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Question DetailsAsked on 7/21/2015

Exterior block degrading on a poured-in place chimney liner.

Previous owner of 18 yrs did no maintenance, but claims poured-in place last a lifetime & hold exterior together. Chimney inspector refused to clean chimney, claimed due to exterior block cracking that the poured-in liner would not be good. Then proceeded to try to sell me a new installation of stainless steel pipe elsewhere in the building--liner is 6" ID & no room to install any other liner inside. Searching internet gives no info on what type of regular maintenance, how to tell when a poured-in place liner is going bad. Exterior block appears to be 6" high hollow squares 12-16". Tearing down the chimney to roofline would cost about $800, & would still leave me w/an unusable chimney stub in the middle of the basement.
Anyone have any experience of any kind with this type liner?

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2 Answers

Voted Best Answer

Don't buy it - interior poured-in-place liner is not designed to hold the exterior together and is not structural - is a flue liner only - if the exterior blocks are deteriorating they need to be replaced or the chimney torn down, because they are what hold the chimney up. Chimney Sweep was right and he or chimney Mason is the type of expert you should be listening to on this, not the previous owner.

6" ID liner - sounds like this is a furnace/water heater flue, not a fireplace - or maybe a gas or wood stove insert ? Certainly not a wood burning fireplace at that dimension - at leazt not legally.

You tell the liner is going bad by inspection - drop light and/or fiber optic camera inspection for one that small, crawling down in or camera for large flues - after thorough cleaning, of course.

You said exterior block is hollow - should have had at least (number of cells that have to be filled depends on local code and seismic / wind zone) one cell in each block filled with small-aggregate concrete or grout with rebar - perhaps the lack of reinforcing and grout filling is the reason the block is falling apart.

Answered 5 years ago by LCD


Thank you for your answer, LCD. The chimney was meant for a wood stove only, not for fireplace. I don't really know how the cells of the chimney block were filled, I only meant to describe that they weren't short bricks laid up, but full block with flu inside.

The owner did get his own 2nd opinion, & was told similar report of bad condition. I know that company doesn't have capability of doing a video, but they did convince him that not having a chimney cap over the opening for extended number of years would degrade mean rainwater would degrade any cement liner. He's agreed to reduce sale price to cover my expense of replacing the chimney.

I also found the 800# for a company that does poured liners & they were nice enough to answer my questions even tho I don't know what brand this one is. They did inform me that a chimney cap is required, they recommend annual cleaning & inspection, & that inspection must ensure that the crown has not cracked (which would allow water to get down between exterior blocks.

I'm looking forward to having safe wood heat with a new stainless steel insulated chimney.

Answered 5 years ago by Guest_99326201


Glad you got some good advice that gives you a comfortable feeling about this, and a price adjustment on the house.

Personally, I do not trust poured-in-place liners - because after thay cure they are already micro-cracked, which tends to open up with time - just not safe to me. I would go with a double-wall stainless liner every time. Whether a properly sized one for the wood stove will fit into the existing liner with required clearance may be an issue. Plus you have not solved the deteriorating block issue yet - you will need a Mason experienced in chimneys for that probably - or have the damaged part of the chimney demolished (commonly done to roof level) and just a stickup metal duct above the roofline.

Answered 5 years ago by LCD

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