repairing a neglected chimney, flue, thimble, liner, and leaks

BigMak · June 2

the setup: 1940's era built home, several addon. originally, an external chimney, cinderblock with clay liner. original boiler, (my post;

https://forum.heatinghelp.com/discussion/180778/american-radiator-company-ideal-no-7-boiler

since its inception, a garage and then an apartment conversion has enclosed the chimney. prior to my renovation, there where some patch work repairs done to the chimney to address the leaks. but the boiler's vent pipe, and a water heater exhaust was fed into the chimney chamber opening, (never connected via a thimble to clay flue liner), which was half basement cinderblock wall & have cinderblock chimney. the chimney was never properly sealed to the basement wall. a 1.5 inch gap was left, because it was built directly on to the cedar siding. this has allow some exhaust to escape leaving soot behind as evidence.

Today I've started renovations to the apartment and I am able to see the full extent of the deterioration to the chimney. hole and crumbling cinder block. I removed all the loose material and ready to repair.

I will probably put in a 6" S.S. smooth liner with a 27 inch snoot and seal against the basement wall with a thimble. but first i need to seal up 3 side, support the 4" cinder block wall cap, and fill the 1.5" gap above. for the caps, I was going to insert a metal bar, 22" x 3" x 1/4" to act as a header. and the sides i was thinking fire brick or cut cinder block to size and fill with high temp mortar. as for the top gap, 2 ideas; 1) sandwich 2ea .5 cement board, with mortar in between each and on the outsides hoping it will stick. or 2) lath with H.T. mortar and a form till it sets. I've tried cleaning as much soot from this area as possible with water and a wire brush. might even apply a bonding compound as well. hopefully this will seal it from any exhaust leaks.

Additionally, at the top of my chimney, the liner extends an additional 16" exposed. I don't believe this is compliant. I will probably have to extend the surround up, or trim it down for structural

safety.

I'm looking for additional suggestions on this project especially with the top gap. I'll include pics for reference.

as for the boiler, it has a 9" exhaust, if i go to a 6" S.S. liner, I will be restricting the air flow by 50%, as opposed to the clay liner which is 8.5 x 8.5, with an interior 7" x 7". but i don't have much of a choice as the clay liner termination is in poor shape. Ultimately i should replace the boiler to match exhausts.

thoughts? thanks in advance.

mattmia2 · June 2

You need a chimney expert to inspect all of that. It is coming apart because water is leaking in through that failed masonry that someone tried to glue together by parging it. I suspect at very least it needs to be rebuilt from the roof line.

Jamie Hall · June 2

Unless you happen to be a good mason and chimney guy, chimneys really aren't a do it yourself project. Take @mattmia2 's advice.

Oh — and every single picture up there is of a dangerous mess…

EdTheHeaterMan · June 2

Or you could remove the masonry chimney completely and use the void left behind to install a manufactured chimney like this: https://www.selkirkcorp.com/en/product/supervent/ . This is a DIY type of project.

Making a masonry chimney work properly without the water problems you have, is a job for the experienced Professional.

If you get the liner in there and there are any nooks or crannies for water to accumulate, then that water freezes and expands the bricks or stones apart, all the work you have done will be a mess in just a few years. Do it right, or don't do it at all.

BigMak · June 2

Ed. I have considered that option too, a new stack. I even looked into a faux chimney facade to maintain the traditional look. many advantages to new stack, especially considering the condition this is in, and just like everything in this house has been neglected by previous owners. Agreed, do it right or don't do it at all.

EdTheHeaterMan · June 2

How old is your roof? If it is more than 20 years, perhaps you can plan on replacing the roof in the next year or so after your new manufactured chimney is in place. Nothing like a professional roofer completing a new roof after you make a change to one of the holes in the roof. You may also qualify for some government assistance when you get your new roof. My state offers grants that can cover up to one half the cost of a new roof. Professional roofers will know about those rebates/grants.

Bob Harper · June 4

So you have a CMU block chimney that was improperly built on day one, improperly modified, had two combustion appliances improperly connected, improperly maintained, improperly repaired and you want to stick a Band-Aid on it? Sorry to break the news but this is waaaay beyond resuscitation. An interior chimney must be built to NFPA 211, which requires a 2" clearance to combustibles, firestopped, constructed of 4" solid masonry units and not hollow block, use a medium duty non-water soluble calcium aluminate refractory cement mixture btw flue tiles that are not eroded, deteriorated or otherwise damaged or not properly stacked one upon the other. A chimney liner is listed ONLY if there is an intact 4" wythe wall. Half this chimney is gone from the inside. The effective flue area of that 8"x8" flue is basically a 6" round or about 28 square inches. a 9" circle has an area of 63.62" square. That exterior chimney portion was so rotten they had to glue it together with Ordinary Portland Cement (OPC)-based mortar as stucco. FYI, OPC mortar and stucco tend to trap water exacerbating the erosion of the masonry as well as rotting wood-based products in contact. The water causes the soluble salts deposited over the years of acidic flue gases to migrate towards the outer wall of the chimney. Here, the efflorescence attracts water like a magnet which breaks down the masonry. The alkaline OPC mortar is converted into sand and salt, which is why most of the mortar is visibly missing from the chimney linterior. Even if you reline this chimney, there is insufficient mass to contain it (4" solid masonry units. The thimble is way too close to the combustible mudsill. The chimney connector pipe is corroded and, even new is too thin gauge for that diameter.
On top of all that, you're nursing a dinosaur boiler that is grossly inefficient. Replace the chimney with either a Class A "all-fuel" stainless steel chimney with a 316ss inner liner preferably, or type L vent. You'll have to replace all the rot, reframe/ repair the house, install listed firestops, maintain stated clearances to combustibles, use only components listed for use with that venting system, use 24ga. 316ss rigid chimney liner for your chimney connector with a barometric damper and a spill switch then install a low level CO monitor and you should be good to go.

EdTheHeaterMan · June 4

That is exactly what I said BOB. But I forgot most of technical parts. 🤣🤣🤣

PC7060 · June 4

Steam or hot water boiler?

If hot water system, consider replacing boiler with a modcon vented out side of house and abandoning/remove the chimney.

BigMak · June 5

I ended up repairing.

EdTheHeaterMan · June 5

I'm glad that my insurance company will never have to deal with this. Great DIY Job. Hope everything goes well. Just try not to let the heater run too much. Maybe only set the thermostat to 24°F if it goes that low. That should be safe maybe. No guarantees though.

As long as it looks good on the outside…. Right?

Bob Harper · June 6

What happened to the beast with the 9" flue gas outlet?

Is this a listed ss chimney liner or just pipe cemented into the base of the rotten chimney? If not a ss liner, must have a cleanout within 12" of breaching.

FYI, tape not allowed over joints on vent connector.

Still no 18" clearance to combustible ceiling or the mudsill over the CMU block wall.

I tried….

repairing a neglected chimney, flue, thimble, liner, and leaks

Comments

Categories