Staggered Cinder Blocks with Open Holes

[ADDvanced]

Hi, I am a new home owner. I had the chimney's inspected today, and didn't get good news. I'm used to chimney's being lined with that reddish/orange plate, but mine it just cinder blocks. Additionally, the flues sort of connect into one large flue, and the blocks are stacked like legos. When I put my head in the fireplace and look up, I can see holes on the bottom of some of the overhanging cinderblocks.

It looks like the fireplace was used often, and the house is still here, but the chimney inspection guys said I need to cut out the flue and they need to rebuild it all with mortar. Thing is the bottom of these bricks look like they never had mortar to begin with.

Help?

 

[jatoxico]

What does the chimney serve (oil burner/stove/fireplace) and what are the dimensions? Example oil burner in basement, fireplace on first floor etc. And how large is the final single flue?

 

[webby3650]

It sounds like you are looking at the smoke chamber.(a little room directly above the damper)? Then the flue starts at the top of that, typically 3-4' up. Does the flue its self have clay lining?

 

[ADDvanced]

Yes, I guess it is the smoke chamber. The flue has ceramic lining, but the smoke chamber is just cinder block. Do I HAVE to seal the underside with mortar? I didn't see any cracks.

 

[bholler]

Yes, I guess it is the smoke chamber. The flue has ceramic lining, but the smoke chamber is just cinder block. Do I HAVE to seal the underside with mortar? I didn't see any cracks.

If there are open cores exposed the nyes they all need sealed. If we were dong it we would cover the smoke chamber with wire mesh then apply layers of cement designed for smoke chambers. There are types that spray on and types that are troweled on.

 

[heavy hammer]

The smoke chamber is supposed to have a smooth mortar finish. As bholler said it needs done, I was a brick layer for over 12 years when a smoke chamber is built the inside is done with brick and block an on the way up is plastered/made smooth with mortar. It is supposed to give the smoke a place to roll if need be instead of coming back into your house, and made smooth so there is nothing for it to stick to or collect on. It's not a hard fix just time consuming and probably a dirt job if the chimney has been used.

 

[bholler]

It is supposed to give the smoke a place to roll if need be instead of coming back into your house,

No it is supposed to smoothly transition from the firebox to the flue with as little turbulence as possibly rolling is a bad thing. Otherwise you are right on. But many masons never parge the smoke chamber. Most do not allow open block cores exposed though.

 

[jatoxico]

What about the multiple flues converging into one? What are flues doing?

 

[heavy hammer]

The rolling is not what you want, I do agree but if you have turbulence you don't want it coming back into your home. The guy that taught me to lay brick and block always told me this when doing fireplaces. You just want a nice smooth transition from fire to outside your house. I have never not seen a smoke chamber not plastered/ parged. But I have seen many other questional builds. Anyways bholler is right it needs addressed.

 

[bholler]

I do agree but if you have turbulence you don't want it coming back into your home.

Yes I have heard that many times as well but the physics does not back it up at all.

You just want a nice smooth transition from fire to outside your house.

Absolutly correct

I have never not seen a smoke chamber not plastered/ parged

I would say that only 1 in 10 that we look at are parged.

 

[heavy hammer]

Maybe the smoke rolling is just an old timer thing since the guy that taught me learned how to lay from an old Finnish bricky. The smoke chambers left unparged is interesting. But every bricklayer I'm sure is different, it doesn't make it right.

 

[bholler]

it doesn't make it right.

No it absolutely is not right I am not saying that at all. It does not meet current code either but we still see it on new build all the time.

In most cases it is just a performance issue but in this case with open block core it could be a very serious safety issue as well.

 

[heavy hammer]

Absolutely that is a perfect place for a chimney fire. There is very little inspection when a masonry chimney is being constructed, at least here in Ohio. Most inspectors don't even know what to look for when one is being built. At least you should stay busy for many years, it's just a shame to see this on new construction.

 

[Corey]

I guess to me, it would depend on what you intend to do with the existing flue. If you're going to burn an open fireplace, then I'd defer to what ever expert analysis you choose from above. If you're going to line it and use a wood / gas stove or insert, then according to the 'rules' the masonry doesn't really count anyway, so I likely wound not spend a lot of time chipping, patching, etc if you're going to put an insulated liner in anyway.

 

[webby3650]

We rarely see a smoke chamber that's parged, I'd also say 1 in 10. I have taken a product called ChamberTech and actually made balls out of it and thrown it at the smoke chamber. You can use this method to fill voids, or fill in around a new liner in certain instances. After it's stuck you can use a wet broom to smooth it out. I don't think this method would work to parge an entire smoke chamber, but you could at least fill the holes in the block. http://www.chambertech2000.com/facts.html

 

[bholler]

I don't think this method would work to parge an entire smoke chamber,

yeah it does that was what it was designed for we do quite a few

 

[Destructor]

When I worked with my brother building chimneys we always used solid block or solid brick in smoke chambers and parged them. Open cores, especially large concrete block cores potentially could expose framing to heat and smoke. Concrete block doesn't corbel very well anyway for use in a smoke chamber. Usually block is only used on the vertical walls of the chamber.

 

[ADDvanced]

Well this house was built in 58.... and it looks like it's been used for about .. oh... 58 years or so without issue. I guess what I'm getting at is, I realize it isn't to code, but if it has been used in the past without issue, I'm struggling to see the point of 'fixing' it.

 

[Squisher]

Google 'wood pyrolizing' and you will find out why houses that have 'burnt this way for fifty years' can one day burn down.

The old it's been fine this way forever argument. Does not hold water with wood burning systems.

 

[Lake Girl]

Well this house was built in 58.... and it looks like it's been used for about .. oh... 58 years or so without issue. I guess what I'm getting at is, I realize it isn't to code, but if it has been used in the past without issue, I'm struggling to see the point of 'fixing' it.

Sorry you don't like the answer you are getting.. I would err on the side of caution as lives cannot be replaced and property damage claims could be ignored by insurance since you have an identified problem. bholler's regular day job is a licensed chimney sweep so he knows a little bit about what he speaks. How much of a repair may depend on what your intentions are and how many other fireplaces/appliances are utilizing the chimney.

 

[kennyp2339]

So if the repair is costly why not install an insert with an insulated liner and call it a day, plus the efficiency of an insert trumps and open fire place 10 fold with cleaner burns, better drafts, and most importantly great heat.

 

[Lake Girl]

So if the repair is costly why not install an insert with an insulated liner and call it a day, plus the efficiency of an insert trumps and open fire place 10 fold with cleaner burns, better drafts, and most importantly great heat.

Sounds like a shared flue so that needs to be corrected too...

 

[ADDvanced]

So yeah, I think an insert would be a good idea. However, my GF says that inserts are not safe to leave burning over night. Is this true? I know lots of people who burn over night without issues, but is there any literature that says that overnight burns are okay?

Thanks!

 

[bholler]

So yeah, I think an insert would be a good idea. However, my GF says that inserts are not safe to leave burning over night. Is this true? I know lots of people who burn over night without issues, but is there any literature that says that overnight burns are okay?

Thanks!

Totally untrue if installed correctly with an insulated liner they are very safe

 

[begreen]

Sometimes ZC fireplaces are called inserts. Maybe that is where she heard this? There are some zero clearance fireplaces that are not designed for 24/7 heating, but I can't recall a fireplace insert that says that.