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Davee 12-12-2009 06:08 AM

Leaky chimney
I have a brick chimney that drips rainwater into the fireplace but only when it rains a lot and when it is windy. I installed a chimney cap and inspected the exterior bricks but cannot find where water could be seeping in. Anyone have any suggestions? Thanks.

oldognewtrick 12-13-2009 11:53 AM

davee, sounds like you have a pre-fab chimney with a metal, flat pan top to it. If so, what you may need is a new metal cap fabricated. What usually happens is the chimney insert installer will fab up a cap and nail it down to the wooden chase with 16 penny nails. Over time water will pond and the caulk on the nail heads will go away and you have a leak. At this point the cap will rust cause its probably been ponding water. If you have to replace a cap make sure it is attached from the side and crowned on top.

Now if you have a true masonry chimney thats still leaking after you put a cap on you are getting water through the mortar cap. This can be fixed by tuck pointing the mortar cap or sealing it with a masonry sealer depending on the size of any cracks. Sealers will not bridge large cracks but will act as a water shed so you don't get water soaking into the mortar.

If you can post a pic of you chimney top.

Davee 12-14-2009 03:02 PM

Leaky chimney
Thanks olddog. I wIll take some pics and post them. How do I determine if it is pre-fab or not? The house is 30 years old. Thanks.

travelover 12-14-2009 07:13 PM

Is the chimney made of bricks and mortar?

Davee 12-14-2009 11:06 PM

Yes, the chimney is made of bricks and mortar.

oldognewtrick 12-15-2009 07:06 AM

The two types of brick chimneys are brick veneer and true masonry chimneys. A brick veneer chimney starts out as a wooden structure that is framed with studs and some sort of sheeting, then a brick veneer is applied to the outside of the chase. The brick is a veneer and is not structural in nature. A metal firebox insert is installed in the bottom and a metal flue extends up through the hollow chimney chase. At the top a flat metal cap is installed to weather proof the top of the cap, it has a hole in it for the metal flue pipe to extend through. If these caps are made of galvanized metal they will usually rust. Most of the time they are nailed through the top and the nail head caulked. This will leak over prolonged exposure to the elements.

The true masonry chimney is a stone fire box with a, usually clay flue pipe that extends up with a solid brick surround. The tops where the flue pipe terminates are capped with, usually mortar. Over time moisture penetrates the mortar cap, freezes and causes cracking to occur, resulting in leaking into the structure. If you are experiencing leaking into the fire box it is most probably coming in near where the flues on either of these type chimneys terminate. A flashing or water absorption issue of the brick and mortar will usually show up in a ceiling.

Davee 12-15-2009 07:48 AM

Thanks for the information, oldog/newtrick. I believe I have the latter chimney with the clay flue. I will take pics as soon as the weather cooperates and roof dries a bit. I think there may be hairline cracks in the mortar. If that is the case, then should I take some mortar and fill in the cracks, then seal it?

drewdin 04-11-2013 06:35 PM

I have this same issue at my moms house. I wish there was an answer to this question

nealtw 04-11-2013 06:52 PM

Fire air is full off vapour and it condences in the chimney, runs down the chimney

oldognewtrick 04-12-2013 12:48 AM


Originally Posted by drewdin (Post 85940)
I have this same issue at my moms house. I wish there was an answer to this question

If you have a clay flue liner extending through the top of the chimney, there should be a cap over the top to keep rain water from falling into the firebox.

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