exterior brick chimney rebuild

[KarlP]

Our stove is installed through a 6" clay lined thimble about 6.5' up a 32' exterior chimney with 8x8 clay liner. We got a lot of water on the hearth during Irene but there was no water on the wall or in the stove. This hasn't happened before so I thought it was sort of weird.

We're having the roof done this week and the roofers indicated there was a 1.5" gap between the roof and the chimney. So I take a closer look at the chimney. About 6' up there is a 3/16" gap on both sides of the chimney at the house. I'm guessing the faster heating cycles at the thimble weakened the mortar there so it was the point of failure.

The gap tapers to nothing about 3" from the face of the chimney, however there is a crack on the face from side to side in the mortar joint above that. The chimney clearly begins leaning away from the house after that.





I have my mason (in his late 60s, decided to semi-retire and sold his equipment for big jobs in May , but a partner he worked with for six years still has his equipment and they sometimes work together on bigger jobs ) coming to take a look at it tomorrow morning.



There are only three things I don't like about the chimney.

1) The cleanout door is 4" above the ground. It is a pain in the butt to get the rods up and debris out in normal conditions. Even worse when I don't spin-trim for a while or there is 2' of snow on the ground.

2) Two minor issues because it is a long clay lined exterior chimney with about 11' above the roofline. I average about a little over a gallon of soot and creosote for every cord I burn, but it comes off easily. I get downdrafts in spring and fall when we have cold nights and it warms up quickly in the morning, but once I reverse the draft it drafts VERY well ... have to watch stove carefully when temps are below 10F.

3) The thing is probably going to fall over, and I don't feel safe using the clay liner for much structural integrity when burning ... and I suspect it is right now.



I am going to ask his opinion about repairs, but I'm guessing a total rebuild is required. In that case I plan to ask about rebuilding with a 12x12 clay liner and a cleanout door about 4' off the ground instead of 4". That way I will have a chimney with a wider stance which I hope is stronger. I can run the stove up an insulated flex liner inside the clay liner, install a T at the thimble, and reach the bottom of the T with my arm in the cleanout door. With the insulation on the flex liner and then a clay liner the chimney shouldn't expand right where the thimble comes through and weaken the mortar there ... so a hurricane won't break things loose.

With the insulation on the flex liner the chimney shouldn't expand right where the thimble comes through and weaken the mortar there so a hurricane can knock it loose. If I want to reconfigure I can switch out the liner with something else without having to rebuild the chimney again. Super safe double lining system. Easy to change in the future if I want to switch to an 8" liner, coal stove, etc. If sealed from the weather, clay tiles will outlast my kids. Flex liner is easy DIY.


If the footing for the chimney is exactly the size of the current chimney with 8x8 flue... would you rebuild with 8x8 clay and hope it doesn't happen again? 8" round stainless liner? 6" round stainless liner? Class A chimney inside a brick chase? Pour a new footing so I get the wider chimney stance & 12" flue options?



Uugh. Paying a ton for a roof & trim right now. We are leaving in a week for our first big vacation in two years. Work is suddenly busy so I don't have time to take this one down. Weather will start getting iffy for chimney rebuild when I get back two weeks later. Uugh. On the bright side I have a working 1 year old insert and working 40 year old gas furnace in the chimney this guy rebuilt from the roof up 6 years ago.

 

[begreen]

Other options to consider:

A) Install a class A insulated chimney system instead and chase it if desired. This will cost less, and function better.

B) Install a new flue system straight up in the interior of the house (even less expensive and better functioning).

 

[webbie]

It is pretty normal for chimneys to pull away from the house....we ran into it a lot back in NJ. The foundations for the chimney settle differently than the house.

There are probably various options......short of 100% rebuild....

1. Line it with good heavy rigid ss if possible. Then use a couple iron bands, perhaps one every 10 feet, to strap it to the house. Strap into the bands (end joists) with heavy lag bolts - perhaps into the attic with through bolts if possible.

2. Same as #2, but bust out flue tiles and, if enough room, pour a Ahrens or similar poured liner systems - which buttresses the entire chimney. Band to the house - and also possibly wire and stucco the chimney exterior.

You can also buttress the foundation. This can be done in various ways...such as digging down around it and pouring a shitload of concrete in. You can even dig out under it, while bracing up the chimney, and do this. My installer was an expert at this - he used railroad jacks and actually put the chimney back tight against the house! He would then pour concrete around the jacks.....embedding them!

