Our back steps have seen better days. They are made of brick and probably lime mortar. Some mortar is missing, other parts are cracked or eroded. My DH wants to do repairs before another New York winter does more damage.

So my question is what is the recipe for lime mortar in the '20s. I can see little stones in the mix if that helps. We've heard of lime putty but can't seem to find a source. Could we use another type of lime? How hard is this task for a moderately skilled DIYer? Any other tips would be appreciated. Thanks.