Limestone Erosion

When there’s significant erosion to a 100 year old limestone wall, should that be evaluated by an SE or foundation contractor? What is usually done to rectify/prevent the ongoing erosion process?




From the one picture, there does not seem to be much, if any, deterioration of the actual stone but the joint mortar is failing from longterm soil moisture over the 90-100+ years of its life. The efflourescence is evidence of the slow moisture movement inwards.

If it’s no worse than that in other areas, I’d recommend a mason with experience in stone foundations to clean out out loose mortar and re-point the mortar joints.

Thanks Brian.

Some exterior waterproofing is also in order. Seems like the old parge has failed.

I see this alot. Older limestone, rubblestone or brick foundations, but the grading, bad downspout drainage or other exterior factors change and the foundation gets more water than it did before.

In Chicago, where they no longer allow downspouts to drain into the sewers like they used to, the downspouts now just drain against the foundation. That leads to this, or so I have found.

What has changed? That is usually the cause of the problem.

No visible exterior drainage issues with property. Perhaps this may be the result of 100+ years of soil wicking?

Where were downspouts taken to and how far were they extended?

How about the adjacent houses? Are they dumping on the property?

Could be just parge failure. Gould just be that we have had 2 warm, wet winters. (Most foundation and brick veneer drying takes place in the winter, around here).

BTW: I tell ALL my clients to get a basement dehumidifier and run it all the time, except in winter.


It’s quite interesting to see the effects of 70-90 years of constant moisture diffusion through early concrete walls. I have seen crystalline efflourescence structures 1"+ out from the wall and up to 3/8" to 1/2" spalling of the inner concrete wall surface.

I see that exact condition often in older houses in Denver and it always appears to be connected to moisture… sometimes intrusion, but often also related to high humidity related to poor venting of older heating systems

Think you’re a bit off base on this last reason. Are you also having air quality or high CO concerns in these same basements?

BTW, if there was high RH in these basements mould/mildew issues should also be prevalent. Also, with high interior humidity the moisture movement which brings the efflouresence salts from the mortar/soil would be less due a lesser vapour pressure/saturation between the soil, wall and the interior air.

I did one about a month ago that looked similar to that and it was worst where the furnace had been for along time. Parge coat gone. Furnace and water heater vented into the old chimney which was capped off. All exhaust gasses blew directly back into the basement bringing a lot of moisture with it, but there was mold too.
I think typically it’s intrusion from drainage issues, though.