 

[webbie]

Note - here is an example of a chimney banded to a house...

 

[KarlP]

I was thinking it was the foundation and going call a foundation repair person to put in a steel pier and push it back against the house until I realized the footing is perfectly square to the house and looked more closely. The lean doesn't start till the cracks six feet up. Below that is perfectly vertical.

Everything I've read said banding will eventually pull the house over to meet the chimney which is not the direction I'd like to go. Have to see what my mason says about repair possibilities. He's one of two contractors I've ever found that I completely trust.

If I go interior chimney I'm running chimney pipe through the smallest bedroom shrinking it further. Want to stick with exterior. and a brick chase goes with the character of the house more than anything else.

 

[webbie]

In most cases, I really doubt that a normal chimney would pull on the house. The force which with a vertical chimney leans slightly is relatively low. But you are correct that each instance has to be looked at on it's own.
Just be aware that many chimneys are banded to the house - and I have seen many also bolted to roofs with braces. None seemed to have pulled the roof out.....rather the chimneys stayed straight.

 

[elmoleaf]

Not really sure what/where these gaps are located. Building codes require airspace between masonry chimmneys and combustible framing.
Chimmneys are supposed to be self-supporting. It's not uncommon for older (100+ years) chimmney's to develop a lean above the roofline. Typically those can be torn down to the roof and rebuilt.

 

[KarlP]

The 3/16" gap is in the horizontal mortar joints on the back of both sides of the chimney. At the front of the chimney there is no gap, but the row in the bricks above the horizontal crack is 1/16" closer to the house than the rows below it. There is no mortar joint holding the chimney together 6' up. Its just gravity and the clay liner.

 

[tfdchief]

It is pretty normal for chimneys to pull away from the house....we ran into it a lot back in NJ. The foundations for the chimney settle differently than the house.

There are probably various options......short of 100% rebuild....

1. Line it with good heavy rigid ss if possible. Then use a couple iron bands, perhaps one every 10 feet, to strap it to the house. Strap into the bands (end joists) with heavy lag bolts - perhaps into the attic with through bolts if possible.

2. Same as #2, but bust out flue tiles and, if enough room, pour a Ahrens or similar poured liner systems - which buttresses the entire chimney. Band to the house - and also possibly wire and stucco the chimney exterior.

You can also buttress the foundation. This can be done in various ways...such as digging down around it and pouring a shitload of concrete in. You can even dig out under it, while bracing up the chimney, and do this. My installer was an expert at this - he used railroad jacks and actually put the chimney back tight against the house! He would then pour concrete around the jacks.....embedding them!

When I was part owner of a Construction Company, (before I became a no it all inspector lol) we used to do this all the time. It really caught my eye when you posted Craig, because I have never heard of anyone else doing that. Funny story......on one job one day, the concrete truck driver ask as we ask for concrete down the shute......"Aren't you going to take those jacks out?" LOL. "NO THE DAMN THING WOULD FALL DOWN IF WE DID THAT!"

 

[KarlP]

My mason stopped by and gave me 15 minutes of free advice. He's seen ones leaning 8" away from the house that were really hard to pull down. He wouldn't worry about it pulling away only 1.5". The chimney footing seems level/square/solid. If he were to rebuild the chimney he would have to rip that one out, put bolts through the basement wall and pour a new one to meet today's code.


He suggested I talk to someone in a metal fab shop about making a heavy 4" wide band to go 3/4ths the way around the chimney with tabs on it. I can put that around the chimney and bolt it through the outer (double) floor joist in the attic to prevent the wind from doing any more damage. He said the house probably isn't strong enough to pull the chimney back up or hold the it up if the lean were caused by the footing sinking on one side, but its plenty strong enough to keep it from leaning any further in wind gusts if I put a band half way between the crack and the top.

So he suggested -
- stick a camera through the thimble and shoot a couple pictures to make sure clay liner not cracked at the masonry crack ... it is probably fine.
- add a band around the chimney bolted through the attic floor joists
- cut the siding back a few inches from the chimney and add some thick trim & caulk to prevent water leaks
- fill the cracks in the mortar with clear caulk so ice doesn't do any more damage to the joint
- reinspect the mortar crack after every big storm

It may continue to move and need to be rebuilt from the footing up... or it may not move any further in my lifetime. He wouldn't worry about it unless the lean doubles.

Phew!