Reuben's Home Inspection Blog


Bad Chimneys Don't Always Need Repair

Most homes in Minneapolis and Saint Paul are old houses with masonry chimneys.  When these masonry chimneys go bad (and they all go bad) the repair can be very expensive.  If you call up a chimney contractor to see what can be done about it, they'll tell you the chimney needs repair, just like an orthodontist will tell you your kid needs braces.  Repair is just one option. The other option is removal.

Bad Chimney

When chimneys are badly deteriorated, sometimes it just makes more sense to tear the chimney down below the roof line instead of repairing the section that sticks up above the roof.  The benefits of doing this are lower repair costs, less exterior maintenance, and less chance for leakage at the roof.  Chimneys are notorious for leaks, both through the top and at the roof flashing.

Removing Chimneys

If you're thinking about tearing a chimney down below the roof line, the chimney must be located in the middle of the house.  If the chimney is located on an outside wall, the fix wouldn't simply involve removing the chimney below the roof line - it would require complete removal of the chimney, which might be cost prohibitive.  I counted houses around my neighborhood in Minneapolis (Bryn Mawr), and about three out of four houses has a chimney in the middle of the house.

To remove the chimney below the roof line, the chimney must also be abandoned, or only be used to vent gas appliances that are connected to a metal flue liner.  If the chimney is completely abandoned, it's a no-brainer; it's not doing anything, just get rid of it.

If the chimney is being used to vent gas appliances such as a furnace /  water heater / boiler, that vent will still need to penetrate the roof to carry the exhaust gases to the exterior.  Just make sure that all of the gas appliances are properly connected to the vent!

It used to be common practice to connect the furnace to a metal vent that ran inside the chimney, while the water heater would be connected only to the chimney, where it would use the annular space around the furnace vent to carry exhaust gases to the exterior.  If you see the water heater vent connector entering the chimney separately from the furnace or boiler, this is probably what is happening.  That's what you're seeing in the photo below - the smaller vent connector that I outlined in red comes from the water heater.

Water Heater Vent Connector2


The diagram below shows the same thing - click for a bigger version.


Improper Water Heater Venting

If you have an installation that looks like this, you should have it fixed, whether you plan on tearing down your chimney below the roof line or not.  Allowing the water heater to vent in to the annular space in the chimney will allow the corrosive exhaust gases to damage the chimney walls, and water heaters usually don't draft properly when they're installed this way... but I digress.  More on this topic another day.  Back to the chimney.

If the chimney is removed down below the roof line, be sure to seal up what's left of the chimney inside the attic space, to prevent the chimney from doing what it does best - bringing warm air up!  If the chimney ends below the roof line, it will act like a huge attic bypass, allowing heat to escape in to the attic.  If the chimney is abandoned, seal off the top completely.  If the chimney is still used as the chaseway for a gas vent, seal off the area between the chimney and the vent with sheet metal, and use high-temperature caulking to make it airtight.

No more chimney maintenance!

Reuben Saltzman, Structure Tech Home Inspections – Email – Bryn Mawr Home Inspections

Reuben Saltzman, Structure Tech Home Inspections


Comment balloon 13 commentsReuben Saltzman • November 24 2009 05:52AM


This is a very intersting and informative post, Reuben.  Thanks for sharing it with us.  That part about the water heater was very interesting.  I would have never dreamed to think about that.

Posted by Sharon & Bruce Walter, West Lafayette homes for sale (Keller Williams Realty Lafayette, IN) over 10 years ago

Thanks Sharon - by the time I got to the part about the improper water heater venting, I realized that was a much more common problem, and it's difficult to explain.  Perfect blog topic for another day.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 10 years ago

Great post, thanks!  I had to redo a chimney on my first house after it was under contract to be sold...ugh.

Posted by Craig Richardson (National Realty) over 10 years ago

Love that picture.

Our chimneys don't get near as bad as that one you have pictured, but I always recommend removal of abandoned chimneys when re-roofing.  I really hate to see a new roof with an abandoned chimney right in the middle of it.  I think roofers around here must not even think about it.  I recently did a house that had an abandoned chimney with a HUGE chase.  I recommended removal and use of the space for a closet or something.

Posted by Ralph Brady, The premier inspector in Humboldt (Brady Home Inspection) over 10 years ago

Good post Reuben, unless the chimney is performing some "decorative" element as well as practical function, I think removal is a great option----cures a lot of issues.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 10 years ago

Most older chimneys were built with lime mortar.  This mortar eventually turns to powder.  I removed my own chimney from above the roof, down through two stories, to the basement floor in half a day.  It had lime mortar and all I had to do was lift each brick off.  Good post with good alternatives.

Posted by David Helm, Bellingham, Wa. Licensed Home Insp (Helm Home Inspections) over 10 years ago

Craig - yuck!  

Ralph - yes, that's one of my favorites.  I like to say that chimney was being held together with inertia.  I'm glad you don't like leaving ugly chimneys in place either!

Charles - by the time chimneys get bad enough to warrant removal, they ain't decorating anything :)

David - Just half a day for the whole chimney?  That's pretty good.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 10 years ago

Didn't think about taking it down but it sounds good.

Posted by Gene Allen, Realty Consultant for Cary Real Estate (Fathom Realty) over 10 years ago

Reuben-this is a great post-very detailed and well written.  I am going to use this for a re-blog for my home owners.  Thanks!


Posted by Debbie Walsh, Hudson Valley NY Real Estate 845.283-3036 (Shahar Management) over 10 years ago

Debra - much appreciated, thanks for reading and re-blogging!

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 10 years ago
Is there a diagram of proper venting if you remove the chimney all the way to the basement and is there a preference of using PVC pipe or sheetmetal?
Posted by Steve about 9 years ago

Hi Steve, I don't have any diagrams of that, but I can tell you that you'd need to use a class B-vent, which is a double-walled metal vent.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) about 9 years ago

Why would a chimney on an outside wall require removing the entire chimney?

Posted by Brandon over 7 years ago