3/4" separation between chimney & house OK?

I just inspected a house that had a fireplace added in the basement about 25-30 years ago. The chimney has about a 3/4" (2cm) separation from the house. It was not visibly leaning, but there was some cracking noted on one side of the fire brick inside the fireplace.

According to the sellers, it was built as a “free-standing” chimney, not supported by the exterior wall. Obviously it was attached to the foundation at the fireplace itself.

Is this sort of gap between the chimney and the wall normal for such a structure or are the sellers “blowing smoke”?






I’m no expert on chimneys, but I can certainly see a problem with moisture freezing/expanding in the 3/4" gap, particularly on the front side where rain and snow can go straight down behind the chimney.

Jim King

I can only imagine that it will get worse, I would defer it to a professional mason.

Appears to me that there might be some structural concerns here as to why it is pulling away from the house.
It definitely needs further evaluations.

Marcel :slight_smile:

It appears that the chimney was not properly anchored to the house when it was constructed. Potentially very dangerous. I have inspected the aftermath of a chimney collapse due to the lack of proper anchoring.


The gap appears to be consistantly spaced.Not wider at the top than at the bottom.If the gap at the top was wider I might be concerned that the chimney is leaning or pulling away.
Another thing that makes me think it is not moving and is free standing is the area at the soffit and facia.I see no gap there,only a messy paint job.
What did the flashing and shingles look like in that area.
A good poly type caulk would stop any water , wind, and insect intrusion.
That being said , there is absolutely nothing wrong with consulting a fireplace mason for an opinion especially if it helps you sleep better.


Just wanted to point out that this fireplace chimney was installed after the fact and the foundation and anchoring to the Home is inadequate. Obviously from it’s separation, further evaluation is required.

Marcel :slight_smile: :slight_smile:

Thanks, everyone.

The fireplace and chimney were obviously designed that way, though it’s apparent from the mortar on the inner edge there was not originally such a gap. I had originally suggested the agent check for permits to see that the construction was deemed up to code by the city and see just how long ago it was installed.

A Cheremie points out, the gap does appear to be consistently spaced, and I did not see evidence of significant recent movement, judging from the fascia caulk. If the gap were noticeably wider at the top than at the bottom and/or a noticeable separation of the caulk and the aluminum fascia wrap were evident I would be much more concerned.

My main concern is whether or not the chimney is likely to sink relative to the house, which would cause it to twist out, being attached to the foundation at the fireplace. However, the bottom of the fireplace is more than 42" below grade, which is considered an adequate footing here in Michigan, so I think the soil beneath the chimney is well compacted by now, and it’s highly unlikely there will be any more significant movement of the chimney in the near future.

No matter how you look at it, I would still call it out for further evaluation because that gap is a perfect spot for moisture/insects. To me, that gap should be sealed no matter what IMHO.

absolutely call it out. CYA!

It might be fine if the chimney-supporting foundation is good, but consider how many situations we see every day that result from poor soil compaction. It seems to me that soil compaction beneath this type of structure is critical and tying the chimney to the home near the roof would be a prudent measure.

What is the advantage of a having a heavy chimney like this not tied to the home?

The fact of the matter is none of us knows wether it is tied in or not.
The block behind the brick veneer could very well be tied in. We just don’t know. We werent present when it was built.
As far as soil compaction goes , if the footing was put on undisturbed soil there should be very little , if any , compaction. If the over-dig was so great in that area that fill dirt was required and then that should have been engineered .When something is engineered there is always stamped documentation. But after 20 or 30 years that document is probably long gone.
The brick and mortar joints on the chimney and house line up horizontally which tells us the chimeny is not sinking.The gap is a consistent width from top to bottom with no ill effects at the overhang which tells us it is also not leaning.
I would definately recommend a good quality caulk for obvious reasons and because if one tried to re-tuck point it the mortar would likely not stay bonded.
Personally I think it looks quite good for something that has been there for 20 or 30 years. But its just my opinion , I have no need to be right but if you add all these fine folk’s opinions up ,the machine just might work!


or . . . it could be the house that moved, not the chimney! regardless, it should be inspected by an engineer, not a mason.