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Community and Q&A

What’s causing this brick to deteriorate?

GBA Editor | Posted in General Questions on
brick efflorescence.jpg

This photo shows a section about 3 ft. up from the ground of a brick column in the middle of the basement of my 1870s home.

The column is part of the base of an old chimney which was removed long ago. This section is all that’s left. It sits on a concrete floor and runs up to the bottoms of the floor joists. It looks as if at one time it supported a girder that catches the floor joists at midspan. But lolly columns carry that load now so the brick doesn’t seem to be doing any structural work.

I could remove it, but first I’d like to understand what’s causing the brick to deteriorate. The basement is damp so I definitely need to address moisture issues around the foundation walls. But this section of brick is in the middle of the footprint of the house so it’s not getting wet at all.

Any ideas what’s causing this?

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  1. Expert Member
    Michael Maines | | #1

    Chris, clearly a previous owner kept animals in the basement, who used the efflorescing minerals in the column as a salt lick.

    Just kidding. Usually this kind of damage is from moisture wicking up from the ground and dissolving minerals in the masonry, a phenomenon called "rising damp". The whitewash on the bricks above is actually one way of dealing with it. The lime-based whitewash acts as a sacrificial coating, which needs to be renewed periodically or you get the kind of damage you've found. A thicker parge coat is another option for a sacrificial coating. When bricks aren't fired hot enough they come out soft, and are particularly prone to this problem. (Bricks seem to be fired hotter and more consistently than they used to be.)

    It's curious how high the damage shows though. Around here it's usually closer to the floor. Your basement must have been pretty damp to allow moisture to wick that high. Or, it's at a height where the brick was saturated AND cold enough to freeze, but that seems less likely.

  2. Riversong | | #2

    Actually, in the 1870's the "thin-waisted" column look was de rigeur [also just kidding].

    I also doubt this is freeze-thaw damage, which is typically more chunky and flakey spalling. Definitely looks like osmotic deterioration from "rising damp", efflorescence and salt deposition. The salts left in the outer layers of brick after the dampness evaporates, then create osmotic pressures which can easily exceed the strength of the best bricks as well as the mortar in the joints. This is an outside-in kind of deterioration.

    As Michael suggests, the best defense is a sacrificial stucco or plaster coating.

    By the way, how did you post that picture?

  3. user-659915 | | #3

    This very curious. It seems to be a machine-made brick, probably tunnel-fired, which even in the 1870's was indicative of a fairly consistent quality - earlier batch-fired hand-made bricks varied in hardness according to where they were stacked in the kiln. You can see the bullnose corner chamfered out to a square corner at the top, an indication of craftsmanship which makes it unlikely that the original mason would have used a substandard brick for any part of the structure. I rather doubt this is the result of rising damp if there is not similar damage on the perimeter foundation wall which you would normally expect to be much more vulnerable to this effect. I suspect the cause may have been saturation of the brick from the interior of the chimney above, caused by chronic neglect of flashings and the absence of a cap. I have seen brick eroded like this on the inner face of a third-story exterior wall on an eighteeenth century house in southwestern England, much too high for rising damp. The cause in that case was undoubtedly chronic neglect of gutter and fascia.


    This is an interesting puzzle. Also painful because I think this chimney suffers from the same issue I had in a house I built about 15 years ago. I think the bull nose brick James refers to actually is a square brick with a spalled off corner, if you look at the very top of the image you see the least damaged corner brick has a square corner.

    But I do think the issue here is good craftsmanship combined with poor maintenance and I think the water that is causing the spalling is entering at the top of the chimney between the chimney cap and flue tiles and running down an expansion cavity between the flue tile and the brick chimney until it hits the point in the basement where the tumbling mortar or the setting of the lower course of tile has stopped the water migration and forced it to work out through the brick and evaporate causing the issues referred to by Robert and Michael.

    So my suggestion is to inspect the very top of the chimney for an entry path for water to get between the flue tile and the brick of the chimney. The house where I had this issue all those years ago we had a chimney-top damper on a wood stove with a sloped masonry cap on the top of the brick chimney which got saturated with water, froze and cracked allowing rain to penetrate into the expansion space between the tile and brick and effloresce inside the house. I don't remember the exact repair we did there but it probably involved making a decorative copper chimney cap that shielded the entire top of the chimney from rain. If you have a cracked chimney top parging then something like this will probably stop the water migration and allow you to repair the damage and not have to worry about it recurring.

    I think the key to the picture embed is in the input format under "lightshow" but not sure, I really wish we had a way to edit or at least preview so we could experiment with posting photos or Hebrew letters etc. All things in time I guess.

  5. Chris Ermides | | #5

    Thanks very much for your insights, guys. They're very helpful (and Mike - thanks for making me laugh. Salt lick - now there's some wit for ya).

    It is curious that I don't see the same sort of damage on the exterior foundation walls. Two sides of the house take on a lot of water (Yankee gutters are failing and grade doesn't pitch away from house sufficiently). I'm going to ask Dan to post a photo that I took of one of the walls. It'll be a separate question.

    Rising damp seems the most feasible since the chimney no longer exists - it was removed long ago - taken down to just below the first floor joists. There's soot or coal seeping out from part of this section as well. Not sure if that supports the rising damp theory, negates it, or is irrelevant. Just thought I'd mention it.

    To answer your question Robert about posting the pic - I actually didn't post it. Dan Morrison did it for me. Dan's in charge of this website - he works down the hall from me (I'm an editor at FHB). I promised to quit bugging him if he'd help me figure this thing out.

    Thanks again for your help - I know you're all busy so I very much appreciate you taking the time to read my post and respond.


