Hi littlealexa, Considering the age of the chimney and the number of years that it hasnÂt been used, like you, I would want to make sure that it is fit for use. A brick chimney without a liner can easily withstand the temperatures of normal fireplace use. However, the fact that it needs tuckpointing indicates that the mortar is weak and crumbling in places and the chimney structure isnÂt quite as strong as it used to be. The heating and cooling could take itÂs toll on what strength the chimney still has. Now all that is a maybe. I would think that contractor A is being cautious by recommending a liner to alleviate the effects of the heat from the chimney itself or maybe he is just out to make as much as he can. Contractor B on the other hand seems to be confident that the chimney will be OK after the tuckpointing. Why donÂt you ask contractor B for a written guarantee that you will be safe to use the fireplace with his recommendations and that he would be on the hook for any repairs if anything happened. If he balks at that idea, then heÂs not 100% sure. All this does really, is leave between a rock and a hard place on whether you should pay for piece of mind or have a nagging feeling every time you use the fireplace. The difference in costs I agree, is substantial, and before going with the high figure purely for piece of mind, I would get a couple more opinions. In fact it might not be a bad idea to have a Licensed Structural Engineer look at the chimney whereas you will at least get a signed and sealed document certifying that the chimney is structurally sound for use. Good luck, Ontario DIY guy

Hello Forum, I've got a 2-flue chimney, with fireplaces in my basement, and directly above that on the 1st floor. 1st floor is in use as a wood-burning fireplace. The basement fireplace has been closed up, and the flue has been used for the past 40 years as exhaust for the boiler. I'm replacing the boiler with a direct vent unit which will be vented directly to the side of the house. I will no longer need that flue for the boiler. We can close up the hole in the side of the chimney. Can I re-open the basement fireplace that used to be served by that flue, and use it? I don't mean do the work myself; I'd have a professional do it. My question is more based on code (I'm in NY state) and the safety of such an arrangement - are dual-flue chimneys up to code in the modern era, or are they just grandfathered in if they are still working? It would matter because we would be re-opening a fireplace that's already closed, so it would probably require a permit. Thanks in advance, Nelson

Thanks for the reply. I have decided to get a 3' stack extension with a wind trap cap on the roof. That should provide more draw. I just found out that the stack is no longer up to code. I have a large enclosure that was added on top of the roof and the top of the vent is the same height. Code requires it be 3' above the roof. I hired a chimney sweep to inspect/clean the vent to see if a bird nest or something else was blocking the vent. That's how I found out that it was not at the proper height for code. The structure was built to enclose exposed duct work. I live in a slab house that had radiant heat and was converted to central heat/AC. My neighbors have the same exposed duct work. So even though it sounds odd, it's not unusual for these 1959 slab houses. My ducts were insulated and then an enclosure was built complete with matching shingles. But that raised the roof line too close to the vent. Adding the 3' extension should do the trick right?

The International Residential Code (IRC) states that when a flue is connected to a masonry chimney the total cross sectional area of the chimney flue may be no larger than 7 times the cross sectional area of the flue connector from the device. Area equals Pi x the Radius squared and a water heater typically has a 3" connect. The Radius of 3" = 1.5" so the cross sectional area = 3.1416 (1.5 x 1.5) = 3.1416 x 2.25 = 7.06sq.in. 7 times the cross sectional area would then be 7 x 7.06sq.in = 49.42sq.in. This means the maximum allowable size of the chimney flue would be 7" x 7" Under the Uniform Plumbing code (UPC) the maximum allowable chimney flue is 4" the cross sectional area of the connector. 7.06 x 4= 28.24sq.in and the maximum allowable chimney flue size would be 5-1/4" x 5-1/4". The concern is that in mid summer the ambient air temperatures remain in the 60 to 100degF range therefore the flue will also remain in that range and even the minimal amount of heat energy from the water heater exhaust is sufficient to maintain a draft to the top of the chimney, however in winter when the ambient air temps may drop to sub -zero the temperature of the air in the flue as well as the masonry materials also drops. In this case the minimal amount of heat energy from the water heater exhaust would quickly be dissipated in the air and structural materials, thus the flue temperature would drop to a point where there is not sufficient draft to completely expel the exhaust gases out of the flue.