Proper ratio of sand to portland cement to use for repairing a 30 yr old stone wall

mortarpatiostone

I have a 30 year old stone 12" high stone wall that needs to be patched up.

There are small voids where stone has fallen out.

My question is what is the ratio of portland cement to sand used to set the new stones in the wall?

Is the ratio different for the mix used for the mortar between the
stones on the facade of the wall?
Thanks for your help

Best Answer

Since you asked it's 6 parts sand/1 part cement/1 part hydrated lime; it won't stick without the lime. Unless you absolutely need to use a specific sand you're much better off buying a bag of premixed mortar. You can take a piece of the existing mortar to a masonry yard and get a color matched dye if you need an invisible repair.

A helpful pneumonic device for mortar is "MaSoN wOrK." The capital letters represent the standard mixes in decreasing order of compressive strength.

  • Type M has the most cement and is used almost exclusively below grade.
  • Type S has the highest tensile strength and is used for outdoor load-bearing work such as retaining walls.
  • Type N, the 6:1:1 mix above, is used indoors and out for soft stone and brick work.
  • Type O is limited to non-bearing use indoors.
  • Type K isn't a thing anymore, outside of restorations. As you get to this end of the spectrum there's less cement and more lime so things are a sticky mess.

You'll find bags of Type S and Type N in the home center. You can use the same mixture all over the wall. I'd suggest N based on your description.

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