20-year-old building – Spalling limestone

[Mike Lamb]

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

[Marc]

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

[Bill Kibbel]

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]

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. 

[mgbinspect]

On 5/22/2020 at 2:56 PM, Bill Kibbel said:

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.

Raked joints for the limestone was probably a bad choice and contributing factor as well permitting water to rest on and soak into all sides of the limestone. What a shame.