20-year-old building – Spalling limestone

[Mike Lamb 65]

Would sealing the exterior of the limestone blocks slow deterioration? Or would block replacement be the best remedy?

[Marc 88]

I'm curious about the efflorescence.  Why does it seem to favor the border between the spalled and un-damaged areas?

[Bill Kibbel 82]

If a lime mortar would have been used, the moisture in the wall would migrate out through the joints.  Portland based mortar is forcing the moisture through the face of the stones. 

Sealing on the exterior would be useless.  When the faces of the stones erode back about 1/2", they can be patched with Lithomex, which is lime-based.

[Jim Katen 153]

10 hours ago, Marc said:

I'm curious about the efflorescence.  Why does it seem to favor the border between the spalled and un-damaged areas?

Just a guess, but I suspect that the worst of it occurs where the most water emerges. You can't see it because it's fallen off along with the face of the stone.