thanks in advance!
 
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  #2  
Old 03-31-18, 01:57 PM
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It was my understanding that if you spell the word M-A-S-O-N that the further you go to the right as you spell out the word, the stronger the mortar is. So type N is stronger than type S. Stronger mason is for larger building projects. So, if that is what you already have, then continue to use what you got.
 
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Old 03-31-18, 02:16 PM
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czizzi -

You have the order of the strengths reversed. As you move from left to right, the strength decrease. - Type M is the strongest and Type N is the weakest.

Type M has the highest strength, followed by Type S and Type N IF you are interest in compressive strength.

There are reasons for the use of the various types. - The ASTM mortar specification (ASTM C270) states in the Appendix that the weakest strength to carry the structural loads should (not must) by used. The workability of the mortar is a very important.

For high strength walls, the mortar strength is not limiting factor since it is just a narrow layer. - The masonry unit strength governs,

The decade old question is "Does mortar hold masonry units together of keep them apart?"

Dick
 
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Old 03-31-18, 02:35 PM
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Thank you, I stand corrected and my memory from many years ago recollected wrong.
 
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Old 04-01-18, 03:44 PM
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That’s a good tip! Will keep it in mind.
So, I am thinking that means N (the weakest) would be good for our 100+ year old stone foundation.... Right? So the stone doesn’t get all of the harsh effects of weather/water. This is the part that I keep getting confused/different info on.
 
  #6  
Old 06-09-18, 05:50 PM
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There are many factors involved with choosing a mortar type for repointing. One is to match the strength of the mortar to that of the material being repointed: mortar that is too strong can cause spalling of the substrate. You may consider the opposite to be true. I have used the quikrete and other pre-mixed mortars, and they are particularly lean, not sticky, often difficult to work with. For your project, if color or the sand/aggregate is not an issue, go with your quikrete product, add lime or Portland to create the desired workability, and be sure to clean stone first of dust and dirt. If is important to cram the voids as full as possible with the proper tools, let the mortar set to allow you to treat the joints to your liking.
 
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