  6. user-659915 | | #6

    I've seen a lot of rising damp issues (especially in England where few older buildings were constructed with a capillary break) but I've never seen this kind of damage as a result. This would take repeated freeze/thaw spalling, over many cycles and with the masonry really saturated. Hard to see that arising in the center of a basement.

    Here's another thought - stupid question maybe but I'll ask anyway: are there any signs of tool marks (pick or hammer) on the waisted brick? I can't tell from the photo. Could someone have started to demo the chimney butt and got distracted?

    Another question - soot and/or coal seeping out can only have come from the chimney above. Is there or might there have been an ash cleanout in the butt that could have been flooded at one time?

  7. Brent Lerwill, Brentwood Building & Home Inspections | | #7

    I have been a home & building inspector (not code) for several years and a general contractor for 17, and started my building career in 1966; and I've never seen a chimney quite like this one. That's what I love about this business: There's always something new to learn. It never get boring. I was raised on a farm in the mountains of Idaho and know about animals, so am inclined to go with the salt lick theory........;~). I also enjoy builder types' twisted sense or "humor".
    First of all, it is not possible to give a good answer to a lot of these questions without being there to see everything around it that might have affected this condition. I think, with the information available, all the causes already pointed out could be valid. It could, also, be a combination of all: wicking from below, moisture from above, brick quality, etc. I think it is a key piece of information that the soot and debris over the past 130 or so years could have easily built up in the bottom to the point where the deterioration has occurred. If this is true, the water coming in from the top due to no cap, cracks, flashing etc. ran down and then wet the soot at this point holding the moisture and causing it to escape through to the outside of the chimney brick. If I were there, another thing I would wonder about and look for is evidence of something having been built around the chimney at this level. This would have been a good height to have some kind of bench or shelf, or whatever attached to the chimney or just built against it. What did they store on this shelf, or what activities took place that could have caused mechanical or moisture related damage? Was the moisture migrating through the brick "attracted" by capillary action to the "dryer" wood and concentrated here, causing this waist area to be wasted faster? The final conclusion is that we can't really make a final conclusion with out being there, so, if you will fly me back there, I would be happy to share a beer and talk more about it.
    Brent, Oregon Coast, Where Moisture is always an issue.

  8. GBA Editor
    Rob Wotzak | | #8

    If you want to better understand one of the common forces that damages old masonry structures check out Joe Lstiburek's latest building science podcast about efflorescence.

  9. Expert Member
    Peter Yost | | #9

    What a great exchange on this one! I think the rising damps pretty much have it, but having little experience myself with this sort of masonry puzzle, I went to the rising damp master, BIll Rose. Bill is author of a pretty cool book entitled Water in Buildings, a really good read for those of you not familiar with it.

    Bill said several really interesting things about this picture:

    1. Usually, a pattern of distress makes you want to draw an arrow to the center of the distress, in this case the "waist."
    2. I compare it [rising damp] to paper chromatography, a neat way to separate constituents of solutions. Wherever rising damp occurs from water below, the top level is usually some white, easily-transported salts, then lower are some brown stains and at the lowest level is the distress to the brick or stone.
    3. One approach I use is to imagine the early stages of this distress. I could picture a ring around the parged and painted chimney where peeling begins and flakes off with pieces of brick. At that early stage there would be no doubt but that something (mortar, ash, rubble) filled to that level at the inside.
    4. Pretty unlikely that there is a concrete floor underneath this 1870s chimney. So while it may appear as though the chimney is perched on dry ground, it probably is wicking quite a bit of water up and out of the soil over the years.
    5. Basically, I don’t know [referring to the interesting shape]. Good one. Somebody keep a big dog in the basement who liked to scratch his side?

    So, seems as though we understand the degradation of the brick from rising damp but everyone is still pleasingly puzzled by the shape. Thanks all around, and Chris, sure seems as though you got your money's worth on this one!

  10. eugene sedita | | #10

    I have done brick repair for 40 yrs. I must have cut out a couple of square miles of brick joints over the years and come across many unusual and hard to solve problems. My business was not primarily building with brick but diagnosing and repairing brick homes and other buildings in the NYC. area. I tend to doubt the likelihood of moisture wicking up from the ground, if that were so I would think that other areas of the perimeter would also show similar damage. It's just too localized to have come up from the ground. Much more likely as one of your contributers suggested that the water came down from above. It is possible too that there was some kind of mechanical damage to the area caused by penetrations by holes and anchors to hold up some heavily used shelves eg. There also could have been some inconsistency in the building of the column which made it more likely to show damage at that height ( a poor mix) We have a joke here in NYC that Herman must have built that one. ie. an inexperienced helper, unsupervised made a bad mix or two or forgot how to count or misunderstood a direction which made this area deteriorate faster than either higher or lower. Of course one picture doesn't really give all the info I'd like to let me bet that I'm right but the odds and experience would lead me to those conclusions.

  11. Expert Member
    Michael Maines | | #11

    Chris, could you post a photo of the opposite side of the column, and show more of the top and bottom?

  12. Riversong | | #12

    What everyone seems to be missing is the remaining piece of cement parging just above the "waist", which has a struck (finished) lower edge. This indicates that there was a border of some kind at that level: either some fabrication surrounding the pier or that was the original finished cellar grade which was later dug out for a full basement.

    And if, as Chris states, this was not the chimney but merely a pier that was "part of the base of an old chimney ", then it's not likely to contain a flue or have deteriorated by water leaking from above.

  13. William Smigel | | #13


  14. Riversong | | #14

    You must be referring to that distant cousin of the carpenter ant: the masonry ant.

  15. Expert Member
    Michael Maines | | #15

    Robert, do you mean that spot of parging above a brick that doesn't match the others, and is about the size and shape of a chimney thimble?

  16. GBA Editor
    Martin Holladay | | #16

    An intriguing comment. Time for some forensic deconstruction and further investigation.

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