GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Can I stop the water from seeping through concrete block?

Sawdustmaker63 | Posted in General Questions on

I have a concrete block column that supports an overhang. There is a concrete cap over the top of it where it is otherwise exposed. I have sealed the gaps between the two. There is water seeping out of the column several feet up from ground level. This column is free-standing, so the water can only be coming from the top and sides, unless it is somehow squirting up from the ground (doubtful). The column is in front of a south facing block wall. Does anyone have any ideas for curing this? Rather than fluffy effluorescence, the residue is hard calcium carbonate like a stalagmite. I chipped about 1/8″ of the stuff off of it before painting. The fresh paint did not stand a chance against it.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. GBA Editor
    Martin Holladay | | #1

    Does liquid water flow from the mortar joints? Or are you just seeing the efflorescence?

    Can you post a photo?

  2. Sawdustmaker63 | | #2

    There is actually liquid water coming from the mortar joints. Since the surface is freshly painted a photo will only show the tracks of the water running down the face. Prior to painting I removed patches of calcium carbonate scale that were probably over 6" across. This has obviously been going on for some time.

    I am curious about how the water is coming into the column. If I can stop the ingress there will be no water available to leak through the mortar. My examination showed no obvious openings at the top of the column. I have never seen this happening before. The column is freestanding. We are also seeing holes rusting through a steel door frame on the building. The roof flashing appears to be intact around the perimeter of the building. The problems are unrelated, but could they have a similar cause as far as how the water is getting in?

  3. GBA Editor
    Martin Holladay | | #3

    Without a photo or a site visit, it's hard to diagnose the problem. It's not unusual for bad roof flashing to look good at first glance.

  4. Sawdustmaker63 | | #4

    Thanks for your consideration.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |