Learning More About Chimneys

It’s in the low 90’s this week and I can’t believe I’m dreaming of cold fall days. I’m hoping this fall we can get at least one of fireplaces functioning. Winter will be here before we know it!

I had someone over this morning to take a look. I was told my chimneys are too large for metal liners. So now what? It seems like I have two options. Option one, we could have Smoktite installed in the lower smoke chamber of our chimney. Smoktite is a ceramic product, “that is sprayed in smoke chambers to seal holes and gaps.” I could then have a camera dropped to look for any holes. If they find holes I could get them patched.

Now option two, Thermocrete. It looks like this stuff is made by the same guys that produce Smoktite. “Thermocrete process coats the inside of the chimney from top to bottom with a highly durable ceramic sealant.”

I’ll have to do some more investigating and find out cost-comparison and pros and cons to each. I do hear rumors that Thermocrete can cost you around 3K per chimney. But then on the same website I found info for CFS and Dynacote, which sound like other sealant options. What the heck is the difference between all of them? If you have any experience or tips for old chimneys please share. I’m a total newbie!

Related Posts:
Day 3: Brick Chimney Build
Day 2: Removing Brick From Old Chimney
Day 1: Chimney Rebuild

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  1. Don’t get discouraged. Your new chimney looks awesome, take pride in that, as it was money well spent on something you guys couldn’t do. The interior is coming alone nicely as well and that is all your work :-)

    The roof will have to be done now because the masons did a job on it. The Suposed rotted wall and claps can wait. Contractors love to play up the rot so don’t let that bother you at this point. Get lots of quotes on your roof. Whoever does it will be in and out in one day, two at most. Roofing is a very lucrative business. If the estimate you got is from someone with a lot of work lined up, they most likely bid it high. They don’t need the work but if you bite, they’ll fit you you in. Measure the square feet you’ll need and compare your pricing here…


    Clap boards are easy to replace. Just set the nails with a straight punch all the way through on the problem clap, and the one above it. You can then slip it out and slide in a new one. Fill the nail holes with glazing putty. Use pre-primed claps. To tell if you have any rot, try to push a putty knife into a clapboard along the grain. If it goes right in you have rot, if not, your good.

    The green staining in the back where the mason’s staging was set up is because there is really no roof overhang for the water to drip clear. If you sprayed clorox outdoor bleach all over your siding…


    Your house would sparkle! Hand sprayers are a lot of work but a pressure washer has a siphon hose that would blow out a whole gallon in 5mins. Paint is just as washable as vinyl. No scrubbing is required, blow it on and wait a full 10mins and anything green and black will just disappear. Then rinse.

    Keep your head up, many folks are rooting for you!


  2. Thanks everyone for all your comments. I totally understand the heat loss of having a fireplace and the advantages of switching to a stove. We currently have 4 flues. Two on the first floor, two on the second.

    The two on the first floor will be in a kitchen–non-functioning, second in a family room–hopefully putting wood stove here.
    The second floor was the only place I wanted to keep real fireplaces. The mantels and rooms are the most historically accurate and even if I only use them occasionally I want the option.

    But all of this may have to take the back burner for now. We just a new quote for a new roof, a rotted wall and sill, and rotten clapboards. Ug. We’ll see. Today I’m feeling overwhelmed…


  3. Also, not sure if you did this already, but before you decide which fireplaces to make “working” you should confirm very firmly that you have separate flues all the way up to the top for each of them. One of ours was put out of commission by our furnace exhaust pipe.

    good luck!


  4. I faced similar decisions three years ago in our 180 year-old chimney. At the time, I felt like ‘well it has been operating fine for 180 years so what is the big deal?’ But after having to remove some of the siding on that side of the house (for unrelated reasons) and seeing the real condition of the chimney parts that had not been repointed and rebuilt, I changed my mind.

    All the pros we had out wanted to do a similar kind of blow/pour-in reinforcement, but we didn’t like that it wasn’t reversible and wasn’t guaranteed to last that long. Once you cement in in, it is there forever and you’d have to nearly knock the entire chimney down if you ever wanted to enlarge the flue(s) again. (unlikely, right, but in the LONG long run multiple layers of stucco required for repairs, etc will add up. You will be putting that problem off onto future generations of owners.)

    I agree with Amy D’s post, it seems wrong that they said it would be too large for a metal liner. We had one put in ours and they insulated the remaining space around the liner to help the draw. I assume they meant the firebox was too large (I think the flue diameter is linked to the firebox volume). FYI your fireboxes themselves, though really beautiful, are going to be a problem for any reputable chimney company because the distance to combustibles (the wood surround) is probably not to code by current standards. They will want you to add masonry to the box to make it smaller and the distance to combustibles larger. This would be a real shame from a historic perspective, and again there is the reversibility issue.

    Anyway, for what it is worth, in the end, we chose to install a wood-burning insert with the largest glass window we could find and ran a metal round liner up the chimney in the firebox in our main living space. Vermont castings makes nicer-looking ones that are almost flush to the wall. My husband almost left he was so against closing in the open flame. But I can tell you that after the first winter he came around pretty quickly. Since it is safely enclosed, and cleaner/slower burning it is easy to keep the fire burning most of the time (not just special occasions and evenings when you aren’t too tired to build a fire). You can fall asleep in front of it, leave the house, etc and it has cut our heating bill by nearly half. With long winters, I can’t tell you how nice it is to have a constant fire and not worry about it–especially if you work from home.

