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I've read that one should use a special type of mortar with old brick houses because they expand more - portland mortar vs soft lime.

The recommendation from the NY Landmarks Commission states:

Use a soft, lime-rich mortar that will be elastic and allow for movement, which will help prevent spalling and breakage of historic brick due to expansion caused by water absorption.

https://www1.nyc.gov/assets/lpc/downloads/pdf/pubs/App_Guide_Restoring_Arch_Features.pdf

I might possibly need to submit a permit to do this small repair.

If I need to repair some small sections of mortar to prevent water and ice getting in - should I use commercial regular mortar repair tubes or should I get an acrylic-based or some other special mortar repair product? Is the section small enough that I don't need to worry about matching expansion rates and sand color? It looks like this small section was already repaired more recently and doesn't have matching color mortar. Was using the wrong type of mortar the reason it's cracked?

The cracks are not huge - pictures shown below. Could I even use non-sanded grout repair material?

enter image description here

Cracks around mortar at knee level around the 1st-floor main exterior doorway (up a set of stoop stairs)

Cracks around mortar at knee level around the 1st-floor main exterior doorway (up a set of stoop stairs)

Front on shot of the cracks near doorway Front on shot of the cracks

Some mortar cracks between my house and the next adjoining house. Should I use different mortar for the cracks between my house and the next door house? Some mortar cracks between my house and the next adjoining house

  • Is that brick facing? Or foundation, trying to understand if you may need need a stronger mix. – Ed Beal Sep 16 at 13:57
  • Not sure what you mean by brick facing - but it's facing front on in the 1st and last pictures, while the 2nd picture shows it around a door jamb. The whole location is on the 1st-floor entryway above grade at the top of the stoop. – MonkeyBonkey Sep 16 at 15:01
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    @EdBeal Added a wide shot picture with a circle around the affected area for reference – MonkeyBonkey Sep 16 at 15:09
  • It should be brick facing – MonkeyBonkey Sep 16 at 21:55
  • Grout is just Portland cement with a color additive. 100yo building: you need actual mortar with hydrated lime. @EdBeal, +1. – Mazura Sep 17 at 2:32
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With a facing I would clean all the loose out and mix some but I have the lime and bags of clean sand and pick up some fresh cement. Since you are new to this I would suggest a pre mixed repointing mix. It is a little more expensive than mixing it up your self. Pre mixed is basically Portland cement, clean fine sand, hydrated lime, and water, I will use an add mix it helps to seal but I don’t know if it is necessary, I started using addmix after learning how to tile. The reason I asked about foundations is then a stronger type (n or s ) would be needed. For exterior above grade any grade n, s or m will be fine. But purchasing a premix just go to a big box store and find the pre- mixed repointing bag. Add water according to the instructions better to start with not enough water and work up. There are acrylic? Premixed that you put on and let dry but I have not used these some one else may have advice on them.

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