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What caused this chimney damage?


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I've never seen anything like this.

Here's a couple pics from a home built in 1994 with a site-built masonry fireplace. It was a two story with a 10 in 12 pitch so I didn't get up on it. The back side of the fireplace had a roughly "v" shaped, vertical cleft in it straight down the center from the band to the top of the cricket. The room it was in was a two story family room so there was no attic access. Since I couldn't get close on the roof, I couldn't get a good, up-close look. I am at a loss as to what happened. These are modern, hard-fired bricks so I can't see it being freeze damage. The pattern doesn't fit that scenario anyway. I can come up with two possibilities:

1. There was a chimney fire and the brick was forced outward from the inside, possibly due to inadequate masonry mass between the tiles and the exterior brick. It seems to me that pressure from the inside might explain the "V" shape damage to the brick.

2. A lightning strike. However, I saw no evidence of this otherwise.

Anyone ever see anything like this or have a better guess?

And now for something completely different...can someone with magical powers please change the incorrect spelling of received which you see after uploading a photo:The following file has been successfully recieved

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Three possibilities - one you've mentioned,

1) Before they put that metal cover on the crown of that stack the mortar cap cracked and allowed water to saturate those bricks directly under the crack and when the weather dropped to below freezing in winter the wet bricks spalled all over the place. The owner, seeing that, brought out a mason who said, "Lookie here, cracked cap, spalling brick, I need to put a cover on top of this thing to stop the bricks becoming saturated like this again.

2.) They intentionally knocked the edges off those bricks and built the stack that way as some kind of artsy fartsy detail.

3. That sucker got hit with lightning. Is it possible that back in the 90's they had a metal TV antenna pole secured to the chimney at that very spot and it became a lightning rod?

ONE TEAM - ONE FIGHT!!!

Mike

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Mike--

Your # 2 guess isn't it. Artsy-fartsy it ain't. You can barely see the chimney from way back in the rear, and not from the front at all. No one would have done it deliberately. Your # 1 guess, freeze damage, doesn't make sense to me either. I just can't reconcile the pattern of the damage. There's no overall surface spalling. Furthermore, the neighborhood that this is in requires full caps, even on masonry fireplaces. Given that, there would not have been much of a chance of any water entry and freeze damage. The sheet metal guys usually hustle and put the caps on using the mason's scaffolding anyway.

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Is there just one fireplace?

I have seen something like that before where a second chimney was added next to the original and they then tried to integrate both together.

Chris, Oregon

Single unit as originally built. No modifications whatsoever that I can see. The fireplace did seem pretty well used.

Jim--Those termites with a taste for fired clay must be a Yankee curse!

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Kevin,

I saw a chimney a few years ago that was nearly identical to yours and the damage had been created by lightning. I'm not sure I would have known that, but the buyer, when he called to schedule, told me the chimney had sustained lightning damage and the sellers were going to have it corrected as part of the sale agreement.

I remember looking at the chimney when I was on site and wondering why there wasn't any soot or other signs of charring. I later asked around and was told that the strikes were so intense there were seldom any signs one normally associates with fire and/or high-octane electricity.

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Thanks for the replies. My first thought was lightning, but the only lightning hit I have ever seen on a chimney did far more dramatic damage. It was about 20 years ago, on a house about half a block from my parents. The top of the chimney literally exploded, sending brick chunks up to 75' into the yard. The big sections landed on the deck. It also sent a lot of current through the home, blowing out the dishwasher, tv, and surely a lot of other things I don't remember. I do remember that it also caused the garage door opener to open the door. Shortly afterward, the owners arrived back from being out of town without a clue as to what happened.

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There are various degrees of lightning strikes. I heard my old rock mason let out a horrifying scream as he was jingled with lightning via a metal chimney. He was working wet mortar and rock around the fireplace opening/hearth area. The same storm produced a lightning strike that split the trunk on a 30â€

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  • 6 months later...

I have seen many lightning damages, and this is not it. For electrical shock to split a chimney without blasting bits of masonry all over the place is unusual. Further, the metal cap is still in place and intact, holding the top bricks in place, are we going to say the lightning was selective in which bricks to damage? Lightning follows paths of least resistance, which is why you may see a trench of soil created by a lightning blast that hits a satellite and follows the cable.

This appears to be related to something internal, such as a piece of corroding steel, expanding and forcing the chimney apart. Did you ever get a look inside of the masonry?

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