    Sorry this is so long. I very much enjoy your blog. Please email if you’d like to hear more (ha ha).

    all the best…


  5. Great blog! And your house is definitely an historic gem. Old houses need people like yourself to look after and care for them: and your doing a wonderful job. Just think of all the prior lives that were lived out in your house in the past, and now you get to enjoy it!

    Certainly the best feature of your house is the central fireplace with its raised paneled breast. http://i54.tinypic.com/24q5s2c.jpg

    And since this thread is about chimneys one thing to consider is heat loss though your multiple flue chimney in the winter months. I lived in a 1745 house in Westport Ma that had an identical central chimney as yours and it had no dampers! In the 1700’s they weren’t thinking about drafts

    Warm air inside a house rises up the always open chimney pulling in outside air (which could easily be 10 degrees on a cold winters day) from every nook and cranny in an old house. You don’t need a fire for this to happen. When you do have a fire though many cubic feet of air rises up the chimney in a single minute. Every one of those cubic feet of air needs to be replaced, and they come the outside. This happens because the air pressure in the house cannot not and will not be lower than the air pressure outside.

    Even furnaces and hot water heaters flued through a chimney do the same thing, suck in cold outside air from where ever it can. Today’s 95% efficient heaters eliminate the need for the chimney!


    When people heated by fireplaces the only warm place was directly in front of the fire. The rest of the house froze from all the cold air outside being sucked in. I guess that’s why that had those high back benches, to keep their backsides warm.

    Another thing I noticed was the road noise. With all the windows shut I could hear the road traffic as if I was standing outside. To my surprise, after stuffing thick insulation batts in the flues all was quiet. So chimneys in old houses are like wide open windows that no one ever sees.

    Is there a roof access in the attic right next to your chimney? Chimney fires were common way back when and they use to use this convenient access to pour sand down the chimney to smother the flames. Cold water on hot brick (or a clay liner) will cause it to fracture, ruining the chimney.


    Have you considered having the masons put a capping stone (bluestone) to prevent heavy rains from running down the flues. These rains have the effect of washing out the soft limestone mortar.

    Personally I’d treat your central chimney as the artifact that it is and not try and make it functional. To install a damper in the smoke box you will have to remove the paneled wall in front of the chimney and take many bricks out of the chimney to install it.

    Slow and steady wins the race. Lots of research will pay off in he end. Keep up the good work!


  6. I know you want to restore your house in the most authentic way, but have you looked into converting at least one of the fireplaces? Open fireplaces, generally, are negative sources of heat (they draw warm air out of the room and put it out through the chimney.) So relative to the fuel that they consume they make your room colder, not warmer. Installing a wood stove insert is going to make your rooms warm and give you great fuel efficiency. There a some options that you can retrofit into an existing fireplace.


  7. We are renovating a house too and my husband is skeptical about the comment that your chimney is too large for a metal liner. A chimney can be too small but not too large for a liner. Get a second opinion:) The house is coming along, keep up the good work!


  8. We had someone come out with a camera to look at ours. We have a ceramic liner, but it’s about 80 years old. They said we could either pay to have them patch the cracks in the existing ceramic liner, or get a direct vent fireplace (I think this is only for natural gas though). The direct vent deal appealed to me since it’s suppose to actually heat your room and many are rated as or more efficient than a furnace. You can use your current chimney/firebox depending on your chimney’s height. If you google direct vent you can see photos. Obviously direct vent won’t look as authentic to the period of the house though which concerned me. Both options ran around 4k though – so we replaced our sunroom windows instead!


  9. fascinating!! I’ll ask my father in law who built a camp, and seems to know everything about homebuilding, if he has any insight on this. I had no idea a chimney could be so complicated!


  10. I’d be cautious about lighting a fire before getting it checked out/fixed. My aunt had a chimney fire at her house during thanksgiving. The fire had been burning all day and we had all gone to bed. We were woken up to smoke alarms the house filling up with smoke. The fire dept came and had to cut through the walls of each floor of their house (they had a finished basement and a second floor) to locate the source of the fire. The fire happened to be behind the wall in their bedroom closet. Needless to say there was a lot of damage, not only from the fire but from the smoke (which was probably worse). I’m not trying to scare you but rather saying be careful!


  11. I’m with Liz– definetely have the local fire department come over and give you their opinion. They are the pros and have an unbiased view because they’re not trying to sell you anything! It is soo important to do this job right! Good luck! :)


  12. I hear many people get ceramic liners. Re lighting a fire without one — you at least need to get the chimney inspected by a chimney sweep first. You’d be crazy to light a fire before doing that. Because indeed the house COULD burn down. I don’t know about those guarantees though. Shouldn’t they guarantee their work if they put in a liner?


  13. From my understanding the chimney liner is really a necessity…. That it is a safety precaution so that if the bricks become loose and clog the chimney you don’t make your house a gas chamber when you light a fire. But, regular cleanings and chimney maintenance can serve as a substitute. You just have to be sure to check it at least once a year.


  14. We have a ceramic liner, installed on the advice of our local chimney sweep, after a chimney fire 2 years ago. I think it might be thermocrete.


  15. i hope this doesn’t sound too obvious so please forgive me if it does – how about asking the local fire dept to check it out? they should be able to point you in the right direction and I’m kinda w/G on this one – there are a lot of products out there being sold purely to make money…they don’t neccessarily make anything better.
    good luck!


  16. I’m not convinced we need any of this at all. I’ll light a fire this week and if we don’t smell smoke and the house doesn’t burn down – we’re good!
    These companies and products are not going to make any 100% guarantees and won’t be liable if the house burns down.